摘要:
J. CHEM. SOC. PERKIN TRANS. I1 1984 Assignment of Configuration of Larger Bicyclo[n.l .O]Alkylamines. The Use of a Lanthanide Shift Reagent Elmar Vilsmaier," Claus M. Klein, and Rainer Adam Fachbereich Chemie, Universitat Kaiserslautern, Erwin- Schrodinger- Strasse, 0-6750Kaiserslautern, West Germany The detection of the endo- or exo-position for the amino-function in methylbicyclo[n.l .O]alkylmorpho- lines is accomplished by use of a lanthanide shift reagent. This method is particularly useful for larger [n.l.O]bicyclic systems because of the impossibility of establishing the configuration on the basis of the dynamics of the morpholino group. The differences in the chemical shifts caused by complexation of an endo- or an exo-amine are studied for the isomers of bicyclo[3.1 .O]hexylmorpholine.A method for the preparation of sterically pure methylbicyclo[n.l .O]alkylmorpholines is described. Until recently it was difficult to determine whether an amino- function in a disubstituted bicyclo[n.l .O]alkyl system (1) or (2) (X # H) was in the endo- or the exo-position. With the results of two X-ray analyses as a basis, Koch and his group attemp- ted to develop a method for distinguishing between the endo- isomer (1) and the exo-isomer (2) using I5Nn.m.r. spectro-scopy [As between (1) and (2) ca. 12 p.p.m.; I5Nn.m.r. signal of (1) at higher field]. We have now developed a very simple method for differentiating between the em-and endo-con- figurations (1) and (2) by observation of the dynamics of a nitrogen-heterocyclic function NR'RZ.Z-12'H N.m.r.spectraindicate that the dynamics of the heterocycle are more strongly hindered in (1) than in (2). In the simplest case this is detectable from the type of signal pattern of the heterocycle. Thus at room temperature morpholine, which we used most frequently, displays in the bicyclo[n.l .O]-hexane, -heptane, or -octane system an AA'XX' pattern in the exo-position (2) [n = 3-5; R'RZ = (CHz)zO(CHz)z]and an ABXY pattern in the endo-position (1) [n= 3-5, RIRZ= (CHz)20(CH2)z].z-10In these compounds (1) the AGS values for the dynamics of endo- morpholine amount to ca. 70-80 kJ mol-1.2-'o However, with a hydrogen atom as an exo-substituent (1; X = H) or with the bicyclo[n. 1 .O]-undecane, -dodecane, or -pentadecane sys- tem (1) (n = 8, 9, or 12) 3*53*11~12 the hindrance of the morph- oline dynamics decreases strongly.AG3 Values of only 50-60 kJ mo1-I result. Since for ring inversion of N-methylmorpho- line AGt is reported to be 48 kJ m01-',13 and the error limit for the determination of these quantities by the n.m.r. method is known to be in the range of 31-2 kJ mol-', these values are no longer sufficient to distinguish between (1) and (2). For X = H this implies no restriction for the assignment of configuration; in this case (1) and (2) have quite different 3JHH In the case of the larger ring coupling con~tants.'