摘要:
A reactivity study of [q6-(tert-butylsulfonyl)benzene] -rn tricarbonylchromium(0) IInW 7T Susan E. Gibson (n6e Thomas),*,' Nathalie Guillo," Andrew J. P. Whiteb and David J. Williamsb a Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London S W7 2A Y, UK Chemical Crystallography Laboratory, Imperial College of Science, Technology and Medicine, South Kensington, London S W7 2A Y, UK Addition of nucleophiles [LiC(Me),CN, LiCHS(CH,),S, BrMgCH,CH=CH,, LiCH,CO,Bur] to tricarbonyl[$-( tert-butylsulfonyl)benzene] chromium(0) 4 followed by iodine oxidation gives moderate to excellent yields (43-97%) of the novel para-disubstituted arenes 5a-d. Treatment of complex 4 with 1.0 or 2.1 equiv. of butyllithium followed by an electrophilic quench (ClSiMe,, ClCO,Me, ClPPh,, MeSSMe) gives the ortho- and di-ortho-substituted products 6a-b and 7a4, respectively in moderate to excellent yield (40-90%).Addition of complex 4 to 1.0,2.0 and 3.5 equiv. of LiTMP (LiTMP = lithium 2,2,6,6-tetramethylpiperidide)followed by a ClSiMe, quench gives the ortho silylated product 6a, the ortho, meta disilylated product 9 and, surprisingly, the ortho, ortho, para trisilylated product 10 respectively. The structure of [q6-l-( tert-butylsulfonyl)-2,5-bis(trimethylsilyl)benzene]tricarbonyl-chromium(o) 9 has been established by an X-ray crystallographic analysis. The fundamental chemistry of (q6-arene)tricarbonylchro-mium(o) complexes and its application to various areas of organic chemistry continues to attract considerable attention.For example, seminal studies on chiral base mediated asymmetric functionalisation of (q6-arene)tricarbonylchro-mium(0) complexes are currently being conducted by several groups,' g2 whilst recent applications to topical areas of organic synthesis include an innovative synthesis of ( -)-steganone, in which the key step is a stereoselective cross-coupling between an enantiopure chromium complex and an arylboronic acid,3 and the application of an enantioselective (q6-arene)tricarbonyl- chromium(o) based catalyst to the synthesis of the 10-membered macrolide ph~rcantholide.~ Earlier studies of the chemistry of (q6-arene)tricarbonylchro-mium(o) complexes defined their reactivity towards nucleo- philes5 and achiral bases.6 In general, these studies focused on complexes bearing donor substituents (e.g.OR, NR,, alkyl). Recently we reported the synthesis of the first sulfonyl-substituted (q6-arene)tricarbonylchromium(o) complexes.' In view of the strong electron withdrawing properties of the sulfonyl functional group, which we anticipated would lead to reactivity that was complementary to that of the majority of complexes examined to date, we initiated a study of the reactions of this type of complex. The results of our study, which not only defined the reactivity of sulfonyl-substituted (q6-arene)tricarbonylchromium(o) complexes with respect to nucleophiles and bases, but also led to the unprecedented production of a trisubstituted product from a deprotonation-electrophilic quench sequence, are described herein. Results and discussion [q 6-( tert- Bu t ylsulfon yl)benzene] t ricarbonylc hromium(o) 4 was selected as the substrate for our investigations, as it was envisaged that the relatively acidic methyl hydrogens of the previously synthesised tricarbonyl[q6-(methylsulfony1)ben-zene]chromium(o) would be incompatible with the proposed nucleophilic addition and deprotonation studies.Thus thio- phenol 1 was reacted with tert-butyl alcohol in the presence of perchloric acid and acetic anhydride in acetic acid (Scheme l), using a modified literature procedure,8 to give (tert- butylsulfany1)benzene2 (93%). Oxidation of 2 with potassium hydrogen persulfate, using a modified literature procedure, lo provided (tert-butylsulfony1)benzene 3 (90%) which was subsequently converted into its tricarbonylchromium(o) complex 4 by heating with hexacarbonylchromium(0) in 1,4-dioxane under reflux for 4 days. Column chromatography and crystallisation gave the novel complex 4 as yellow crystals in acceptable yield (68%).Nucleophilic addition studies