J. Chem. Soc., Perkin Trans. 2, 1997 1453 Chemical triggering of dioxetanes derived from 9- adamantylideneacridanes: fluoride- and base-induced chemiluminescence (CIEEL) of siloxy- and acetoxy-substituted dioxetanes Waldemar Adam* and Dirk Reinhardt Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany Photooxygenation of the methoxy-, siloxy- and acetoxy-substituted adamantylideneacridanes 3 afforded the corresponding dioxetanes 4. Thanks to the spiroadamantyl-substitution, these dioxetanes were sufficiently persistent to allow their isolation and full characterization.The activation parameters (Ea, log A, ƒH‡, ƒS‡) of the direct chemiluminescence for the methoxy-substituted derivatives 4a–c were determined by standard isothermal kinetic methods. The fluoride-ion- and base-induced decomposition of the siloxy- and acetoxy-substituted dioxetanes 4g,h,j,k was shown to involve intramolecular CIEEL emission. The CIEEL quantum yields (÷CIEEL) were independent of the nature of the protective group, but marked differences were observed between the 2- and the 3-substituted derivatives; the latter are about two orders of magnitude more efficient.The difference in the CIEEL quantum yields was attributed to the distinct fluorescence properties of the corresponding emitters 7 since fluorescence from the 2-substituted derivative 7(2) is too small to be measurable, while for the 3-substituted derivative 7(3) the fluorescence quantum yields (÷Fl) are as much as a few percent.AM1 calculations were conducted on the oxysubstituted acridone emitters 7 to explore the reasons. Presumably, the dominant charge-transfer excitation of the acridone chromophore is not appreciably perturbed by the oxy substituent for both regioisomeric emitters 7(2,3). Thus, the similar singlet excitation yields (÷S) for the regioisomeric oxysubstituted spiroacridane dioxetanes 6 generated on triggering reveal that they do not follow the odd/even rationale established for the related oxy-substituted benzoates and naphthoates.Introduction The chemiluminescence properties of dioxetanes as highenergy molecules are of particular interest for the generation of excited states, i.e. without the use of light. The formation of electronically excited products can be induced either thermally or by an electron-transfer mechanism. The latter process was originally discovered by Schuster for the dibenzoyl peroxide 1 and in the meantime abundantly documented for the a-peroxy lactones 2 and appropriate dioxetanes.3 This phenomenon of light emission has been designated as chemically initiated electron exchange luminescence (CIEEL).The CIEEL may result from both inter- and intra-molecular electron transfer. The latter case has been postulated to operate in firefly bioluminescence.4 Also 1,2-dioxetanes with substituents of low oxidation potentials, e.g. the aryl-O2 or aryl-RN2 functionalities, display intramolecular CIEEL.5–8 The most successful design 5,6 utilizes thermally persistent spiroadamantanesubstituted dioxetanes with a protected but releasable phenolate ion.The advantage of such dioxetanes is their convenient synthesis through photooxygenation. The CIEEL emission of these dioxetanes can be generated at will on treatment with an appropriate reagent (trigger), which depends on the nature of the protective group, to release the phenolate ion.The chemiexcitation step consists of the cleavage of the intermediate dioxetane phenolate anion. Such cleavage is initiated by the intramolecular electron transfer (ET) from the oxidizable phenolate functionality to the antibonding s* orbital of the peroxide bond. These phenolate-initiated, intramolecular CIEEL processes provide the basis for numerous commercial applications, most prominently in chemiluminescent immunoassays. 9 In our search for new, efficient CIEEL systems, we investigated the oxy-substituted spiroadamantane spiroacridane dioxetanes,10 protected either by silylation or by acetylation.During the triggering process, the acridone phenolates are released, which are expected to possess good fluorescence properties based on the known data of a variety of acridone derivatives. 11 Furthermore, it was of interest to assess the influence of oxy-substitution on the chemiluminescence quantum yields of the regioisomeric dioxetanes.Results Synthesis of the starting materials A convenient two-step synthesis of the adamantylideneacridanes 3a–c by starting from adamantanone and the acridanes 1a–c (Scheme 1) was developed. Addition of the in situ formed acridyllithium to adamantanone led to the alcohols 2a–c (step i), which were subsequently dehydrated to afford the methoxysubstituted olefins 3a–c (step ii). Cleavage of the ethers 3a,b by treatment with hydrobromic acid gave the phenolic olefins 3d,e (step iii), which were subsequently either silylated or acetylated to the siloxy (3g,h) (step iv) and the acetoxy (3j,k) derivatives (step v).Synthesis of the dioxetanes 4 Upon tetraphenylporphyrin (TPP)-sensitized photooxygenation of the olefins 3a–c,g,h,j,k, the hitherto unknown spiroacridane spiroadamantane dioxetanes 4 were readily obtained (step vi). The dioxetanes 4 were isolated by low-temperature, silica-gel chromatography at 210 8C, which was conducted quickly to avoid decomposition of the dioxetanes on the column.Their structure was unequivocally assigned on the basis of their spectral and analytical data and by their chemiluminescence. The 13C NMR chemical shifts of the four-membered ring carbon atoms (d 86.7–88.6 and 97.5–98.0) are characteristic for the 1,2- dioxetane structure.1454 J. Chem. Soc., Perkin Trans. 2, 1997 Scheme 1 Reagents and conditions: i, BuLi, THF, 278 to 20 8C, 24 h; ii, HOAc–H2SO4 (4 : 1), 50 to 70 8C, 30 min; iii, HBr (48%)–HOAc (1 : 1), 140 8C, 3 h; iv, ButMe2SiCl, imidazole, DMF, 40 to 50 8C, 4 h; v, Ac2O, Et3N, CH2Cl2, 20 8C, 4 h; vi, O2, TPP, hn, CDCl3, 210 8C, 30 to 45 min N CH3 OCH3 O N CH3 OH 1a–c i ii 3a–c iii + 1 4 9 OCH3 N CH3 OCH3 N CH3 OH N CH3 2a–c OAc 3d,e N CH3 1¢ OSiButMe2 5 8 3j,k N CH3 O O OR 3g,h 4a–c,g,h,j,k v iv vi a 2-OCH3 b 3-OCH3 c 4-OCH3 d 2-OH e 3-OH f 4-OH g 2-OSiButMe2 h 3-OSiButMe2 i 4-OSiButMe2 j 2-OAc k 3-OAc l 4-OAc Table 1 Rate constants a and activation parameters b for the thermal decomposition of the dioxetanes 4a–c in toluene Dioxetane 4a d 4b e 4c f T/8Cc 80.0 85.0 90.0 95.0 85.0 87.5 90.0 92.5 95.0 80.0 85.0 90.0 95.0 k/1024 s21 0.47 ± 0.05 0.88 ± 0.05 1.38 ± 0.06 2.17 ± 0.02 0.72 ± 0.01 0.92 ± 0.06 1.05 ± 0.03 1.54 ± 0.01 1.96 ± 0.06 0.44 ± 0.04 0.83 ± 0.05 1.25 ± 0.07 1.98 ± 0.05 Ea/kcal mol21 26.0 ± 0.7 26.4 ± 0.6 25.3 ± 0.6 log A 11.8 ± 0.4 12.0 ± 0.4 11.3 ± 0.3 DH‡/kcal mol21 25.3 ± 0.7 25.7 ± 0.6 24.6 ± 0.6 DS‡/cal mol21 K21 26.9 ± 1.7 26.1 ± 1.7 29.0 ± 1.3 a Calculated by first-order kinetics.b Determined by isothermal kinetics. c Temperature control within ±0.1 8C. d [4a] = 1.10 × 1023 mol dm23. e [4b] = 1.38 × 1023 mol dm23. f [4c] = 4.78 × 1023 mol dm23. Synthesis of the dioxetane decomposition products 5 The acridones 5, formed during the thermally or chemically induced dioxetane decomposition, were independently prepared (Scheme 2). Ether cleavage of the methoxy-substituted acridones 5a–c with hydrobromic acid led to the corresponding hydroxy-substituted derivatives 5d–f, which were subsequently either silylated or acetylated to the siloxy (5g–i) or the acetoxy (5j–l) acridones.These hitherto unknown compounds 5g–l were characterized on the basis of their spectral and analytical data. Chemiluminescence measurements The activation parameters for the thermal decomposition of the dioxetanes 4a–c were determined by standard isothermal kinetic methods in toluene, by monitoring the direct chemiluminescence decay photometrically.First-order (semilogarithmic) plots of the emitted light intensity versus time were perfectly linear. Arrhenius and Eyring treatment of the rate data gave the activation parameters Ea, log A and DH‡, DS‡. These results together with the k values are given in Table 1. The thermal persistence of these spiroadamantane dioxetanes isJ. Chem. Soc., Perkin Trans. 