~-'~ systems, however, the application of a lanthanide shift reagent might be expected to allow the definite establishment of the configuration.In order to obtain exclusive complexation of the morpholine, we have studied this problem using methyl- substituted morpholinobicyclo[n. 1 .O]alkanes (6). Eu(fod)3 (3) 18-" was selected as the shift reagent. The different effects from complexation of an endo- or an exo-morpholine were investigated with the isomeric amines (11) and (12). A trans-bicyclic methyl derivative (9) was also included in these experi- ments, since it is expected to allow the study of the influence on syn- and anti-cyclopropane hydrogen atoms by the Eu- (fod)3-morpholine complex. Results and Discussion Synthesis of Methylbicyclo[n.1.O]alkylniorpholines (6) and (9).-In the field of middle-large ring systems, both cis- and R'R~N~X XXNR'R2 C F3C F2CF2, trans-morpholino(succinimido)bicyclo[n.1.O]alkanes (4) and (7) are accessible with high stereoselectivity from enamino- sulphonium ~alts.~*~~ Consequently (4) and (7) are suitable starting materials for synthesizing further [n.1 .O]bicyclic compounds.8*11-12*22As shown for the bicyclo[4.1 .O]heptane system, an alkyl substituent is introduced into the bicyclic system by reacting a methoxy-morpholino-derivative(5a) with Grignard reagents.' Therefore we investigated the prepar- ation of the methoxy-compounds (5) and (8) from (4) and (7). This is achieved by heating (4b-d) or (7d) in methanol- methoxide causing substitution of the succinimide by a methoxy-group. The addition of methoxide should avoid exo-endo isomerization catalysed by protons; see e.g.ref. 2. The reaction of (5) and (8), respectively, with methylmag- nesium iodide leads to the expected methylbicyclo[n.l .O]alkyl- morpholines (6) and (9). The compounds isolated from these reactions proved to be isomerically pure. Starting from the cis-succinimido-compound (4), the cis-derivatives (5) and (6) are obtained ;similarly the trans-succinimido-compound(7d) leads to trans-derivatives (8d) and (9d). The cis-trans con-figuration of the bicyclic compounds is indicated by the I3C n.m.r. data (Table 3). The cis-[n.l .O]bicyclic compounds (5) and (6) display a plane of symmetry. Therefore the n + 3 carbon atoms of a cis-[n.l.O]bicycle give either (42) + 2 signals (n = even) or (n + 1)/2 + 2 signals (n = odd).Consequently five signals are seen for (5b) and (6b), six signals for (5c) and (6c), and seven signals for (5d) and (6d); in every case the cyclopropane ring gives rise to one singlet and one doublet. On the other hand, the chirality of the trans-bicyclic derivatives produces for (8d) and (9d) three I3Cn.m.r. signals (2 doublets and 1 singlet) for the cyclopropane. The nine sig- (4) (5) CH3MgHal CH 30H __c (7) a; n= 4 b;n=5 c;n=8 d ;n= 9 CH3Mg Hal 1 nals expected for the nonamethylene bridge are not totally resolved because of partial superposition. In the 'H n.m.r. spectra there are distinct differences between the cis- and trans-derivatives especially in the region of the cyclopropane protons (Table 1).In (5b) and (6b) morph- oline appears in the 'H n.m.r. spectrum at room temperature as an ABXY signal, which coalesces upon warming to 60-70 "C. From the known approximation formula,23 a AGZ valueof 68.7-69 kJmol-' results for the topomerization of the HAHBand HxHymethylene hydrogen atoms, respectively. This establishes the endo-configuration of the morpholine in (5b) and (6b). In (5c and d) and (6c and d) the ABXY pattern becomes visible only at lower temperatures (Table 1); the corresponding J. CHEM. SOC. PERKlN TRANS. I1 1984 AGt values vary from 48.9 to 56.6 kJ mol-'. This order of magnitude for AG* is expected for an endo-morpholine in the bicyclo[8. 