It is firmly established that nucleophilic addition to (q6-arene)tricarbonylchromium(o) complexes generates anionic cyclohexadienyl complexes that are readily oxidised to uncomplexed arenes, thus effecting nucleophilic aromatic substitution of the arene ring. The regioselectivity of this process has been the subject of numerous studies,' the results of which may be summarised as follows. Nucleophilic addition to arene complexes bearing NMe,, OMe and F substituents is strongly directed to the meta position; only small amounts of ortho-substituted products (0-10%) are ever formed and para- substitution is not observed at all.The selectivity is less pronounced for attack on arene complexes bearing Me or C1 substituents. meta-Substitution is always significant but ortho- substitution may account for 50-70% of the product mixture; againpara-substitution is insignificant. Significantpara-substitu-tion has only been observed to date in the following cases: (i) nucleophilic addition of a cyano stabilised anion to tricarbonyl(q6-C6Hs~~3)chromium(o)which gave a 33% combined yield of para- and meta-substituted products in a ratio of 7 :3, (ii) nucleophilic addition to complexes substituted with very sterically demanding alkyl groups as exemplified by the addition of LiC(Me),CN to tricarbonyl[q6-C6H,CH-(Bu'),]chromium(~) which gave a 63% yield of the para- substituted product (less bulky alkyl groups give predominantly meta attack), and (iii) nucleophilic addition of LiC(Me),CN to tricarbonyl(q6-C6HsSiMe,)chromium(o) which gave a 65% combined yield of para- and meta-substituted products in a ratio of 98 :2.J. Chem. Soc., Perkin Trans. I, 1996 2575 SH SBu' S(0hBu' S(O)~BU'I I I I 1 4 Addition of LiC(Me),CN to the tert-butylsulfonyl-substi-tuted complex 4 was examined by reacting 1.2 equiv. of LiC(Me),CN with complex 4 in THF in the presence of 1,3-dimethy1-3,4,5,6-tetrahydropyrimidin-2(1 H)-one (DM PU) at 0 "C for 1.5 h and then quenching with iodine at -78 "C and stirring for a day at room temperature. Work-up, column S(0)2Bu'I iv-@ R - 4 5a R = C(Me)2CN 83% 5b R = CHS(CH2)3S 67% 5~ R = CH2CHZCH2 43% 5d R =CH~CO~BU' 97% S(0kBu'I 7(0)2Bu' 4 6a R=SiMe3 80% 6b R=COzMe 74% S(0)2Bu'I @crtc0)3 4 7a R=SiMe3 87% 7b R=PPh2 90% 7c R=SMe 69% 7d R=CO2Me 40% S(O)~BU'I 4 8 Scheme 1 Reagents: i, Bu'OH, AcOH, HC104, Ac,O, 93%;ii, KHSO,, 90%;iii, Cr(CO),, 68%; iv, RLi or RMgBr, then I,; v, BuLi (1 equiv.), then RCI; vi, BuLi (2.1 equiv.), then RCl or RSMe; vii, BuLi (I equiv.), then Me,SiCI, then BuLi (I equiv.), then PPh,Cl, 48% co oc Fig.1 Favoured conformations of (v6-arene)tricarbonyIchromium(o) complexes for (a) an arene substituted with an idealised electron donating group (EDG), (b) an arene substituted with an idealised electron withdrawing group (EWG), and (c) an arene substituted with the methylsulfonyl group [dihedral angle C(2)-X-Cr-C(8) = 1 1.2', where X = the calculated centroid of the six ring carbons]. An accurate determination of the structure of this complex has already been reported (R = 2.8%)(ref. 7). 2576 J. Chem. SOC.,Perkin Trans. I, 1996 chromatography and crystallisation gave white crystals which were identified as the novel para-disubstituted arene, 1-(tert-butylsu1fonyl)-4-( 1 -cyano- 1 -methylethyl)benzene 5a (83%), on the basis of their microanalytical data and their IR, 'H NMR, I3C NMR and mass spectra.Similarly, addition of ILiCHS(CH,),S, BrMgCH2CH=CH, and LiCH,CO,Bu' to complex 4 led to the novel para-disubstituted arenes 5b, 5c and 5d in 67, 43 and 97% yield respectively. [It is of note that the reaction between BrMgCH,CH=CH, and the unsubstituted complex, (q6-benzene)tricarbonylchromium(o), gave < 5% of product ' thus suggesting that the electron-withdrawing tert- butylsulfonyl group activates the arene towards less reactive nucleophiles] . The strong preference for para-substitution, and thus presumably para nucleophilic attack, may be rationalised either by simple substituent-derived charge density arguments and/or by invoking the directing effect of the tricarbonylchromium(0) unit.The latter theory, which accounts