2, 1997 1455 clearly manifested by the high activation energies (Ea ca. 26 kcal mol21; 1 cal = 4.184 J). The fluoride-ion-triggered decomposition of the siloxy dioxetanes 4g,h was performed with Bu4NF in methylene chloride or acetonitrile. The base-induced decomposition of the acetoxy-substituted dioxetanes 4j,k was carried out by treatment with Bu4NOH in acetonitrile or methanol, or alternatively by sodium methanolate in methanol. Both pathways resulted in rapid decomposition with intense light emission and afforded the corresponding above-mentioned hydroxy-substituted acri- Scheme 2 Reagents and conditions: i, HBr (48%), 140 8C, 2 h; ii, ButMe2SiCl, imidazole, DMF, 40 to 50 8C, 45 h; iii, NaH, DMF, 20 8C, 1 h; iv, Ac2O, DMF, 20 8C, 30 min N CH3 OCH3 O N CH3 OH O N CH3 OSiButMe2 O N CH3 OAc O 5j–l i 5g–i 5a–c 5d–f ii iii, iv dones 5d,e.For the chemically triggered decompositions a relatively short light emission up to one minute was observed, while the thermolysis of the methoxy-substituted dioxetanes 4a–c led at elevated temperatures (T > 80 8C) to direct chemiluminescence with a continuous glow over several hours.The spectra of the chemically induced chemiluminescence matched the fluorescence spectra of the corresponding acridones 5g,h,j,k under the same conditions. The intensity–time profiles were evaluated by using first-order kinetics and the chemiluminescence yields were determined therefrom as described previously.12 The results are collected in Table 2.The reactions of the dioxetanes 4g,h,j,k with fluoride ions or with base reveal different kinetic regimes, which are dependent on the ammonium fluoride or base concentrations. With increasing concentration of the triggering agent, the CIEEL decay obeys pseudo-first-order kinetics, while at relatively low concentrations (i.e up to tenfold excess of fluoride or base) the intensity–time profiles do not fit well monoexponentially. Therefore, for proper evaluation of the kinetics, a large excess (at least twentyfold) of triggering agent is necessary since ktrigger [trigger]0 @ kET applies, i.e.the rate-determining step is the electron-transfer-induced (kET) cleavage of the dioxetane phenolate ion, while deprotection by the trigger (ktrigger[trigger] 0) is fast (Scheme 3). Then, the CIEEL decay follows pseudo-first-order kinetics. A similar behaviour was observed with other CIEEL systems, e.g. the fluoride-induced decomposition of siloxyaryl-substituted spiroadamantyl dioxetanes.13 The base-induced decomposition of the acetoxydioxetanes 4j,k was solvent dependent.For example, in methanol, somewhat smaller rate constants were obtained than in methylene chloride (cf. Table 2). The reason for this observation is found in the saponification kinetics of the ester functionality, i.e. ktrigger(RO2)[RO2]0 ! kET applies and the triggering step ktrigger(RO2)[RO2]0 is slow and, therefore, rate-determining. The siloxy and acetoxy dioxetanes with the same substitution pattern possess similar chemiluminescence quantum yields.A marked difference is observed between the 2- versus the 3- substituted derivatives, i.e. FCIEEL(4g,j) ª 1025 E mol21 versus FCIEEL(4h,k) ª 1023 E mol21. Determination of fluorescence quantum yields of the acridones 5g–1 To determine the fluorescence quantum yields of the acridone phenolate ions 7, the siloxy-substituted acridones 5g–i were Scheme 3 CIEEL mechanism of the chemically induced decomposition of the siloxy- and acetoxy-dioxetanes 4g,h,j,k N CH3 O O OSiButMe2 N CH3 O O OAc N CH3 O O O N CH3 O O O 4g,h 4j,k N CH3 O O O hn + ktrigger(F–) kET ktrigger(RO–) 6(2,3) 7(2,3)1456 J. Chem.Soc., Perkin Trans. 2, 1997 Table 2 CIEEL for the dioxetanes 4g,h,j,k and fluorescence data for the cleavage products 5g,h,j,k and the oxoacridanolates 7(2,3) Dioxetane 4g f 4h g 4j h 4ki Solvent CH2Cl2 CH3CN CH2Cl2 CH3CN CH2Cl2 CH3OH CH3OH CH2Cl2 CH3OH CH3OH Triggering agent a Bu4NF Bu4NF Bu4NF Bu4NF Bu4NOH Bu4NOH NaOMe Bu4NOH Bu4NOH NaOMe k/1023 s21 b 29.9 ± 0.3 360 ± 100 22.6 ± 3.2 25.6 ± 3.4 17.6 ± 2.8 7.0 ± 0.7 4.4 ± 0.7 21.5 ± 2.5 8.8 ± 1.3 5.4 ± 0.8 FCIEEL/1025 E mol21 c 7.2 ± 0.4 0.10 ± 0.03 350 ± 20 510 ± 50 0.62 ± 0.09 7.5 ± 0.8 5.9 ± 0.9 120 ± 10 480 ± 70 380 ± 60 FFl (5)/1022 d 95 ± 5 50 ± 5 1.0 ± 0.1 3.0 ± 0.3 14 ± 1 3.0 ± 0.3 4.0 ± 0.4 2.0 ± 0.2 FFl (7)/1022 d <0.1 <0.1 2.0 ± 0.2 1.0 ± 0.1 <0.1 <0.1 <0.1 0.7 ± 0.1 1.0 ± 0.1 0.9 ± 0.1 FS/1022 e >7 >0.1 18 ± 3 52 ± 10 >0.5 >7 >5 18 ± 4 49 ± 12 44 ± 12 a 20-fold excess of triggering agent.b k at 25 8C. c Chemiluminescence quantum yield. d Fluorescence quantum yield, relative to quinine bisulfate (FFl = 0.56, cf. ref. 26). e Quantum yield for the formation of the singlet-excited state of the free 7 derived from the acridone 5 by triggering. f [4g] = 3.28 × 1024 mol dm23. g [4h] = 6.75 × 1028 mol dm23.h [4j] = 1.68 × 1024 mol dm23. i [4k] = 1.20 × 1026 mol dm23. desilylated with the help of fluoride ions, and the acetoxysubstituted ones 5j–l saponified by means of a base (Bu4NOH or NaOMe). The acridone 5 solutions as well as the resulting oxoacridanolate 7 solutions were submitted to fluorescence analysis. The fluorescence quantum yield data for the acridones 5g,h,j,k [FFl (5)] and their corresponding oxoacridanolates 7(2,3) [FFl (7)] are given in Table 2, together with the estimated quantum yields for the formation of singlet-excited states (FS).The acridones 5 showed moderate to excellent fluorescence quantum yields. While the 2-substituted derivative 7(2) derived from the acridones 5g,j displayed a dramatic decrease in the fluorescence intensity (FFl < 0.1%), the 3-substituted derivative 7(3) derived from 5h,k remained essentially constant with moderate fluorescence yields (FFl ca. 1%). Since the 4-substituted derivative 7(4) from the acridones 5i,l showed no fluorescence at all, the synthesis of the corresponding dioxetanes was not further pursued.Discussion Spiroadamantane substitution 14 stabilizes sufficiently the labile enamine-type dioxetanes 4 to permit their isolation and characterization. The activation parameters for the dioxetanes 4a–c (Table 1) show clearly that the introduction of only one spiroadamantane moiety is enough to stabilize the dioxetane ring system against thermal decomposition. As expected, the introduction of a methoxy substituent on the acridane moiety shows no influence on the kinetics compared to the unsubstituted system. 10 The somewhat negative activation entropies obtained with the isothermal kinetic method suggest some participation of dark catalytic decomposition,15 a problem which is difficult to avoid for such enamine-type and, therefore, easily oxidizable, dioxetanes.Presumably, this chemically induced electronexchange- type decomposition is also the reason for the observed lability of these dioxetanes during the silica gel chromatographic work-up.Apparently, contact with solid surfaces promotes ion formation and catalyses electron-transfer-type decomposition.16 The siloxy- and acetoxy-substituted dioxetanes 4g,h,j,k served the purpose for chemically triggered CIEEL emission. Treatment of the siloxy derivatives with fluoride ions and the acetyl ones with base induced rapid decomposition of the dioxetanes with appreciable chemiluminescence, which was considerably higher than the light emission derived from their direct thermal decomposition. This speaks for an intramolecular electron-exchange mechanism of the CIEEL type,1–3 which yields a higher proportion of singlet-excited carbonyl products and, hence, the more intense fluorescence.In the proposed mechanism (Scheme 3), first the dioxetane phenolate ion 6 is formed, either by desilylation or by saponification, in which subsequently the electron-rich oxy anion acts as an intramolecular electron donor.After electron transfer (ET) with cleavage of the dioxetane ring, an electronically excited singlet state is generated, which manifests itself through fluorescence emission. The intensity–time profiles of the emission decay obey strict first-order kinetics in accordance with the proposed mechanism. Only the short bursts of light emission, which were obtained in the fluoride-ion-induced decomposition of dioxetane 4g in acetonitrile (cf.Table 2), are an exception. Presumably, both the deprotection as well as the electron-transfer steps are too fast for proper kinetic evaluation without time-resolved, spectral analysis. The CIEEL quantum yields in Table 2 reveal that the protecting group, i.e. whether silyl or acetyl, has no dramatic influence on the chemiluminescence efficiency. A comparison with the established spiroadamantane dioxetanes of the AMPPD type (FCIEEL up to 25%) demonstrates that the spiroacridane dioxetanes 4 are, indeed, rather inefficient CIEEL systems, especially the 2-substituted regioisomers 4g,j with chemiluminescence quantum yields in the range of 1026 to 1025 E mol21.Nevertheless, the 3-substituted derivatives 