1 .O]undecane and bicyclo[9.1 .Oldodecane systems [e.g. AGt/kJ mol-': (4c) 54.9, 55.9 (X-ray structural analy- sis,); (4d) 58.9, 60.3 This is close to the energy required for the normal ring inversion of morpholine and therefore a definitive assignment of morpholine to the endo-position in (5c and d) and (6c and d) is not possible from a study of the dynamics.In the truns-derivatives (8d) and (9d) the low- temperature 'H n.m.r. spectra show complex signal systems because of chirality; the AGZ values for the morpholine dy- namics were not determined. Lanthanide-induced Shift (LIS) Experiments with Methyl- bicyclu[n.l .O]uZkylmorpholines (6) and (9).-Addition of 0.25, 0.5,0.75, and 1 mol. equiv. Eu(fod), (3) to a solution of the methylbicyclo[n. 1 .O]alkylmorpholines (6) in CDCI, leads to a large downfield shift of the morpholino signals.In an equi- molar mixture of (6b-d) and (3), the OCH2signals are shifted to 6 15-18 and the NCHzsignals appear in the region 6 8.5- 9.5. This is in contrast to unsubstituted morpholine, for which the NCHz signals are found at lower field than the OCHz resonances in the presence of trisdipivaloylmethanato-europium But these differences may be due to steric effects, which have a large influence on the complexation properties of amines [chemical shift of the a-methylene group in a 1 : 1 complex with (10): piperidine 6 38.20; 25 N-methyl-piperidine: 6 16.0 p.~.m.~~). For the establishment of the configuration of (6), the be-haviour of the signals of the bicyclic system is important. The cyclopropane signal is not strongly affected by addition of Eu(fodh (3).This signal with its characteristic splitting is ob- servable for (6b and c) in all mixtures with (3); for (6d) it is recognized clearly only in the mixture with 0.25 and 0.5 equiv. of (3). In the mixture with 0.5 equiv. of (3) this signal is shifted by 1.2-1.1 6units uniformly for (6b, c, and d) (Table 2). On the other hand, a strong influence on four hydrogen atoms of the bicyclic compound is observed by adding (3) to (6b and c) or (a).With 1 equiv. Eu(fodh they show a signal between 6 3.75 and 4.85. These four hydrogen atoms, most probably one hydrogen of each of the two by two methylene groups next to cyclopropane, should be on the syn-side of the carbon ring with respect to morpholine.A slight shift of the cyclopropane hydrogen signals on the one hand and large shift of signals of the carbocyclic frame- work on the other allow the establishment of the endo-morpholino configuration for (6b-d). In the case of (6b) the correctness of this assignment is confirmed by the observation of the morpholino dynamics. In order to obtain information about the influence