for the majority of the results recorded in this area to date, proposes that nucleophilic attack occurs preferentially at arene carbons that are eclipsed by the carbonyl groups.12 Structural studies on a reasonably extensive series of (q6-arene)tricarbonylchromium(o) com-plexes have led to the generalisation that electron donating groups favour the syn-eclipsed structure [Fig. 1(a)] whilst electron withdrawing substituents favour the anti-eclipsed structure [Fig. l(b)], and this has been rationalised theo- retically.' Examination of the X-ray crystallographic analysis of [q6-(methylsulfony1)benzene)tricarbonylchromium(o) re-vealed that in the solid state this complex adopts an anti- eclipsed conformation in which the metal carbonyls essentially eclipse the ortho and para carbons of the arene ring [Fig.l(c)]. Thus, assuming that attack at the ortho position is disfavoured on steric grounds (and that the structure of [q6-(methyl- sulfonyl)benzene]tricarbonylchromium(o) and complex 4 are analogous), our observation that nucleophilic attack on [q6-(tert-butylsulfonyl)benzene]tricarbonylchromium(o) 4 occurs predominantly at the para position is consistent with the theory that the conformational preference of the tricarbonyl- chromium(o) unit exerts significant control over the site of nucleophilic attack. Deprotonation-electrophilic quench studies Studies and applications of ring deprotonation of (q6-arene)tricarbonylchromium(o) complexes have mainly em-ployed strong bases such as butyllithium to date.6 The regioselectivity of deprotonation by butyllithium followed by an electrophilic quench has been investigated for several substituents and may be summarised as follows.For alkyl substituents, the regioselectivity is generally poor and little development of this reaction has occurred. In contrast, fluoro substituents give good ortho selectivity and a range of electrophiles have been introduced in good yield; experiments with chloro and heavier halide substituents, however, led either to metal-halogen exchange or benzyne formation. Ether substituents give very high ortho selectivity (except if the substituent is very bulky, in which case meta-substitution is observed), and a good range of electrophiles may be introduced; as a result this system has found many applications.Amine substituents give predominantly meta-substitution and this has been rationalised by considering the favoured syn-eclipsed conformation of the tricarbonylchromium(0) unit [Fig. 1(a)] which is believed to lead to electron deficiency at the ring carbons eclipsed by the metal carbonyls. Some disubstitution products were observed during the course of the investigations summarised above, but, on the whole, attention was focused on monosubstitution and such products were disregarded. Monosubstitution of [q6-(tert-butylsu1fonyl)benzene)tri-carbonylchromium(0) 4 initially proved problematic.Using several sets of conditions and bases, only mixtures of monosubstituted product, disubstituted product and starting material were obtained. Eventually, monosubstitution was achieved in acceptable yield by exploiting the difference in solubility between complex 4 and its lithiated species. Thus the reaction was carried out in a 1 :2 mixture of THF and diethyl ether, which was found to be the solvent system required to just solubilise complex 4 at -78 "C. Addition of 1.0 equiv. of butyllithium to 4 at -78 "C, stirring for 1 h at -78 "C followed by quenching with chlorotrimethylsilane or methyl chlorofor- mate and stirring at -78 "C for 1 h gave, after work-up, the novel monosubstituted products 6a and 6b in good yield (80 and 74% respectively).Disubstitution of complex 4 proved much less troublesome. After adding 2.1 equiv. of butyllithium to complex 4 in THF at -78 "C,the reaction mixture was stirred for 15 min at -78 "C. The reaction mixture was then treated with chlorotrimethylsilane, chlorodiphenylphosphine, dimethyl disulfide or methyl chloroformate at -78 "C and stirred at this temperature for 1 h. After work-up, the novel disubstituted products 7a-d were isolated