4h,k are far more effective than the 2-substituted ones. For these systems, quantum yields of up to 0.5% were obtained, which compare quite well with other CIEEL systems of the spiroadamantane type.9a The overall chemiluminescence quantum yield FCIEEL, i.e.the total number of photons emitted per number of molecules triggered, is described by eqn. (1), in which FS gives the yield of FCIEEL = FS?FFl (1) the singlet-excited-state molecules that result from the intramolecular electron-transfer pathway and FFl the fluorescence quantum yield of the oxoacridanolate 7 emitter. From this equation it is apparent that the fluorescence properties of the oxoacridanolates 7 derived from the acridones 5 (Scheme 3) may play an important role in determining the efficiency of triggered chemiluminescence (FCIEEL) of the dioxetanes 4.While the acridones 5 themselves showed moderate to excellent fluorescence quantum yields [cf. Table 2, FFl (5) 1–95%], which is expected on the basis of the known fluorescence data of acridone derivatives,11 drastic differences were encountered for the regioisomeric ions 7 generated from the dioxetanes 4 during the triggering process. Thus, in the case of the 2- substituted oxoacridanolate 7(2), the fluorescence quantum yields FFl [ 7(2)] dropped dramatically below the detection limit of our fluorescence spectrophotometer (FFl < 0.1%), whereas O O OCH3 OR AMPPD-type dioxetanes R = SiButMe2, Ac, PO3Na2, sugarJ.Chem. Soc., Perkin Trans. 2, 1997 1457 Fig. 1 Energies of the ground (S0) and the first excited singlet (S1) and triplet (T1) states as calculated by the AM1 method implemented in the VAMP 5.0 software package N CH3 O O– N CH3 O O– O– O– H3CO O H3CO O E /kcal mol–1 7(2) 7(3) -10 10 30 50 70 59 38 –7 –3 76 S0 55 T1 S1 S1 17 4 34 79 51 S0 67 –6 S1 S0 T1 T1 T1 S0 S1 –5 1 12 the values for the 3-substituted regioisomer 7(3) remained essentially constant (FFl ca. 1%). Apparently, in the crossconjugated derivative 7(2), the strong electron-donating 2-oxy anion seriously disturbs the fluorescence properties of the acridone chromophore, while for the extended-conjugated 7(3) regioisomer the relatively efficient fluorescence ability is retained.Thus, in view of eqn. (1), a direct response exists between the poor triggered-chemiluminescence efficiencies (FCIEEL) and the essentially non-fluorescent 2-substituted emitter 7(2), on the one hand, and the quite good triggeredchemiluminescence quantum yields and the moderate fluorescent 3-substituted emitter 7(3), on the other hand. With the fluorescence quantum yields of the emitters 7 available, according to eqn. (1), the singlet excitation yields (FS) for the chemically induced decomposition of the dioxetanes 4g,h,j,k may be estimated.For the 3-substituted dioxetanes N CH3 O N CH3 O O O N CH3 O O N CH3 O O Crossed conjugation (odd substitution) Extended conjugation (even substitution) 7(2) 7(3) even odd 4h,k, the singlet excitation yields were found to range between 18 and 52% (cf. Table 2). As already pointed out, for the 2- substituted dioxetanes 4g,j only upper limits (fluorescence detection limit ca. 0.1%) for the fluorescence yields of the corresponding oxoacridanolate 7(2) have been established, such that for these dioxetanes only lower limiting values of FS may be obtained in Table 2. These estimated FS data suggest that the yield of singlet-excited molecules is about an order of magnitude lower for the cross-conjugated 2-substituted 4g,j versus the extended-conjugated 3-substituted 4h,k regioisomers. However, this constitutes the maximum difference in the FS values for these two sets of regioisomers since the FFl values may very well be substantially lower than the upper limit taken at ca. 0.1%, our detection limit. Consequently, it may very well be that the 2- and 3-substituted regioisomeric acridone dioxetanes 4 possess a similar capacity to generate singlet-excited states on CIEEL triggering. During the development of the first efficient CIEEL-active spiroadamantane dioxetanes,5,6 a significant dependence of the chemiluminescence quantum yields (FCIEEL) on the substitution pattern was established.In the case of acetoxynaphthyl spiroadamantyl dioxetanes, Bronstein et al.17 observed empirically that extended-conjugated carbonyl chromophores derived from dioxetanes during triggered decomposition gave rise to flashlike emission, accompanied by low chemiexcitation efficiencies, whereas cross-conjugated carbonyl compounds exhibited a steady glow with higher quantum yields. The authors 17 postulated a so-called odd/even rationale to explain this empirical phenomenon: charge transfer from the donor (phenolate) to the acceptor (carbonyl group) occurs more effectively when the two groups are cross-conjugated (an odd number of carbon atoms between the interacting groups), as substantiated by semiempirical MO calculation.Presumably, charge transfer enhances excited-state formation, ensures high chemiexcitation efficiencies and provides a persistent glow through stabilization of the incipient excited state.In contrast, extended conjugation stabilizes the ground state through dipolar resonance, which disfavours excited-state formation and, consequently, low efficiencies and short flashes are observed.17,181458 J. Chem. Soc., Perkin Trans. 2, 1997 Application of this odd/even rationale on our spiroacridane system 4 and, if as a first approximation, the electronic influence of the methylamino functionality is neglected, one would expect the cross-conjugated 2-regioisomer to be more efficient in its light emission than the extended-conjugated 3- regioisomer; however, experimentally quite the contrary is observed (Table 2).Therefore, to assess how the oxy-anion substituent affects the ground and excited states of the regioisomeric ions 7(2,3), AM1 calculations were conducted. The computed energies of the ground and the first excited singlet and triplet states of the regioisomeric ions 7(2,3) are shown in Fig. 1, and for comparison also the oxybenzoate regioisomers.Analogous to the latter reference system, the energy gap between the first excited singlet states of 7(2) and 7(3) was computed to be 17 kcal mol21 lower for the 7(2) regioisomer, which elucidates that the first excited singlet state is stabilized by 2-oxy more effectively than by 3-oxy substitution. However, in contrast to the oxybenzoate reference system, the ground state is also stabilized by the 2-oxy substituent since the energy gap between 7(2) and 7(3) was calculated to be ca. 4 kcal mol21 again in favour of the 7(2) regioisomer. Therefore, the odd/even rationale is not valid for this particular acridone system, which establishes that the singlet-excited state of the cross-conjugated regioisomer 7(2) is stabilized while it is the ground state for the extended-conjugated 7(3) regioisomer. The calculated singlet energies for the two regioisomers of 7 are in good agreement with the experimental UV absorption spectra, i.e.the observed absorption maxima (lmax) are located at ca. 435 for 7(2) and ca. 370 nm for 7(3), while the AM1-calculated ones are at 437 and 361 nm. Furthermore, the calculations revealed that the amount of charge transfer from the donor (phenolate) to the acceptor (benzoyl group) is more or less independent of the substitution pattern, which was confirmed by configurationinteraction calculations. The charge density distributions for the excitation of the oxoacridanolates 7 are shown in Fig. 2, Fig. 2 Charge-density distributions for the ground (bottom) and the first excited states (top) of the regioisomeric oxoacridanolates 7 N Me O O N Me O O N Me O O N Me O O 7(2) 7(3) 0.08 0.09 0.15 0.15 0.12 0.26 0.05 0.06 0.20 0.15 0.28 0.14 0.06 0.31 0.19 0.17 0.22 0.17 0.17 0.25 0.06 0.20 O O H3CO O H3CO O O H3CO O meta O H3CO O para 0.16 0.33 0.10 0.07 0.10 0.18 0.13 0.29 0.14 0.15 0.13 0.08 0.23 0.22 0.29 0.22 0.21 0.17 0.21 0.33 0.05 Fig. 3 Charge-density distributions for the ground (bottom) and the first excited states (top) of the regioisomeric oxybenzoates and for comparison also the oxybenzoate regioisomers in Fig. 3. The first excited singlet as well as triplet state wave functions are mainly composed of HOMO and LUMO contributions, which are both of the p-type. In the excitation step of the acridone system, charge is transferred from the phenolate to the benzoyl moiety. The amount of charge transfer is essentially independent of the oxy-substitution (Fig. 2). In comparison, the charge distributions for the regioisomeric oxybenzoates show a definite dependence on the substitution pattern, i.e. charge transfer occurs more effectively for the meta regioisomer (Fig. 3), as it was proposed in the odd/even rationale.17 Therefore, as already pointed out, this rationale is not valid for the oxoacridinolates 7. Apparently, the charge-transfer character of the excited oxoacridinolate 7* chromophore,19 as expected for a vinylogous amide, is the main electronic characteristic of 7 [eqn.