of the morph~line-Eu(fod)~ complex on syn- or anti-cyclopropane hydrogen atoms, we have studied the 'H n.m.r. spectra of mixtures of (3) and the trans-compound (9d). In a 1 : 1 mix-ture of (3) and (9d), signals representing four hydrogen atoms are found between 6 4 and 5. It is to be expected that one of these signals corresponds to the anti-hydrogen atom on the cyclopropane ring.But it was not possible to trace the shift of the two different bridge head hydrogen atoms upon step- wise addition of Eu(fod),. Therefore (9d) is not suited to studying the shift effect of E~(fod)~ complexed to an exo-morpholino moiety. LIS Experiments with the Bicyclo[3.1 .O]hexylmorpholine Isomers (1 1) and (1 2).-The different effects of Eu(fod), complexing an endo- or an exo-morpholine are demonstrated with the bicyclo[3.1 .O]hexylmorpholines (1 1) and (12). As shown earlier, (1 1) and (12) are easily accessible from chloro- J. CHEM. SOC. PERKIN TRANS. 11 1984 25 Table 1. lH N.m.r. data (200 MHz; CDzC12; Me4Si) and AGS values for morpholinobicyclo[n.l.O]alkanes (3,(6), (S), and (9) Chemical shift (6) Characteristic coupling , NCHZ OCHz constants (Hz)* AGZ "1 T/"C HA HB Hx HY Other signals JAB JXY JBX T,'/"C kJ mol-' 20 2.59 3.09 3.57 3.87 3.3 (s, 3 H), 1.0-2.2 (m, 11.9 12.4 11.5 70 68.9 * 12 H) 65 69.0' -60 2.82 2.92 3.41 3.71 3.4 (s, 3 H), 1.15-1.9 (m, 11.5 10.4 10.5 -25 51.4 16 H),0.9-1.1 (m, 2 H) -18f 51.5 * -40 2.69 2.95 3.47 3.73 3.4 (s, 3 H), 1.15-1.9 (m, 11.6 10.4 11.3 5' 56.6 18 H), 0.95-1.15 (m, 2 H) 2f 56.0 20 2.16 2.58 3.51 3.74 1.6-1.9 (m, 4 H), 1.0-1.5 (m, 10.8 9.7 60 68.8 6 H), 0.9 (s, 3 H),0.44.6 67 68.7 (m, 2 H) -80 2.56 3.47 3.72 1.2-1.9 (m, 16 H),1.0 (s, 3 H), h 10.7 h -33 48.9f (mc) 0.4-0.5 (m, 2 H)-60 2.40 2.59 3.51 3.72 1.2-1.7 (m, 18 H),1.0(s, 3 H), 11.2 10.9 11.0 -8' 54.4 0.45-0.6 (m, 2 H) -8' 54.2 20 2.85 3.60 3.4 (s, 3 H),1.25-2.0 (m, i i 18 H), 0.5-1.25 (m, 2 H) 20 2.54 ' 3.59 1.2-1.9 (m, 16 H),1.0 (s, 3 H), i i 0.65-0.95 (m, 2 H),0.34.45 (m, 2 H) From the spectrum at 20 "C.Further coupling constants: JAX, JAY cu. 0.2 Hz, Jay cu. 2-3 Hz. Coalescence temperature; (5b) and (6b) in C2D2CI4. Calculated from ref. 23, limits of error fl-2 kJ mol-'. AB System. No separation of the signals. Not detectable. Typical morpholino AA'XX' pattern. Chirality gives a complex spectrum at low temperatures. Table 2. 'H N.m.r. data (200 MHz; CDC13; Me4Si; 20 "C) for mixtures of Eu(fodh (3) and morpholinobicyclo[n.l.O]alkanes(6),(ll), and (12) Cyclopropane -MethylEquivalents 1 H (t) groupCompds. Eu(fod)3(3) 2H 6-H (3 H, s) (CH2), moiety in the presence of 1 equiv. Eu(fodX (6b) 0 0.66 0.99 2.25-2.55 (m,2 H)," 2.6-3.05 (m, 4 H), 3.75-3.9 (m, 2 H),0.25 1.29 1.69 4.6-4.85 (m,2 H)0.5 1.76 2.20 0.75 2.19 2.66 1 2.32 2.81 (W 0 0.43 1.03 2.05-2.2 (m,4 H),"2.45-2.8 (m, 8 H),4.25-4.4(m, 4 H)0.25 1.09 1.74 0.5 1.63 2.34 0.75 1.83 2.56 1 2.11 2.86 (64 0 0.50 1 .00 1.95-2.83 (m,14 H): 4.14-4.36(m, 2 H), 4.36-4.60 (m, 2 H)0.25 1.17 1.72 0.5 1.70 2.32 0.75 b 2.75 1 b 3.05 (1 1) 0 1.33 1.53 3.52-3.73 (m, 3 H),4.63-4.80(m, 2 H),5.57-5.82 (m, 1 H)0.25 2.33 3.32 0.5 2.87 4.39 0.75 3.16 