in 87, 90, 69 and 40% yield respectively. Introduction of two different ortho substituents onto 4 also proved possible once the conditions for clean monolithiation had been established. Thus execution of a one-pot double deprotonation-quench sequence on 4 led to the synthesis of [q6-l-(tert-butylsulfonyl)-2-(trimethylsilyl)-6-(diphenylphosphino)benzene]tricarbonylchromium(0) 8 in moderate yield (48%).The results described above indicate that deprotonation of complex 4 occurs preferentially at its ortho positions when butyllithium is used, an observation which is probably best explained by invoking a combination of the strong inductive effect of the tevt-butylsulfonyl substituent and coordination of the lithium counterion of the base to the sulfonyl substituent (lithiation of the uncomplexed analogue of 4 also occurs at the ortho position 14), but is also consistent with the anti-eclipsed conformation of the tricarbonylchromium(o) rotor. Although butyllithium has been used for the majority of deprotonation studies to date, a small number of investigations have used hindered bases such as lithium diisopropylamide (LDA) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP) '' to deprotonate (q6-arene)tricarbonylchromium(o) complexes.Recent interest in using chiral hindered bases to desymmetrise (q6-arene)tricarbonylchromium(o) complexes means in-creasing attention is now being given to how relatively hindered amide bases interact with these complexes. In view of this, we decided to investigate deprotonation of complex 4 using LiTMP as the base and chlorotrimethylsilane as the electrophilic quench. Addition of complex 4 to 1 .O equiv. of LiTMP at -78 "C, stirring at -78 "Cfor 10 min, addition of chlorotrimethylsilane, further stirring at -78 "C for 1 h and subsequent work-up gave the same product as was obtained when butyllithium was used as the base (6a) (Scheme 2).In contrast, addition of complex 4 to 2.0 equiv. of LiTMP at -78 "C followed by a chlorotrimethylsilane quench gave a disilylated product which from its spectroscopic data was clearly not 7a, the product obtained when butyllithium was used as the base. The new product was tentatively identified as [q6-1-(rut-butylsulfony1)-2,5-bis(trimethylsilyl)benzene]tricarbonylchromium(0) 9 from its spectroscopic and microanalytical data and was con-firmed as such by an X-ray crystallographic analysis (Fig. 2). Finally, to our surprise, addition of complex 4 to 3.5 equiv. of LiTMP at -78 "C followed by a chlorotrimethylsilane quench gave the 2,4,6-trisilylated product 10 in acceptable yield (50%).S(O)~BU'i S(0)2BurI @Cr(CO), 4 iii\ 9 MqSi SiMe3 10 Scheme 2 Reagents: i, LiTMP (I equiv.), then Me,SiCI, 51%; ii, LiTMP (2 equiv.), then Me,SiCl, 59%; LiTMP (3.5 equiv.), then Me,SiCI, 50% h C(12) Fig. 2 Molecular structure of complex 9 (C,,H,,CrO,SSi,). Selected bond lengths (A) and bond angles (O): C(l)-C(2) 1.420(5), C(2)-C(3) I .438(6), C(3)-C(4) 1.399(6), C(4)-C(5) 1.415(6), C(5)-C(6) 1.399(5), C(6)-C( 1) 1.425(5), C( 1)-S(7) 1.784(4), C(2)-Si( 14) 1.932(4) and C(5)- Si( 18) 1.894(4); C(22)-Cr-C(24) 88.2(2), C(24)-Cr-C(26) 87.9(2), C(26)-Cr-C(22) 85.1(2), Cr-C(22)-O(23) 177.5(4), Cr-C(24)-O(25) 176.9(4) and Cr-C(26)-O(27) 178.8(4). The production of the 2,5-disubstituted product 9 from the LiTMP reaction contrasts not only with the isolation of the 2,6- disubstituted product 7a from the BuLi-promoted reaction reported in this paper, but also with the isolation of a 2,6-disubstituted dideuteriated product from the reaction of the phenylsulfinyl analogue of complex 4 with 2 equiv.of LDA followed by a CD,OD quench.'