(2)]. Thus, the introduction of an additional oxy substituent, whether in the 2- or 3-positions of the excited oxoacridanolates 7(2,3), does not perturb significantly this chargetransfer transition. In summary, we have demonstrated that the CIEEL-active spiroacridane spiroadamantane 1,2-dioxetanes undergo fluoride-ion- or base-triggered decomposition with appreciable chemiluminescence. The substitution pattern plays a significant role in regard to the relative FCIEEL values, as exhibited by the chemiluminescence quantum data in Table 2.The efficiency of the chemically induced chemiluminescence is dictated by the markedly different fluorescence properties of the corresponding oxoacridanolate emitters (Table 2), with high fluorescence yields for the 3-oxy- 7(3) and unexpectedly low ones for the 2- oxy-substituted 7(2) regioisomers. This unusual fluorescence behaviour requires further elucidation.Experimental General 1H and 13C NMR spectra were measured on a Bruker AC 200 (1H: 200 MHz, 13C: 50 MHz) or a Bruker QF 600 spectrometer (1H: 600 MHz, 13C: 151 MHz) with deuteriochloroform, [2H6]dimethyl sulfoxide or [2H4]methanol as internal standards. J values are given in Hz. IR spectra were recorded on a Perkin- Elmer 1420 Ratio Recording IR spectrophotometer, UV spectra on a Hitachi U-3200 spectrophotometer, and fluorescence spectra on a Perkin-Elmer LS50 spectrofluorimeter.Elemental analyses were carried out by the Microanalytic Division of the Institute of Inorganic Chemistry, University of Würzburg. Melting points were taken on a Büchi apparatus B-545 and are not corrected. TLC analysis was conducted on precoated silica gel foils Polygram SIL G/UV254 (40 × 80 mm) from Macherey and Nagel. Spots were identified under a UV lamp and dioxetanes additionally by heating (short flash). Silica gel (63–200 mm; Woelm) was used for column chromatography, the adsorbance : substrate ratio was ca. 100 : 1. Low-temperature chromatography was performed on a column equipped with a vacuumjacketed cooling mantle through which refrigerant was circulated from a RK 20 Lauda Cryomat. All kinetic measurements were performed on a Mitchell- Hastings photometer 20 equipped with a RCA 926 B photomultiplier and a Lauda thermostat K 20 for temperature control of the cell compartment. Beckmann scintillation vials were used as reaction vessels.A Servogor Z10 recorder registered the output signal of the kinetic run. N CH3 O N CH3 O– 7(2,3) O– O– hn 7*(2,3) CT (2)J. Chem. Soc., Perkin Trans. 2, 1997 1459 Starting materials The acridanes 1a–c 21 were prepared according to the literature procedure 22 by reduction of the corresponding acridones 5a– c 23,24 with sodium in refluxing isopentyl alcohol. The physical and spectral data of these compounds were consistent with those reported.21 General procedure for the synthesis of the adamantanols 2a–c.To a cooled solution (278 8C) of the acridane 1 (ca. 0.01 mmol) in dry tetrahydrofuran (THF) (100 cm3) was added under nitrogen butyllithium (5 equiv., 1.3–1.6 mol dm23 in hexane). The solution turned red. After stirring at 0 8C for 30 min and subsequent cooling to 278 8C, a solution of adamantanone (1.1 equiv.) in dry THF (50 cm3) was added, followed by stirring at ca. 20 8C for 24 h. The solution was poured into aqueous sodium hydrogen carbonate (100 cm3) and extracted with THF (3 × 50 cm3).The extract was dried (MgSO4) and evaporated to dryness. Chromatography on silica gel with methylene chloride as the eluent yielded the adamantanols 2a–c. 2-(2-Methoxy-10-methylacridan-9-yl)adamantan-2-ol (2a).— By following the above procedure, from the acridane 1a (3.00 g, 13.3 mmol), BuLi (40 cm3, 64.0 mmol) and adamantanone (2.20 g, 14.6 mmol) the adamantanol 2a was obtained as paleyellow needles (3.35 g, 67%), mp 156.0–156.5 8C, Rf(CH2Cl2) 0.36 (Found: C, 79.59; H, 8.07; N, 3.87. C25H29NO2 requires C, 79.96; H, 7.78; N, 3.73%); nmax(KBr)/cm21 3500–3250 (OH), 2940, 2880, 2840, 1470; dH(200 MHz; CDCl3) 0.90–2.40 (14 H, m, Ad-H), 3.31 (3 H, s, 10-CH3), 3.78 (3 H, s, 2-OCH3), 4.63 (1 H, s, 9-H), 6.79–6.99 (5 H, m, 1-H, 3-H, 4-H, 5-H and 7-H) and 7.19–7.29 (2 H, m, 6-H and 8-H); dC(50 MHz; CDCl3) 27.0 (d), 27.7 (d), 32.9 (2d), 33.0 (t), 33.2 (t), 33.7 (q), 34.6 (t), 34.9 (t), 38.4 (t), 46.7 (d), 55.7 (q), 80.1 (s), 112.0 (d), 112.5 (d), 113.3 (d), 115.6 (d), 120.3 (d), 123.3 (s), 125.2 (s), 127.3 (d), 129.6 (d), 138.6 (s), 144.8 (s) and 154.1 (s). 2-(3-Methoxy-10-methylacridan-9-yl)adamantan-2-ol (2b).— By following the above procedure, from the acridane 1b (3.47 g, 15.4 mmol), BuLi (55 cm3, 77.0 mmol) and adamantanone (2.54 g, 16.9 mmol) the adamantanol 2b was obtained as a colourless powder (4.26 g, 74%), mp 80–82 8C, Rf(CH2Cl2) 0.40 (Found: C, 79.85; H, 8.04; N, 3.64.C25H29NO2 requires C, 79.96; H, 7.78; N, 3.73%); nmax(KBr)/cm21 3440–3300 (OH), 2930, 2880, 2830, 1580, 1460; dH(200 MHz; CDCl3) 0.90–2.40 (14 H, m, Ad-H), 3.33 (3 H, s, 10-CH3), 3.82 (3 H, s, 3-OCH3), 4.62 (1 H, s, 9-H), 6.53–6.57 (2 H, m, 2-H and 4-H), 6.94–7.01 (2 H, m, 5-H and 7-H), 7.12 (1 H, m, 1-H) and 7.20–7.29 (2 H, m, 6-H and 8-H); dC(50 MHz; CDCl3) 27.0 (d), 27.7 (d), 32.9 (2d), 33.2 (2t), 33.6 (q), 34.6 (t), 34.8 (t), 38.3 (t), 45.5 (d), 55.3 (q), 79.8 (s), 99.8 (d), 105.1 (d), 112.8 (d), 116.0 (s), 120.6 (d), 123.9 (s), 127.2 (d), 129.7 (d), 130.2 (d), 144.2 (s), 145.3 (s) and 159.2 (s). 2-(4-Methoxy-10-methylacridan-9-yl)adamantan-2-ol (2c).— By following the above procedure, from the acridane 1c (3.00 g, 13.3 mmol), BuLi (40 cm3, 64.0 mmol) and adamantanone (2.20 g, 14.6 mmol) the adamantanol 2c was obtained as a yellow viscous oil that solidified after some days (3.82 g, 76%), mp 52–54 8C, Rf(CH2Cl2) 0.45 (Found: C, 79.72; H, 7.59; N, 3.89.C25H29NO2 requires C, 79.96; H, 7.78; N, 3.73%); nmax(KBr)/ cm21 3500–3300 (OH), 2940, 2900, 2840, 1635, 1595, 1530, 1490; dH(200 MHz; CDCl3) 0.90–2.40 (14 H, m, Ad-H), 3.58 (3 H, s, 10-CH3), 3.83 (3 H, s, 4-OCH3), 4.58 (1 H, s, 9-H), 6.79–6.83 (2 H, m, 1-H and 3-H), 6.89–6.98 (2 H, m, 2-H and 7-H), 7.08– 7.15 (2 H, m, 5-H and 8-H) and 7.19–7.28 (1 H, m, 6-H); dC(50 MHz; CDCl3) 27.0 (d), 27.6 (d), 32.9 (t), 33.2 (t), 33.4 (d), 33.7 (d), 34.5 (2t), 38.3 (t), 39.6 (q), 46.3 (d), 55.8 (q), 77.9 (s), 110.9 (d), 115.5 (d), 120.4 (d), 121.5 (d), 122.3 (d), 125.8 (s), 127.0 (d), 128.1 (s), 129.1 (d), 133.9 (s), 146.8 (s) and 150.8 (s).General procedure for the synthesis of the methoxy olefins 3a– c. A solution of the adamantanol 2a–c (ca. 7–8 mmol) in glacial acetic acid–sulfuric acid (4 : 1) (20 cm3) was stirred at 50–70 8C for 30 min. After diluting with water (20 cm3), the solution was extracted with methylene chloride (4 × 10 cm3).The extract was washed with aqueous sodium hydrogen carbonate (2 × 20 cm3), dried (MgSO4), and evaporated to dryness at 20 8C and 10 Torr. Chromatography of the residue on silica gel with methylene chloride and, if necessary, other eluents afforded the olefins 3a–c. 9-Adamantylidene-2-methoxy-10-methylacridane (3a).—Dehydration of the adamantanol 2a (2.50 g, 6.66 mmol) yielded the olefin 3a as colourless needles (1.40 g, 59%), mp 190– 191 8C, Rf(light petroleum–diethyl ether, 20 : 1) 0.50 (Found: C, 84.06; H, 7.60; N, 3.66. C25H27NO requires C, 83.99; H, 7.61; N, 3.92%); nmax(KBr)/cm21 2880, 2820, 1485, 1455, 1260, 1230; dH(200 MHz; CDCl3) 1.50–2.20 (12 H, m, Ad-H), 3.37 (3 H, s, 10-CH3), 3.46 (1 H, br s, 19-H), 3.53 (1 H, br s, 19-H), 3.79 (3 H, s, 2-OCH3), 6.74–6.99 (5 H, m, 1-H, 3-H, 4-H, 5-H and 7-H) and 7.16–7.24 (2 H, m, 6-H and 8-H); dC(50 MHz; CDCl3) 28.0 (2d), 32.2 (d), 32.4 (d), 33.4 (q), 37.1 (t), 39.7 (4t), 55.7 (q), 111.2 (d), 111.7 (d), 112.3 (d), 113.3 (d), 119.6 (d), 120.3 (s), 125.6 (s), 126.3 (d), 127.2 (d), 127.3 (s), 139.3 (s), 144.5 (s), 145.2 (s) and 153.7 (s). 9-Adamantylidene-3-methoxy-10-methylacridane (3b).