4.86 1 3.35 5.22 (12) 0 I .33 1.40 2.33-2.60 (m, 2 H), 2.85-3.40 (m, 4 H)0.25 2.64 2.85 0.5 3.62 3.86 0.75 4.25 4.52 1 4.75 5.06 a Superposition with the cyclopropane signal ;the resulting integral indicates the presence of two additional hydrogen atoms.The position of the cyclopropane signal cannot be assigned clearly because of other similar adjacent and overlapping signal systems. morpholinocyclohexene and LiA1H4 followed by separation group. In the 1 : 1 complex of (3) with (1 1) three hydrogen of the isomers by a buffer solution. Addition of 0.25, 0.5, atoms show resonances at lower field (6 4.7,5.7); in (12) a 0.75, and 1 mol. equiv. Eu(fodX (3) causes a smaller shift for maximal shifting up to A6 3.4 of the (CH,), signals is observed the bridgehead hydrogen atoms in (11) and a stronger shift (Table 2). The 'H n.m.r. spectra of the carbon ring in (11) for the same protons in (12) [As for the 1 : 1 mixture: (1 1) and (12), respectively without and with 0.5 equiv.of E~(fod)~, 2.02; (12) 3.421. Furthermore, there is a strong and character- are shown in the Figure. Within the limit of error the morph- istic difference for the hydrogen atoms of the trimethylene olino signals and the signal for 6-H in (11) and (12) are influenced equally by Eu(fod), (3) in the 1 : 1 complex [l : 1 complexes: NCHz (11) 6 10.5, (12) 6 10.3; OCH2(11) 6 21.6, (12) 6 20.4; 6-H (11) 6 3.69, (12) 6 3.663. LIS experiments with (11) and (12) confirm the correct assignment of the enda-morpholino configuration in (6b-d) by means of Eu(fod), (3). At the same time they demonstrate the characteristic rules for differentiation of an endo- from an em-morpholine in a bicyclo[n.1.O]alkane using Eu(fod), (3). I'? (12) (13) J J. CHEM. SOC. PERKIN TRANS. 11 1984 In the bicyclic systems studied so far, complexation could take place only between the Eu(fod), (3) and the morpholino- moiety. This turned out to be an essential prerequisite for establishing the configuration by this method. Though a cyano-function displays only little tendency towards complexation 25 for (3) with respect to an ether or an amino-group, the con- figuration of (13) cannot be established by addition of Eu(fod),. Three signals, situated very close to each other, are shifted downfield in the presence of Eu(fod)3. With 1 equiv. (3) they appear between 6 4 and 5, corresponding to six hydrogen atoms.In contrast to (6d), two more hydrogen atoms are influenced by the Eu(fod),, most probably the bridgehead hydrogen atoms. In this case their subsequent shift cannot be observed because of superposition with other signals. Al- together there is a change of the complexation properties between E~(fod)~ and the morpholino-moiety caused by the cyano-group which prohibits information about the con-figuration of (13) from being gained. A similar state of affairs was observed for the methoxy-morpholino-compound (5d). Therefore the establishment of configuration by means of E~(fod)~becomes difficult with [n.1.O]bicyclic systems which contain another substituent with complexing ability for E~(fod)~(3) in addition to the morpholino-group.As shown elsewhere,26 for this type of compound assignment of the con- figuration is possible by replacing the morpholino-group with a hexahydroazepine moiety, followed by a study of the dynam- ic properties of the latter species. I I1 I I I 1 5 4 3 2 6 2 1 Figure 1. 