—Dehydration of the adamantanol 2b (3.00 g, 8.00 mmol) yielded the olefin 3b as colourless needles (1.37 g, 48%), mp 168–169 8C (Found: C, 84.10; H, 7.54; N, 3.59. C25H27NO requires C, 83.99; H, 7.61; N, 3.92%); nmax(KBr)/cm21 2880, 2820, 1580, 1450; dH(200 MHz; CDCl3) 1.60–2.20 (12 H, m, Ad-H), 3.39 (3 H, s, 10-CH3), 3.46 (2 H, br s, 19-H), 3.84 (3 H, s, 3-OCH3), 6.54–6.59 (2 H, m, 2-H and 4-H), 6.95–7.02 (2 H, m, 5-H and 7-H) and 7.13–7.27 (3 H, m, 1-H, 6-H and 8-H); dC(50 MHz; CDCl3) 28.1 (2d), 32.2 (2d), 33.4 (q), 37.2 (t), 39.2 (4t), 55.3 (q), 99.1 (d), 104.4 (d), 112.0 (d), 119.4 (s), 119.7 (s), 120.0 (d), 126.1 (d), 126.4 (s), 127.1 (d), 127.8 (d), 143.2 (s), 144.7 (s), 146.1 (s) and 158.5 (s). 9-Adamantylidene-4-methoxy-10-methylacridane (3c).—Dehydration of the adamantanol 2c (2.90 g, 7.72 mmol) yielded the olefin 3c as colourless needles (1.65 g, 60%), mp 172–173 8C, Rf(light petroleum–diethyl ether 5 : 1) 0.70 (Found: C, 83.90; H, 7.88; N, 3.75.C25H27NO requires C, 83.99; H, 7.61; N, 3.92%); nmax(CCl4)/cm21 2880, 2820, 1430, 1250; dH(200 MHz; CDCl3) 1.60–2.20 (12 H, m, Ad-H), 3.40 (1 H, br s, 19-H), 3.46 (1 H, br s, 19-H), 3.67 (3 H, s, 10-CH3), 3.82 (3 H, s, 4-OCH3), 6.76 (1 H, dd, J3,2 7.6 and J3,1 1.7, 3-H), 6.84 (1 H, dd, J1,2 7.6 and J1,3 1.7, 1-H), 6.93 (1 H, dd, J2,1 and J2,3 7.6, 2-H), 6.94 (1 H, m, 7-H), 7.07–7.18 (2 H, m, 5-H and 8-H) and 7.19 (1 H, ddd, J6,5 8.3, J6,7 7.0 and J6,8 1.5, 6-H); dC(50 MHz; CDCl3) 28.1 (2d), 32.1 (d), 32.5 (d), 37.2 (t), 38.8 (q), 39.2 (4t), 56.1 (q), 110.5 (d), 113.7 (d), 119.8 (d), 120.3 (d), 120.8 (s), 120.9 (d), 126.0 (d), 126.7 (d), 127.9 (s), 130.8 (s), 133.8 (s), 143.6 (s), 146.9 (s) and 150.4 (s).General procedure for the synthesis of the hydroxy olefins 3d,e. A solution of methoxy olefin 3a,b (ca. 0.2–0.6 mmol) in hydrobromic acid (48%)–glacial acetic acid (1 : 1) (20 cm3) was kept at reflux for 3 h. By addition of water (20 cm3), the hydroxy olefins 3d,e precipitated and were dried over P2O5 at 20 8C and 10 Torr. 9-Adamantylidene-2-hydroxy-10-methylacridane (3d).—Demethylation of the methoxy olefin 3a (207 mg, 0.579 mmol) yielded the hydroxy olefin 3d as an orange powder (82.0 mg, 41%), mp 184 8C (Found: C, 84.03; H, 7.46; N, 3.98. C24H25NO requires C, 83.93; H, 7.34; N, 4.08%); nmax(KBr)/cm21 3600– 3000 (OH), 2920, 2870, 1635, 1565, 1495, 1260; dH(200 MHz; CD3OD) 1.66–1.82 (10 H, m, Ad-H), 2.11 (2 H, m, Ad-H), 2.43 (1 H, m, Ad-H), 2.80 (1 H, m, Ad-H), 4.77 (3 H, s, 10-CH3), 7.84 (1 H, ddd, J7,8 9.0, J7,6 6.7 and J7,5 1.0, 7-H), 7.89 (1 H, dd, J3,4 9.7 and J3,1 2.6, 3-H), 7.99 (1 H, d, J1,3 2.6, 1-H), 8.18 (1 H, ddd, J6,5 9.2, J6,7 6.7 and J6,8 1.2, 6-H), 8.53 (1 H, dd, J5,6 9.2 and J5,7 1.0, 5-H), 8.54 (1 H, d, J4,3 9.7, 4-H) and 8.79 (1 H, dd, J8,7 9.0 and J8,6 1.2, 8-H); dC(50 MHz; CD3OD) 28.8 (d), 28.9 (d), 34.4 (2d), 37.8 (t), 38.2 (2t), 40.2 (t), 40.8 (t), 52.4 (q), 108.3 (d), 119.6 (d), 121.5 (d), 127.6 (d), 128.2 (s), 128.8 (d), 128.8 (s), 130.1 (s), 131.9 (d), 137.0 (d), 138.1 (s), 140.8 (s), 157.3 (s) and 166.0 (s).1460 J.Chem. Soc., Perkin Trans. 2, 1997 9-Adamantylidene-3-hydroxy-10-methylacridane (3e).—Demethylation of the methoxy olefin 3b (72.0 mg, 0.201 mmol) yielded the hydroxy olefin 3e as a yellow powder (66.0 mg, 96%), mp 160–161 8C (Found: C, 83.61; H, 6.98; N, 3.99.C24H25NO requires C, 83.93; H, 7.34; N, 4.08%); nmax(KBr)/ cm21 3480–3280 (OH), 2900, 2830, 1610, 1590, 1450, 1225; dH(200 MHz; CD3OD) 1.66–1.82 (10 H, m, Ad-H), 2.08 (2 H, m, Ad-H), 2.43 (1 H, m, Ad-H), 2.77 (1 H, m, Ad-H), 4.54 (3 H, s, 10-CH3), 7.42 (1 H, dd, J2,1 9.8 and J2,4 2.3, 2-H), 7.50 (1 H, d, J4,2 2.3, 4-H), 7.79 (1 H, ddd, J7,8 8.8, J7,6 6.9 and J7,5 1.0, 7-H), 8.16 (1 H, ddd, J6,5 9.1, J6,7 6.9 and J6,8 1.2, 6-H), 8.42 (1 H, dd, J5,6 9.1 and J5,7 1.0, 5-H), 8.69 (1 H, dd, J8,7 8.8 and J8,6 1.2, 8-H) and 8.77 (1 H, d, J1,2 9.8, 1-H); dC(50 MHz; CD3OD) 28.8 (d), 29.1 (d), 34.3 (2d), 37.8 (t), 38.4 (t), 38.7 (t), 40.7 (2t), 52.1 (q), 100.2 (d), 100.6 (d), 119.1 (d), 121.4 (d), 123.2 (s), 126.5 (s), 127.6 (s), 129.1 (d), 132.9 (d), 137.1 (d), 141.9 (s), 146.3 (s), 154.6 (s) and 168.3 (s).General procedure for the synthesis of the siloxy olefins 3g,h.A solution of the hydroxy olefin 3d,e (ca. 0.1 mmol), tertbutyldimethylchlorosilane (1.5 equiv.) and imidazole (2.0 equiv.) in dry dimethylformamide (DMF) (5 cm3) was stirred at 40–50 8C for 4 h. Subsequently, the solution was poured into water (5 cm3) and extracted with diethyl ether (2 × 5 cm3) and methylene chloride (5 cm3). The extract was washed with water (5 cm3), dried (MgSO4), and evaporated to dryness at 20 8C and 10 Torr. Chromatography of the residue with methylene chloride and light petroleum–diethyl ether (20 : 1) as the eluents afforded the siloxy olefins 3g,h. 9-Adamantylidene-2-(tert-butyldimethylsiloxy)-10-methylacridane (3g).—By following the above procedure, from the hydroxy olefin 3d (36.0 mg, 0.105 mmol), tert-butyldimethylchlorosilane (24.0 mg, 0.159 mmol) and imidazole (14.0 mg, 0.206 mmol) the siloxy olefin 3g was obtained as a colourless powder (34.0 mg, 71%), mp 129–130 8C, Rf(light petroleum– diethyl ether 20 : 1) 0.70 (Found: C, 78.88; H, 8.13; N, 2.98.C30H39NOSi requires C, 78.72; H, 8.59; N, 3.06%); nmax(KBr)/ cm21 2930, 2910, 2880, 2830, 1450, 1260; dH(200 MHz; CDCl3) 0.18 (6 H, s, SiMe2), 0.98 (9 H, s, SiCMe3), 1.40–2.20 (12 H, m, Ad-H), 3.36 (3 H, s, 10-CH3), 3.45 (1 H, br s, 19-H), 3.52 (1 H, br s, 19-H), 6.69 (1 H, dd, J3,4 8.6 and J3,1 2.6, 3-H), 6.74 (1 H, d, J1,3 2.6, 1-H), 6.81 (1 H, d, J4,3 8.6, 4-H), 6.92–7.00 (2 H, m, 5-H and 7-H) and 7.15–7.25 (2 H, m, 6-H and 8-H); dC(50 MHz; CDCl3) 24.4 (2q), 18.2 (s), 25.8 (3q), 27.9 (2d), 32.2 (2d), 33.3 (q), 37.1 (t), 38.2 (4t), 111.7 (d), 112.3 (d), 117.6 (d), 118.5 (d), 119.5 (d), 120.2 (s), 120.6 (s), 125.7 (s), 126.2 (d), 127.2 (d), 139.4 (s), 144.1 (s), 145.2 (s) and 149.2 (s). 9-Adamantylidene-3-(tert-butyldimethylsiloxy)-10-methylacridane (3h).—By following the above procedure, from the hydroxy olefin 3e (30.0 mg, 87.3 mmol), tert-butyldimethylchlorosilane (20.0 mg, 0.133 mmol) and imidazole (12.0 mg, 0.176 mmol) the siloxy olefin 3h was obtained as a colourless powder (15.0 mg, 38%), mp 114–115 8C, Rf(light petroleum– diethyl ether 20 : 1) 0.30 (Found: C, 79.17; H, 8.57; N, 2.76.C30H39NOSi requires C, 78.72; H, 8.59; N, 3.06%); nmax(KBr)/ cm21 2940, 2900, 2830, 1580, 1450; dH(200 MHz; CDCl3) 0.21 (6 H, s, SiMe2), 0.99 (9 H, s, SiCMe3), 1.50–2.20 (12 H, m, Ad-H), 3.35 (3 H, s, 10-CH3), 3.43 (2 H, br s, 19-H), 6.44–6.49 (2 H, m, 2-H and 4-H), 6.93–7.07 (3 H, m, 1-H, 5-H and 7-H) and 7.15– 7.23 (2 H, m, 6-H and 8-H); dC(50 MHz; CDCl3) 24.3 (2q), 18.2 (s), 25.7 (3q), 28.1 (2d), 32.1 (2d), 33.3 (q), 37.1 (t), 39.2 (4t), 104.3 (d), 111.3 (d), 111.9 (d), 119.6 (s), 119.8 (s), 119.9 (d), 126.1 (d), 126.4 (s), 127.2 (d), 127.7 (d), 143.1 (s), 144.7 (s), 146.0 (s) and 154.3 (s).General procedure for the synthesis of the acetoxy olefins 3j,k. The hydroxy olefin 3d,e (1 equiv.) was suspended in methylene chloride (10 cm3), triethylamine (1.1 equiv.) and, subsequently, acetic anhydride (1.1 equiv.) were added and the solution was stirred for 24 h.After the addition of water (10 cm3), the solution was extracted with diethyl ether (2 × 10 cm3), the extract was washed with 10% HCl (10 cm3), aqueous sodium hydrogen carbonate (10 cm3) and water (10 cm3), dried (MgSO4), and evaporated to dryness at 20 8C and 10 Torr. Chromatography of the residue with methylene chloride and light petroleum–diethyl ether as the eluents afforded the acetoxy olefins 3j,k. 2-Acetoxy-9-adamantylidene-10-methylacridane (3j).—By following the above procedure, from the hydroxy olefin 3d (279 mg, 0.812 mmol), triethylamine (130 mm3, 0.938 mmol) and acetic anhydride (90.0 mm3, 0.952 mmol) the acetoxy olefin 3j was obtained as a colourless powder (184 mg, 59%), mp 85– 87 8C, Rf(light petroleum–diethyl ether 5 : 1) 0.30 (Found: C, 81.08; H, 6.92; N, 3.24. C26H27NO2 requires C, 81.01; H, 7.06; N, 3.63%); nmax(KBr)/cm21 2880, 2820, 1740 (CO), 1200, 1185; dH(200 MHz; CDCl3) 1.50–2.20 (12 H, m, Ad-H), 2.30 (3 H, s, COCH3), 3.39 (3 H, s, 10-CH3), 3.44 (2 H, br s, 19-H), 6.92–7.01 (5 H, m, 1-H, 3-H, 4-H, 5-H and 7-H) and 7.16–7.26 (2 H, m, 6- H and 8-H); dC(50 MHz; CDCl3) 21.2 (q), 27.4 (2d), 32.1 (d), 32.2 (d), 33.4 (q), 37.1 (t), 39.2 (4t), 111.9 (d), 112.2 (d), 118.9 (d), 119.7 (s), 120.0 (d), 120.1 (d), 125.6 (s), 126.4 (d), 126.9 (s), 127.2 (d), 142.8 (s), 144.1 (s), 144.7 (s), 145.1 (s) and 170.0 (s). 3-Acetoxy-9-adamantylidene-10-methylacridane (3k).—By following the above procedure, from the hydroxy olefin 3e (20.0 mg, 58.2 mmol), triethylamine (10.0 mm3, 72.1 mmol) and acetic anhydride (7.00 mm3, 74.0 mmol) the acetoxy olefin 3k was obtained as a colourless powder (17.0 mg, 76%), mp 150– 152 8C, Rf(light petroleum–diethyl ether 20 : 1) 0.20 (Found: C, 81.23; H, 6.76; N, 3.56. C26H27NO2 requires C, 81.01; H, 7.06; N, 3.63%); nmax(KBr)/cm21 2880, 2820, 1730 (CO), 1450, 1200, 1180; dH(200 MHz; CDCl3) 1.60–2.20 (12 H, m, Ad-H), 2.31 (3 H, s, COCH3), 3.37 (3 H, s, 10-CH3), 3.43 (2 H, br s, 19-H), 6.68–6.73 (2 H, m, 2-H and 4-H), 6.94–7.02 (2 H, m, 5-H and 7- H) and 7.16–7.24 (3 H, m, 1-H, 6-H and 8-H); dC(50 MHz; CDCl3) 21.2 (q), 27.4 (2d), 32.2 (2d), 33.4 (q), 37.1 (t), 39.2 (4t), 105.6 (d), 112.0 (d), 112.8 (d), 119.5 (s), 120.3 (d), 123.8 (s), 126.0 (s), 126.3 (d), 127.2 (d), 127.6 (d), 144.5 (s), 144.6 (s), 145.9 (s), 149.2 (s) and 169.7 (s).Photooxygenation of the olefins 3a–c,g,h,j,k. Into a 10 cm3 test tube, equipped with gas inlet and outlet tubes and a UV filter, was placed a solution of the corresponding olefin 3 (26.0– 117 mmol) and a few crystals of tetraphenylporphyrin (TPP) in CDCl3 (0.7–3.0 cm3).The solution was cooled to 210 8C and a gentle stream of dry oxygen gas was passed through the solution while irradiating with two 150 W sodium lamps (Philips G/98/2-SON). The reaction progress was monitored by TLC and 1H NMR spectroscopy. After complete consumption of the starting material, the dioxetanes 4 were isolated by lowtemperature chromatography on silica gel at 210 8C with light petroleum–diethyl ether (5 : 1) as the eluent.At temperatures higher than 60 8C, decomposition of all dioxetanes took place (cf. below: determination of the activation parameters for the thermal decomposition of the dioxetanes 4a–c). 2-Methoxy-10-methyldispiro[acridane-9,39-[1,2]dioxetane- 49,20-adamantane] (4a).—Photooxygenation of the olefin 3a (10.0 mg, 28.0 mmol) in CDCl3 (0.7 cm3) for 30 min gave the dioxetane 4a as a yellow, amorphous powder (4.90 mg, 45%), Rf(light petroleum–diethyl ether 5 : 1) 0.52 (Found: C, 77.01; H, 6.49; N, 3.33. C25H27NO3 requires C, 77.09; H, 6.99; N, 3.60%); nmax(CDCl3)/cm21 2910, 2890, 2840, 1585, 1490, 1460, 1265; dH(200 MHz; CDCl3) 0.90–2.00 (12 H, m, Ad-H), 2.27 (1 H, br s, 19-H), 2.32 (1 H, br s, 19-H), 3.44 (3 H, s, 10-CH3), 3.89 (3 H, s, 2-OCH3), 6.97 (3 H, m, 3-H, 4-H and 5-H), 7.14 (1 H, ddd, J7,8 and J7,6 7.6 and J7,5 1.0, 7-H), 7.38 (1 H, ddd, J6,5 7.7, J6,7 7.6 and J6,8 1.6, 6-H), 7.75 (1 H, d, J1,3 2.5, 1-H) and 8.15 (1 H, dd, J8,7 7.6 and J8,6 1.6, 8-H); dC(50 MHz; CDCl3) 25.5 (d), 25.7 (d), 30.9 (2t), 31.7 (2d), 32.9 (2t), 33.0 (q), 36.2 (t), 55.9 (q), 87.6 (s), 98.0 (s), 111.4 (d), 112.1 (d), 112.7 (d), 115.7 (d), 119.8 (d), 120.9 (s), 124.5 (s), 127.9 (d), 129.0 (d), 133.5 (s), 140.8 (s) and 153.9 (s). 3-Methoxy-10-methyldispiro[acridane-9,39-[1,2]dioxetane- 49,20-adamantane] (4b).—Photooxygenation of the olefin 3b (12.3 mg, 24.4 mmol) in CDCl3 (0.7 cm3) for 30 min gave theJ.Chem. Soc., Perkin Trans. 2, 1997 1461 dioxetane 4b as a yellow, amorphous powder (9.00 mg, 67%), Rf(light petroleum–diethyl ether 5 : 1) 0.33 (Found: C, 77.01; H, 7.20; N, 3.85. C25H27NO3 requires C, 77.09; H, 6.99; N, 3.60%); nmax(CCl4)/cm21 2910, 2890, 2830, 1585, 1460, 1270, 1210; dH(200 MHz; CDCl3) 1.30–1.90 (12 H, m, Ad-H), 2.25 (1 H, br s, 19-H), 2.31 (1 H, br s, 19-H), 3.44 (3 H, s, 10-CH3), 3.88 (3 H, s, 3-OCH3), 6.53 (1 H, d, J4,2 2.3, 4-H), 6.72 (1 H, dd, J2,1 8.6 and J2,4 2.3, 2-H), 7.00 (1 H, br d, J5,6 8.2, 5-H), 7.17 (1 H, ddd, J7,8 7.7, J7,6 7.3 and J7,5 0.9, 7-H), 7.39 (1 H, ddd, J6,5 8.2, J6,7 7.3 and J6,8 1.5, 6-H), 8.07 (1 H, d, J1,2 8.6, 1-H) and 8.18 (1 H, dd, J8,7 7.7 and J8,6 1.5, 8-H); dC(50 MHz; CDCl3) 25.2 (d), 25.4 (d), 31.4 (t), 31.5 (t), 32.6 (d), 32.7 (d), 32.7 (2t), 33.2 (q), 35.9 (t), 55.3 (q), 86.8 (s), 97.8 (s), 98.3 (d), 104.5 (d), 111.7 (d), 114.1 (s), 120.2 (d), 121.5 (s), 127.7 (d), 128.8 (d), 129.0 (d), 140.1 (s), 141.3 (s) and 160.1 (s). 4-Methoxy-10-methyldispiro[acridane-9,39-[1,2]dioxetane- 49,20-adamantane] (4c).—Photooxygenation of the olefin 3c (42.0 mg, 117 mmol) in CDCl3 (3.0 cm3) for 20 min gave the dioxetane 4c as a yellow, amorphous powder (29.0 mg, 64%), Rf(light petroleum–diethyl ether 5 : 1) 0.55 (Found: C, 76.68; H, 6.92; N, 3.24.C25H27NO3 requires C, 77.09; H, 6.99; N, 3.60%); nmax(CCl4)/cm21 2910, 2890, 2830, 1475, 1455, 1440, 1335, 1240, 1085, 1015; dH(200 MHz; CDCl3) 1.10–2.10 (12 H, m, Ad-H), 2.26 (1 H, br s, 19-H), 2.38 (1 H, br s, 19-H), 3.64 (3 H, s, 10- CH3), 3.85 (3 H, s, 4-OCH3), 6.94 (1 H, dd, J3,2 7.9 and J3,1 1.4, 3-H), 7.06–7.16 (2 H, m, 5-H and 7-H), 7.13 (1 H, dd, J2,1 and J2,3 7.9, 2-H), 7.38 (1 H, m, 6-H), 7.82 (1 H, dd, J1,2 7.9 and J1,3 1.4, 1-H) and 8.08 (1 H, dd, J8,7 7.7 and J8,6 1.5, 8-H); dC(50 MHz; CDCl3) 25.5 (d), 25.8 (d), 31.7 (t), 31.8 (t), 33.0 (2d), 33.0 (2t), 36.2 (t), 39.2 (q), 56.2 (q), 87.4 (s), 97.5 (s), 112.4 (d), 113.4 (d), 120.1 (d), 120.2 (d), 121.3 (d), 123.0 (s), 126.3 (s), 127.4 (d), 128.9 (d), 130.8 (s), 143.1 (s) and 149.2 (s). 2-(tert-Butyldimethylsiloxy)-10-methyldispiro[acridane-9,39- [1,2]dioxetane-49,20-adamantane] (4g).—Photooxygenation of the olefin 3g (34.0 mg, 74.3 mmol) in CDCl3 (1.0 cm3) for 30 min gave the dioxetane 4g as a yellow, amorphous powder (20.0 mg, 55%), Rf(light petroleum–diethyl ether 5 : 1) 0.67 (Found: C, 73.62; H, 8.07; N, 2.73.C30H39NO3Si requires C, 73.58; H, 8.03; N, 2.86%); nmax(CDCl3)/cm21 2910, 2890, 2840, 1590, 1490, 1460, 1265, 1250, 835; dH(200 MHz; CDCl3) 0.16 (3 H, s, SiMe), 0.18 (3 H, s, SiMe), 0.98 (9 H, s, SiCMe3), 1.20–1.90 (12 H, m, Ad-H), 2.24 (1 H, br s, 19-H), 2.38 (1 H, br s, 19-H), 3.43 (3 H, s, 10-CH3), 6.89 (2 H, m, 3-H and 5-H), 6.99 (1 H, d, J4,3 8.0, 4- H), 7.15 (1 H, ddm, J7,8 7.5 and J7,6 7.3, 7-H), 7.40 (1 H, m, 6- H), 7.65 (1 H, d, J1,3 1.2, 1-H) and 8.15 (1 H, dm, J8,7 7.5, 8-H); dC(50 MHz; CDCl3) 24.4 (2q), 18.2 (s), 25.5 (d), 25.7 (3q), 25.8 (d), 31.7 (2t), 32.9 (2d), 32.9 (2t), 33.1 (q), 36.2 (t), 87.1 (s), 97.9 (s), 111.4 (d), 112.4 (d), 119.2 (d), 119.8 (d), 120.9 (d), 121.0 (s), 122.6 (s), 134.8 (s), 127.9 (d), 128.9 (d), 140.6 (s) and 152.3 (s). 3-(tert-Butyldimethylsiloxy)-10-methyldispiro[acridane-9,39- [1,2]dioxetane-49,20-adamantane] (4h).—Photooxygenation of the olefin 3h (12.0 mg, 26.2 mmol) in CDCl3 (0.7 cm3) for 30 min gave the dioxetane 4h as a yellow, amorphous powder (10.0 mg, 78%), Rf(light petroleum–diethyl ether 5 : 1) 0.70 (Found: C, 73.62; H, 7.75; N, 2.96.C30H39NO3Si requires C, 73.58; H, 8.03; N, 2.86%); nmax(CDCl3)/cm21 2930, 2860, 1620, 1530, 1510, 1310, 1290, 880; dH(200 MHz; CDCl3) 0.20 (3 H, s, SiMe), 0.22 (3 H, s, SiMe), 0.98 (9 H, s, SiCMe3), 1.10–1.90 (12 H, m, Ad- H), 2.19 (1 H, br s, 19-H), 2.31 (1 H, br s, 19-H), 3.42 (3 H, s, 10- CH3), 6.48 (1 H, d, J4,2 2.1, 4-H), 6.65 (1 H, dd, J2,1 8.3 and J2,4 2.1, 2-H), 7.02 (1 H, br d, J5,6 8.3, 5-H), 7.17 (1 H, ddm, J7,8 7.6 and J7,6 7.3, 7-H), 7.40 (1 H, ddd, J6,5 8.3, J6,7 7.3 and J6,8 1.3, 6- H), 7.98 (1 H, d, J1,2 8.3, 1-H) and 8.17 (1 H, dd, J8,7 7.6 and J8,6 1.3, 8-H); dC(50 MHz; CDCl3) 24.5 (q), 24.3 (q), 18.2 (s), 25.2 (d), 25.4 (d), 25.6 (3q), 31.4 (t), 31.6 (t), 32.6 (2d), 32.7 (2t), 33.1 (q), 35.9 (t), 88.6 (s), 98.0 (s), 103.8 (d), 111.7 (d), 112.0 (d), 120.2 (s), 120.2 (d), 121.5 (s), 126.6 (d), 127.8 (d), 128.8 (d), 140.1 (s), 141.9 (s) and 154.8 (s). 2-Acetoxy-10-methyldispiro[acridane-9,39-[1,2]dioxetane- 49,20-adamantane] (4j).—Photooxygenation of the olefin 3j (28.0 mg, 72.6 mmol) in CDCl3 (2.0 cm3) for 45 min gave the dioxetane 4j as a yellow, amorphous powder (12.0 mg, 40%), Rf(light petroleum–diethyl ether 5 : 1) 0.23 (Found: C, 74.62; H, 6.92; N, 3.24.C26H27NO4 requires C, 74.80; H, 6.52; N, 3.35%); nmax(CCl4)/cm21 2900, 2840, 1705 (CO), 1590, 1495, 1460, 1200; dH(200 MHz; CDCl3) 1.10–2.10 (12 H, m, Ad-H), 2.30 (2 H, br s, 19-H), 2.32 (3 H, s, COCH3), 3.46 (3 H, s, 10- CH3), 6.97–7.03 (2 H, m, 4-H and 5-H), 7.12–7.21 (2 H, m, 3-H and 7-H), 7.41 (1 H, ddd, J6,5 8.4, J6,7 7.1 and J6,8 1.3, 6-H), 7.90 (1 H, d, J1,3 2.7, 1-H) and 8.15 (1 H, dd, J8,7 8.7 and J8,6 1.3, 8- H); dC(50 MHz; CDCl3) 21.1 (q), 25.5 (d), 25.7 (d), 31.6 (t), 31.7 (t), 32.9 (2d), 32.9 (t), 33.0 (t), 33.3 (q), 36.1 (t), 86.9 (s), 97.9 (s), 111.7 (d), 112.3 (d), 120.5 (d), 120.9 (s), 121.0 (d), 122.2 (d), 122.6 (s), 128.0 (d), 129.2 (d), 138.2 (s), 140.2 (s), 144.4 (s) and 169.9 (s). 3-Acetoxy-10-methyldispiro[acridane-9,39-[1,2]dioxetane- 49,20-adamantane] (4k).