'H N.m.r. signals of the carbocyclic systems of (11) and (12) (b) without and (a) with 0.5 equiv. E~(fod)~ (200 MHz; CDCb; Me&; 20 "C) J. CHEM. SOC. PERKIN TRANS. II 1984 Table 3. ''C Chemical shifts (50.28 MHz; CDC13; Me,Si) of the morpholinobicyclo[n.l.O]alkanes (9,(6), (8), and (9)Chemical shift 6 ~~ ~~ Morpholine a 67.7, 50.1 67.8, 50.4 67.7, 50.1 67.6, 49.8 67.6, 50.3 67.7, 49.9 67.8, 49.9 67.6, 49.4 r Cyclopropane 86.5 (s), 30.6 (d) 80.2 (s), 29.1 (d) 82.9 (s), 29.8 (d) 47.8 (s), 31.0 (d) 41.6 (s), 29.1 (d) 44.2 (s), 30.0 (d) 84.5 (s), 22.5 (d), 32.9 (d) 46.2 (s), 34.7 (d), 32.0 (d) a All triplets.Superposition of 2 or more signals. Experimental M.p.s and b.p.s are uncorrected. M.p.s were measured with a Mettler FP 5 apparatus. 'H and n.m.r. spectra were recorded with a Bruker WP 200 spectrometer and chemical shifts are reported in 6 units from internal tetramethylsilane. The reactions of the aminobicycloalkane derivatives with the LIS experiments were carried out under nitrogen to exclude moisture. Mass spectra were measured at 70 eV with a Varian MAT 31 1 instrument. Microanalyses were performed with a Perkin-Elmer 240 elemental analyser.General Procedure fur the Preparation of Aminomethoxy-bicycZo[n. 1.O]alkanes (5) and (8).-The morpholinosuccinimi-dobicyclo[n. 1 .O]alkanes (4) and (7) were added to metallic sodium (0.24 g, 10 mmol) and dry methanol (20 ml) [(4b) 2.82 g; (4c) 3.34 g; (4d),3 (7d) 3.48 g; each 10 mmol]. After reflux- ing for 12 h (4b-d) and 3 days (7d), the methanol was evap- orated and the residue extracted with pentane (3 x 30 ml). Re- moving the solvent from the pentane extracts in vacuo gave colourless crystals of (5b-d) and (8d). 8-exo-Methoxy-8- morpholino-cis-bicyclo[5.1.O]octane (5b) (1.7 g, 76%) had m.p. 51.6 "C (Found: C, 69.0; H, 10.15; N, 6.1. C13H23N02 requires C, 69.3; H, 10.3; N, 6.2%); m/z 225 (M+, 12%).11 -exo-Methoxy- 1 1 -morphoZino-cis-bicycZo[8.1 .O]undecane (5c). (1.94 g, 72%) had m.p. 44 "C (Found: C, 71.5; H, 10.75; N, 5.0.C16H29N02requires C, 71.85; H, 10.95; N, 5.25%); m/z 267 (M+, 10%). 12-exo-Methoxy-12-morpholino-cis-bicyclo-[9.1.0]dodecane (5d) (2.46 g, 87%) had m.p. 53 "C (Found: C, 72.6; H, 11.2; N, 4.9. C17H31N02 requires C, 72.55; H, 11.1 ; N, 5.0%); m/z 281 (M+, 18%). 12-Methoxy-12-rnorphoZino-trans-bicycZo[9.1.0]dodecane(8d) (1.13 g, 60%) had m.p. 90 "C (Found: C, 72.3; H, 11.0; N, 4.8. CI7HJ1NO2 requires C, 72.55; H, 11.1; N, 5.0%); m/z 281 (M+, 10%). N-(MethylbicycZo[n.l .O]alkyl)rnorphoZines (6) and (9).