—Photooxygenation of the olefin 3k (12.0 mg, 31.1 mmol) in CDCl3 (0.7 cm3) for 30 min gave the dioxetane 4k as a yellow, amorphous powder (5.00 mg, 39%), Rf(light petroleum–diethyl ether 5 : 1) 0.15 (Found: C, 74.40; H, 6.42; N, 2.94. C26H27NO4 requires C, 74.80; H, 6.52; N, 3.35%); nmax(CCl4)/cm21 2920, 2900, 2840, 1755 (CO), 1585, 1530, 1455, 1200, 1170, 905; dH(200 MHz; CDCl3) 1.20–2.00 (12 H, m, Ad- H), 2.23 (2 H, br s, 19-H), 2.35 (3 H, s, COCH3), 3.44 (3 H, s, 10- CH3), 6.75 (1 H, br s, 4-H), 6.90 (1 H, dm, J2,1 8.3, 2-H), 7.02 (1 H, br d, J5,6 8.3, 5-H), 7.19 (1 H, m, 7-H), 7.41 (1 H, m, 6-H), 8.16 (1 H, d, J1,2 8.3, 1-H) and 8.16 (1 H, m, 8-H); dC(50 MHz; CDCl3) 21.3 (q), 25.1 (d), 25.4 (d), 31.4 (2t), 32.6 (2d), 32.7 (2t), 33.2 (q), 35.9 (t), 86.7 (s), 97.7 (s), 105.2 (d), 111.7 (d), 113.3 (d), 119.0 (s), 120.6 (d), 124.2 (s), 127.8 (d), 128.9 (d), 129.0 (d), 139.8 (s), 141.1 (s), 151.1 (s) and 169.8 (s).Synthesis of the dioxetane decomposition products 5 The known N-methyl acridones 5a–c 23,24 were prepared according to the literature procedure 25 by methylation of the corresponding acridones.23 The hydroxy acridones 5d–f 24 were synthesized by ether cleavage of the methoxy acridones 5a–c in hydrobromic acid.The physical and spectral data of these compounds are consistent with those reported.23–25 General procedure for the silylation of the hydroxyacridones 5d–f. To a solution of the hydroxyacridone 5d–f (1.0 equiv.) and tert-butyldimethylchlorosilane (1.4 equiv.) in dry DMF (5–10 cm3) was added a solution of imidazole (2.0 equiv.) in dry DMF (2.5–5 cm3).After stirring at 40–50 8C for 4 h, more silane (0.7 equiv.) and imidazole (1.0 equiv.) were added and the stirring was continued for 20 h. The solution was poured into water (15 cm3), the precipitate was collected, dried over P2O5 at 20 8C and 10 Torr and purified by recrystallization from ethanol or by chromatography on silica gel. 2-(tert-Butyldimethylsiloxy)-10-methylacridone (5g).—By following the above procedure, from the hydroxyacridone 5d (900 mg, 4.00 mmol), tert-butyldimethylchlorosilane (1.23 g, 8.00 mmol) and imidazole (816 mg, 12.0 mmol) the siloxy acridone 5g was obtained as a yellow powder (750 mg, 55%), mp 109– 110 8C (from EtOH), Rf(light petroleum–ethyl acetate 1 : 1) 0.75 (Found: C, 71.01; H, 7.74; N, 3.87.C20H25NO2Si requires C, 70.76; H, 7.42; N, 4.13%); nmax(KBr)/cm21 2930, 2900, 2860, 2830, 1615 (CO), 1580, 1490, 1450, 1270, 1230, 910, 825, 745; lmax(CH3CN)/nm 251 (log e 4.64), 270 (4.51), 397 (3.88), 416 (3.95); dH[600 MHz; (CD3)2SO] 0.23 (6 H, s, SiMe2), 0.98 (9 H, s, SiCMe3), 3.92 (3 H, s, 10-CH3), 7.30 (1 H, ddd, J7,8 7.9, J7,6 6.6 and J7,5 1.2, 7-H), 7.39 (1 H, dd, J3,4 9.4 and J3,1 3.1, 3-H), 7.71 (1 H, d, J3,1 3.1, 1-H), 7.78–7.83 (2 H, m, 5-H and 7-H), 7.81 (1 H, d, J4,3 9.1, 4-H) and 8.31 (1 H, dd, J8,7 7.9 and J8,6 1.5, 8-H); dC[151 MHz; (CD3)2SO] 24.7 (2q), 17.9 (s), 25.5 (3q), 33.6 (q), 114.1 (d), 115.8 (d), 117.9 (d), 120.6 (s), 120.7 (d), 122.4 (s), 126.3 (d), 127.5 (d), 133.7 (d), 137.4 (s), 141.9 (s), 149.4 (s) and 175.8 (s). 3-(tert-Butyldimethylsiloxy)-10-methylacridone (5h).—By following the above procedure, from the hydroxyacridone 5e (4331462 J. Chem. Soc., Perkin Trans. 2, 1997 mg, 1.92 mmol), tert-butyldimethylchlorosilane (597 mg, 3.96 mmol) and imidazole (394 mg, 5.78 mmol) the siloxy acridone 5h was obtained as colourless needles (201 mg, 31%), mp 125.5– 126.5 8C (from EtOH), Rf(light petroleum–ethyl acetate 1 : 1) 0.30 (Found: C, 70.84; H, 7.88; N, 4.06.C20H25NO2Si requires C, 70.76; H, 7.42; N, 4.13%); nmax(KBr)/cm21 2930, 2900, 2830, 1615 (CO), 1580, 1450, 1330, 1280, 1210, 980, 860, 750; lmax(CH3CN)/nm 256 (log e 4.74), 268 (4.72), 277 (4.71), 372 (3.99), 388 (4.09); dH[200 MHz; (CD3)2SO] 0.30 (6 H, s, SiMe2), 1.00 (9 H, s, SiCMe3), 3.86 (3 H, s, 10-CH3), 6.87 (1 H, dd, J2,1 8.7 and J2,4 2.0, 2-H), 7.10 (1 H, d, J4,2 2.0, 4-H), 7.32 (1 H, ddd, J7,8 7.7, J7,6 5.1 and J7,5 2.8, 7-H), 7.80 (2 H, m, 5-H and 6-H), 8.26 (1 H, d, J1,2 8.7, 1-H) and 8.31 (1 H, dm, J8,7 7.7, 8-H); dC[50 MHz; (CD3)2SO] 24.5 (2q), 18.0 (s), 25.5 (3q), 33.7 (q), 105.2 (d), 114.9 (d), 115.9 (d), 116.7 (s), 121.0 (d), 121.6 (s), 126.4 (d), 128.8 (d), 133.6 (d), 142.4 (s), 144.1 (s), 160.2 (s) and 175.6 (s). 4-(tert-Butyldimethylsiloxy)-10-methylacridone (5i).—By following the above procedure, from the hydroxyacridone 5f (340 mg, 1.51 mmol), tert-butyldimethylchlorosilane (464 mg, 3.08 mmol) and imidazole (306 mg, 4.50 mmol) the siloxy acridone 5i was obtained as yellow needles (392 mg, 77%), mp 97–98 8C, Rf(light petroleum–ethyl acetate 2 : 1) 0.74 (Found: C, 70.41; H, 7.67; N, 4.06.C20H25NO2Si requires C, 70.76; H, 7.42; N, 4.13%); nmax(KBr)/cm21 2940, 2910, 2830, 1615 (CO), 1590, 1580, 1490, 1450, 1350, 1255, 1190, 915, 825, 750; lmax(CH3CN)/nm 259 (log e 4.59), 299 (3.65), 312 (3.69), 393 (3.90), 406 (3.89); dH[200 MHz; (CD3)2SO] 0.24 (6 H, s, SiMe2), 0.96 (9 H, s, SiCMe3), 3.97 (3 H, s, 10-CH3), 7.23 (1 H, dd, J2,1 and J2,3 7.7, 2-H), 7.26–7.36 (2 H, m, 3-H and 7-H), 7.74–7.82 (2 H, m, 5-H and 6-H), 7.92 (1 H, dd, J1,2 7.7 and J1,3 2.0, 1-H) and 8.23 (1 H, dm, J8,7 8.0, 8-H); dC[50 MHz; (CD3)2SO] 24.4 (2q), 18.2 (s), 25.7 (3q), 41.2 (q), 116.9 (d), 119.0 (d), 121.4 (d), 121.7 (s), 122.1 (d), 124.3 (d), 125.2 (s), 126.0 (d), 133.8 (s), 134.0 (d), 137.0 (s), 145.2 (s) and 176.9 (s). General procedure for the acetylation of the hydroxyacridones 5d–f.To a suspension of sodium hydride (60% dispersion in mineral oil, 2.0 equiv.) in dry DMF (5 cm3) was added the hydroxyacridone 5d–f (1.0 equiv.).The mixture was stirred for 30 min and then acetic anhydride (1.1–2.0 equiv.) was added. Stirring was continued for a further 30 min, then water (10 cm3) was added, the precipitate was collected, dried over P2O5 at 20 8C and 10 Torr and purified, if necessary, by chromatography on silica gel. Thereby, the impurities were removed by eluting with methylene chloride and the acridone was subsequently recovered by washing with ethyl acetate. 2-Acetoxy-10-methylacridone (5j).—By following the above procedure, from the hydroxyacridone 5d (355 mg, 1.58 mmol), sodium hydride (126 mg, 3.16 mmol) and acetic anhydride (300 ml, 3.17 mmol) the acetoxy acridone 5j was obtained as a yellow powder (311 mg, 74%), mp 202–203 8C (Found: C, 71.97; H, 4.70; N, 5.11. C16H13NO3 requires C, 71.90; H, 4.90; N, 5.24%); nmax(KBr)/cm21 2900, 2830, 1725 (CO), 1620 (CO), 1590, 1490, 1230, 745; lmax(CH3OH)/nm 247 (log e 4.48), 267 (4.52), 391 (4.00), 409 (4.05); dH[600 MHz; (CD3)2SO] 2.32 (3 H, s, COCH3), 3.96 (3 H, s, 10-CH3), 7.36 (1 H, ddd, J7,8 8.0, J7,6 5.6 and J7,5 2.3, 7-H), 7.63 (1 H, dd, J3,4 9.4 and J3,1 2.9, 3-H), 7.86 (2 H, m, 5-H and 6-H), 7.93 (1 H, d, J4,3 9.4, 4-H), 8.02 (1 H, d, J1,3 2.9, 1-H) and 8.34 (1 H, dm, J8,7 8.0, 8-H); dC[151 MHz; (CD3)2SO] 20.8 (q), 33.9 (q), 116.2 (d), 117.9 (d), 117.9 (d), 121.1 (s), 121.3 (d), 121.8 (s), 126.4 (d), 128.3 (d), 134.2 (d), 140.1 (s), 142.2 (s), 144.5 (s), 169.5 (s) and 175.8 (s). 3-Acetoxy-10-methylacridone (5k).—By following the above procedure, from the hydroxyacridone 5e (17.0 mg, 75.5 mmol), sodium hydride (6.00 mg, 150 mmol) and acetic anhydride (15.0 ml, 159 mmol) the acetoxy acridone 5k was obtained as a paleyellow powder (20.0 mg, 98%), mp 165–166 8C (Found: C, 71.61; H, 4.76; N, 5.10. C16H13NO3 requires C, 71.90; H, 4.90; N, 5.24%); nmax(KBr)/cm21 2900, 1735 (CO), 1620 (CO), 1585, 1455, 1205, 1180, 755; lmax(CH2Cl2)/nm 293 (log e 3.68), 376 (3.85), 394 (4.00); dH[200 MHz; (CD3)2SO] 2.35 (3 H, s, COCH3), 3.90 (3 H, s, 10-CH3), 7.13 (1 H, dd, J2,1 8.7 and J2,4 1.9, 2-H), 7.37 (1 H, ddd, J7,8 8.0, J7,6 5.0 and J7,5 2.9, 7-H), 7.66 (1 H, d, J4,2 1.9, 4-H), 7.87 (2 H, m, 5-H and 6-H), 8.35 (1 H, dm, J8,7 8.0, 8-H) and 8.37 (1 H, d, J1,2 8.7, 1-H); dC[50 MHz; (CD3)2SO] 20.9 (q), 33.9 (q), 109.0 (d), 116.0 (d), 116.2 (d), 119.4 (s), 121.5 (d), 121.6 (s), 126.4 (d), 128.3 (d), 134.1 (d), 142.4 (s), 143.4 (s), 155.0 (s), 168.9 (s) and 175.6 (s). 4-Acetoxy-10-methylacridone (5l).