-According to a published7 procedure a mixture of methyl- magnesium iodide in diethyl ether (0.2h1, 35 ml, 7 mmol) and the methoxymorpholinobicyclo[n.1 .O]alkanes (5) and (8) [(5b) 1.13 g; (5c) 1.34 g; (5d) and (8d) 1.41 g; each 5 mmol] was refluxed for 12 h.Work-up by addition of water (40 ml), extraction with pentane (3.x 30 ml), drying the pentane solution (Na2S04) and removing the pentane gave (6) and (9). Compounds (6b-d) form crystals, which may be recrystal-lized from acetonitrile. Compound (9d), an oil, was distilled in a Kugelrohr apparatus. N-(8-exo-MethyZ-cis-bicyclo[5.1.O]-octy1)morphoZine (6b) (0.79 g, 76%) had m.p. 71 "C (Found: C, 74.5; H, 10.8; N, 6.5. C13H2,N0 requires C, 74.6; H, 11.2; N, 6.7%) ; m/z 209 (M+, 23%). N-(1 1-exo-Methyl-cis-bicycZu-[8.1.O]undecyl)rnorpholine (6c)(1.05 g, 84%) had m.p. 86 "C (Found: C, 76.1 ;H, 11.3;N, 5.4.C,,H,,NO requires C, 76.45; H, 11.65; N, 5.55%); m/z 251 (M+,11%). N-(12-exo-Methyl- CarbocycleA Polymethylene bridge 32.9, 29.6, 25.8 28.5, 26.7, 22.3, 20.6 26.6, 25.9, 23.2, 22.9, 22.2 32.9, 29.9, 24.4 29.0, 26.8, 22.5, 20.2 26.7, 26.4, 23.3, 22.9, 21.6 27.5, 27.3, 26.5, 26.3,b 26.1, 25.9, 22.8 26.9,b 26.4, 26.2, 25.3, 23.3 cis-bicycZo[9.1 .O]dodecyl)morpholine (6d) (1.20 g, 91%) had m.p. 90 "C (Found: C, 76.9; H, 1155; N, 5.2. C17H31N0 requires C, 76.9; H, 11.75; N, 5.3%); m/z 265 (M+, 9%). N-(12-exo- Methyl-trans-bicyclo[9.1.O]dodecyl)rnorpholine (9d) (1.O g, 75%) had b.p. 115-118 "C at 0.05 Torr (Found: C, 76.6; H, 11.65; N, 5.1. C17H31N0 requires C, 76.9; H, 11.75; N, 5.3%); m/z 265 (M+, 12%). LIS Experiments with Bicyclo[n.1.O]alkylmorpholines (9,(6), (9), and (1 1)-( 13).-Eu(fod), (3) (1 -06 g, 1.02 mmol) was dissolved in a few ml of dry CDC13; the solution made up to 10 ml with CDC13 containing 1.02 x mmol substrate per 0.1 ml solvent. From the bicyclo[n. 1 .O]alkylmorpholines (3,(6), (9), and (11)-(13) solutions were also prepared in dry CDC13; 0.1 ml of these solutions contained 4.08 x mmol (3,(6), (9), and (11)-(13) [amounts for 1 ml solution: (6b) 85.4 mg; (6c)102.6 mg; (6d), (9d) 108.3 mg; (ll), (12) 68.3 mg; (5d) 114.8 mg, (13) 112.8 mg; each 0.408 mmol]. With exclusion of moisture under nitrogen the E~(fod)~ solution (O,O.l, 0.2,0.3, and 0.4 ml) and CDC13 (0.4, 0.3, 0.2, 0.1, and 0 ml) was added to the bicycloalkylmorpholine solutions (0.1 ml). 'H N.m.r.spectra were run for each of the mixtures (0.5 ml). Acknowledgements We thank the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for support. We also thank Professor W. D. Sheldrick, Kaiserslautern, for checking our English. References 1 R. C. Haltiwanger, J. M. Burns, G. C. Crockett, and T. H. Koch, J. Am. Chem. SOC.,1978,100, 51 10. 2 E. Vilsmaier and W. Troger, Angew. Chem., Int. Ed. Engl., 1979, 18, 798; E. Vilsmaier, W. Troger, and G. Haag, Chem. Ber., 1981, 114, 67. 3 E. Vilsmaier and C. M. Klein, Angew. Chem., Int. Ed. Engl., 1979, 18, 800; E. Vilsmaier, C. M.Klein, D. Dausmann, and G. Maas, Chem. Ber., 1982,115, 1209. 4 E. Vilsmaier and W. Troger, Synthesis, 1980, 463; 1981, 207, 721; Chem. Ber., 1982, 115, 1644.5 E. Vilsmaier and L. Scheiber, Synthesis, 1980, 465. 6 E. Vilsmaier, W. Troger, and M. Gewehr, Angew. Chem., Int. Ed. Engl., 1981, 20, 273. 7 E. Vilsmaier and C. M. Klein, Synthesis, 1981, 206. 8 E. Vilsmaier, C. M. Klein, W. 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ISSN:1472-779X
DOI:10.1039/P29840000023
出版商:RSC
年代:1984
数据来源: RSC