—By following the above procedure, from the hydroxyacridone 5f (150 mg, 0.666 mmol), sodium hydride (60.0 mg, 1.50 mmol) and acetic anhydride (150 ml, 1.59 mmol) the acetoxy acridone 5l was obtained as yellow needles (148 mg, 83%), mp 132–133 8C (Found: C, 71.69; H, 5.05; N, 5.31. C16H13NO3 requires C, 71.90; H, 4.90; N, 5.24%); nmax(KBr)/cm21 2900, 1750 (CO), 1620 (CO), 1585, 1490, 1180, 1160, 750; lmax(CH2Cl2)/nm 257 (log e 4.55), 292 (3.67), 305 (3.52), 383 (3.92), 400 (3.99); dH[600 MHz; (CD3)2SO] 2.45 (3 H, s, COCH3), 3.90 (3 H, s, 10-CH3), 7.35 (1 H, dd, J2,1 and J2,3 7.8, 2-H), 7.36 (1 H, ddd, J7,8 7.9, J7,6 7.0 and J7,5 0.9, 7-H), 7.58 (1 H, dd, J3,2 7.8 and J3,1 1.6, 3-H), 7.70 (1 H, br d, J5,6 8.6, 5-H), 7.85 (1 H, ddd, J6,5 8.6, J6,7 7.0 and J6,8 1.7, 6-H), 8.21 (1 H, dd, J1,2 7.8 and J1,3 1.6, 1-H) and 8.25 (1 H, dd, J8,7 7.9 and J8,6 1.7, 8-H); dC[50 MHz; (CD3)2SO] 20.9 (q), 40.2 (q), 116.9 (d), 121.6 (d), 121.8 (d), 121.8 (s), 124.2 (d), 124.8 (s), 126.0 (d), 129.1 (d), 134.3 (d), 137.4 (s), 139.2 (s), 144.6 (s), 169.0 (s) and 176.5 (s).Chemiluminescence measurements Determination of the activation parameters for the thermal decomposition of the dioxetanes 4a–c. A glass vial was charged with toluene (2.70–2.90 cm3), placed in the cell compartment of the Mitchell–Hastings photometer 20 and allowed to equilibrate thermally for ca. 5 min. An aliquot of dioxetane solution (ca. 1023 mol dm23 in toluene; 100–300 mm3) was introduced so that the total final volume was adjusted to 3.0 cm3 and the concentration was ca. 1025–1024 mol dm23. The emitted light intensity was continuously recorded. For the determination of activation parameters, runs at several temperatures (80–95 8C) were carried out by direct chemiluminescence measurements under isothermal conditions.The rate data were processed according to first-order kinetics and from the set of k values the activation parameters were calculated by Arrhenius and Eyring methods. The data are collected in Table 1. Determination of CIEEL quantum yields for the fluoride- and base-induced decomposition of the dioxetanes 4g,h,j,k. A glass vial was charged with the dioxetane solution (ca. 1027–1024 mol dm23 in methylene chloride, acetonitrile or methanol; 3.00 cm3) and placed in the cell compartment of the Mitchell–Hastings photometer.20 After 5 min of thermal equilibration at 25 8C, an appropriate amount of triggering agent [tetrabutylammonium fluoride (0.1 mol dm23 in methylene chloride or acetonitrile), tetrabutylammonium hydroxide (0.1 mol dm23 in acetonitrile or water) or sodium methanolate (0.1 mol dm23 in methanol)] was added by means of a syringe through the rubber septum into the above glass vial under rigorous exclusion of external light, with the photomultiplier open for immediate measurement of the light emission.The rate data were processed according to first-order kinetics and from the set of k values the CIEEL quantum yields were calculated as described.12 The results are collected in Table 2. Determination of the fluorescence quantum yields of the acridones 5g–l. To a sample of the acridones 5g–l (1027–1024 mol dm23 in methylene chloride, acetonitrile or methanol) was added a solution of triggering agent [tetrabutylammonium fluoride (0.1 mol dm23 in methylene chloride or acetonitrile), tetrabutylammonium hydroxide (0.1 mol dm23 in acetonitrile or water) or sodium methanolate (0.1 mol dm23 in methanol)].UV–VIS absorption as well as fluorescence spectra were recorded and from them the fluorescence quantum yields were calculated according to the literature procedure.26 QuinineJ. Chem. Soc., Perkin Trans. 2, 1997 1463 bisulfate (1.47 × 1026 mol dm23 in 1 M HClO4) was used as the standard (FFl 0.56) for calibration.Computational methods The calculations are based on the AM1 theory as implemented in the VAMP 5.0 software package 27 and run on a Silicon Graphics Indigo workstation. The excited-state calculations were performed by using the singles-plus-pair excitation con- figuration interaction (PECI) 28 approach with an active space of ten molecular orbitals (MO). Acknowledgements We thank the Deutsche Forschungsgemeinschaft (SFB 172 ‘Molekulare Mechanismen kanzerogener Primärveränderungen’) and the Fonds der Chemischen Industrie for generous financial support.References 1 J.-Y. Koo and G. B. Schuster, J. Am. Chem. Soc., 1977, 99, 6107; G. B. Schuster, Acc. Chem. Res., 1979, 12, 366. 2 W. Adam and O. Cueto, J. Am. Chem. Soc., 1979, 101, 6511; S. P. Schmidt and G. B. Schuster, J. Am. Chem. Soc., 1980, 102, 306. 3 K. A. Zaklika, A. L. Thayer and A. P. Schaap, J. Am. Chem. Soc., 1978, 100, 4916; K. A. Zaklika, T.Kissel, A. L. Thayer, P. A. Burns and A. P. Schaap, Photochem. Photobiol., 1979, 30, 35; A. P. Schaap and S. D. Gagnon, J. Am. Chem. Soc., 1982, 104, 3504. 4 J.-Y. Koo, S. P. Schmidt and G. B. Schuster, Proc. Natl. Acad. Sci. USA, 1978, 75, 30. 5 A. P. Schaap, R. S. Handley and B. P. Giri, Tetrahedron Lett., 1987, 28, 935; A. P. Schaap, T.-S. Chen, R. S. Handley, R. DeSilva and B. P. Giri, Tetrahedron Lett., 1987, 28, 1155; A. P. Schaap, M. D. Sandison and R. S. Handley, Tetrahedron Lett., 1987, 28, 1159. 6 I. Bronstein, B. Edwards and J. C. Voyta, J. Biolumin. Chemilumin., 1989, 4, 99; I. Bronstein, J. C. Voyta, G. H. G. Thorpe, L. J. Kricka and G. Armstrong, Clin. Chem., 1989, 35, 1441; G. H. G. Thorpe, I. Bronstein, L. J. Kricka, B. Edwards and J. C. Voyta, Clin. Chem., 1989, 35, 2319; I. Bronstein, J. C. Voyta and B. Edwards, Anal. Biochem., 1989, 180, 95; R. Tizard, R. L. Cate, K. L. Ramachandran, M. Wysk, J. C. Voyta, O. J. Murphy and I.Bronstein, Proc. Natl. Acad. Sci. USA, 1990, 87, 4514. 7 W. Adam and M. H. Schulz, Chem. Ber., 1992, 125, 2455; W. Adam, R. Fell and M. H. Schulz, Tetrahedron, 1993, 49, 2227; W. Adam and D. Reinhardt, J. Chem. Soc., Perkin Trans. 2, 1994, 1503. 8 M. Matsumoto, H. Suganuma, Y. Katao and H. Mutoh, J. Chem. Soc., Chem. Commun., 1995, 431; M. Matsumoto, H. Suganuma, M. Azami, N. Aoshima and H. Mutoh, Heterocycles, 1995, 41, 2419; M. Matsumoto, N. Watanabe, H. Kobayashi, H. Suganuma, J. Matsubara, Y. Kitano and H. Ikawa, Tetrahedron Lett., 1996, 37, 5939; M. Matsumoto, N. Watanabe, H. Kobayashi, M. Azami and H. Ikawa, Tetrahedron Lett., 1997, 38, 411. 9 (a) S. Beck and H. Köster, Anal. Chem., 1990, 62, 2258; (b) A. Mayer and S. Neuenhofer, Angew. Chem., 1994, 106, 1097; Angew. Chem., Int. Ed. Engl., 1994, 33, 1044; (c) Bioluminescence & Chemiluminescence, Current Status, ed. P. E. Stanley and L. J. Kricka, Wiley, Chichester, 1991. 10 F. McCapra, I. Beheshti, A. Burford, R. A. Hann and K. A. Zaklika, J. Chem. Soc., Chem. Commun., 1977, 944; F. McCapra and D. Watmore, Tetrahedron Lett., 1982, 23, 5225. 11 M. Siegmund, J. Bendig and K. Teuchner, Z. Chem., 1985, 25, 372; M. Siegmund, J. Bendig, M. von Löwis of Menar and J. Wilda, Monatsh. Chem., 1986, 117, 1113. 12 W. Adam, in Chemical and Biological Generation of Excited States, ed. W. Adam and G. Cilento, Academic Press, New York, 1982, ch. 4. 13 A. Trofimov, K. Mielke, R. F. Vasil’ev and W. Adam, Photochem. Photobiol., 1996, 63, 463. 14 G. B. Schuster, N. J. Turro, H.-C. Steinmetzer, A. P. Schaap, G. Faler, W. Adam and J. C. Liu, J. Am. Chem. Soc., 1975, 97, 7110; W. Adam and L. A. Arias Encarnación, Chem. Ber., 1982, 115, 2592; W. Adam, L. A. Arias Encarnación and K. Zinner, Chem. Ber., 1983, 116, 839. 15 T. Wilson, M. E. Landis, A. L. Baumstark and P. D. Bartlett, J. Am. Chem. Soc., 1973, 95, 4765. 16 F. McCapra, J. Chem. Soc., Chem. Commun., 1977, 946; T. Wilson, Photochem. Photobiol., 1995, 62, 601. 17 B. Edwards, A. Sparks, J. C. Voyta and I. Bronstein, J. Biolumin. Chemilumin., 1990, 5, 1. 18 F. McCapra, Tetrahedron Lett., 1993, 34, 6941; W. Adam, D. Reinhardt and C. R. Saha-Möller, Analyst, 1996, 121, 1527. 19 M. Kupfer and W. Abraham, J. Prakt. Chem., 1983, 325, 95; K.-P. Kronfeld and H.-J. Timpe, J. Prakt. Chem., 1988, 330, 571. 20 J. W. Hastings and G. Weber, J. Opt. Am. Soc., 1963, 53, 1410; G. W. Mitchell and J. W. Hastings, Anal. Biochem., 1971, 39, 243. 21 E. Bergmann, O. Blum-Bergmann and A. Freiherr von Christiani, Liebigs Ann. Chem., 1930, 483, 80; A. K. Colter, P. Plank, J. P. Bergsma, R. Lahti, A. A. Quesnel and A. G. Parsons, Can. J. Chem., 1984, 62, 1780. 22 R. A. Reed, J. Chem. Soc., 1944, 679. 23 K. Gleu and S. Nitzsche, J. Prakt. Chem., 1939, 153, 200. 24 G. K. Hughes, N. K. Matheson, A. T. Norman and E. Ritchie, Austr. J. Sci. Res., 1952, A5, 206. 25 I. B. Taraporewala and J. M. Kauffman, J. Pharm. Sci., 1990, 79, 173. 26 W. R. Dawson and M. W. Windsor, J. Phys. Chem., 1968, 72, 3251. 27 M. J. S. Dewar, E. G. Zoebisch, E. F. Healy and J. J. P. Stewart, J. Am. Chem. Soc., 1985, 107, 3902; G. Rauhut, A. Alex, J. Chandrasekhar, T. Steinke and T. Clark, VAMP 5.0, 1993, University of Erlangen-Nürnberg, Germany. 28 T. Clark, in Recent Experimental and Computational Advances in Molecular Spectroscopy, ed. R. Fausto, Kluwer Academic Publishers, Norwell, MA, 1993, p. 369. Paper 7/01189J Received 19th February 1997 Accepted 25th March 1997