* It is consistent, however, with the observation of some 2,5-disubstituted material in the product mixture obtained on reacting (q6-anisole)tricarbonyl-chromium(o) with one equivalent of LDA followed by a chlorotrimethylsilane quench.Id It thus appears that the combination of a hindered amide base and a relatively bulky electrophile provides access to 2,5-disubstituted systems presumably by facilitating anion equilibration and promoting electrophilic attack at a relatively unhindered site.Finally, the introduction of three substitutents onto an (q6-arene)tricarbo- nylchromium(0) complex by a deprotonation-quench sequence is, to the best of our knowledge, unprecedented. We tentatively J. Chem. SOC.,Perkin Trans. I, 1996 2577 propose that this occurs via dilithiation of in situ generated 6a, although the formation of a trianion cannot be entirely discounted. Experimental All reactions were performed under nitrogen using standard vacuum line and Schienk tube techniques." Reactions and operations involving (arene)tricarbonylchromium(o)complexes were protected from light. Tetrahydrofuran (THF), diethyl ether and 1,4-dioxane were distilled from sodium benzophenone ketyl.Chlorotrimethylsilane, dimethyl disulfide, 1,3-dimethyI- 3,4,5,6-tetrahydropyrimidin-2(1H)-one (DMPU), isobutyroni- trile, tert-butyl acetate and 2,2,6,6-tetramethylpiperidine (TMP) were distilled from CaH,. Methyl chloroformate and acetyl chloride were distilled from K2C03. I ,3-Dithiane was sublimed at 40 "C under vacuum (0.1 mmHg). All other reagents were used as obtained from commercial sources. The concentrations of but ylli th ium and met h yllithium were determined by titration against diphenylacetic acid.,' Column chromatography was performed on silica gel (40-63 pm, BDH Laboratory Supplies). Light petroleum (bp 40-60 "C) was redistilled for all column chromatography. Melting points were obtained on a Gallenkamp capillary melting point apparatus and are uncorrected.Elemental analyses were performed by the Imperial College Microanalyti- cal Service. IR Spectra were obtained on Mattson 5000 FTIR and Perkin-Elmer 1710 FTTR instruments. NMR Spectra were recorded in CDCI, at room temperature on Bruker AM 300 and Bruker AM 500 spectrometers. J Values are given in Hz. Mass spectra were recorded on VG Micromass 7070E and AutoSpec-Q instruments using ET, CT and FAB (m-nitrobenzyl alcohol matrix) techniques. For clarity, the carbon atom attached to the iert-butylsulfonyl substituent in the [q6-(tert-butylsulfonyl)benzene]tricarbonylchromium(~) complexes is always denoted as C-I. (tevt-Butylsulfany1)benzene2879 To a 150 cm3 round-bottomed flask cooled in an ice bath were successively added acetic acid (10 cm3), perchloric acid (70% solution, 4 cm3) and acetic anhydride (6 cm3) and the solution was stirred for 20 min.Thiophenol 1(6.2 g, 56 mmol) and tert-butyl alcohol (5.0 g, 67 mmol) were added to the mixture, the volume of which was adjusted to 50 cm3 with acetic acid. The mixture was stirred for 2 h at room temperature, then diluted with saturated brine (25 cm3) and extracted with diethyl ether (4 x 25 cm3). The combined organic extracts were washed with saturated aqueous sodium hydrogen carbonate (3 x 50 cm3) and water (50 cm3) and then dried (MgSO,). Column chromatography (SiO,; light petroleum) gave the title sulfide as a colourless oil (8.6 g, 51.8 mmol, 93%); v,,,(neat)/cm~' 3073m, 3059m, 3033m and 3020m (C-H arom.) and 2961s, 2941s, 2922s, 2898s and 2861s (C-H alkyl); 6,(300 MHz) 1.31 [9 H, s, C(CH,),], 7.33-7.40 (3 H, m, ArH) and 7.54-7.57 (2 H, m, ArH); 6,{'H) (75 MHz) 30.9 [C(CH,),], 45.8 [C(CH,),], 128.4 (C-2,6 or -33, 128.6 (C-4), 132.7 (C-1) and 137.4 (C-2,6 or -33); m/z (EI, 70 eV, 200°C) 166 (M', 873, 77 (M -SC,H,, 89) and 57 (C,H,, 100).(tevt-Butylsu1fonyl)benzene 39910 A solution of (tert-buty1sulfanyl)benzene 2 (8.5 g, 51.2 mmol) in methanol (200 cm3) was cooled in an ice bath. To this was added a solution of Oxone" (47.2 g, 76 mmol) in water (200 cm3). The resulting slurry was stirred for 2 h at room temperature. Methanol was removed by evaporation under reduced pressure and the mixture was diluted with water (100 cm3) and extracted with diethyl ether (3 x 200 cm3).The combined organic layers were washed with water (2 x 300 cm3) and brine (2 x 300 cm3), and then dried (MgSO,). Solvent removal under reduced pressure gave a white solid, re-2578 J. Chem. SOC.,Perkin Trans. I, 1996 crystallisation of which from hexane yielded the title sulfone as white needles (9.1 g, 46.0 mmol, 90%); mp 98 "C (lit.,9 98-99 "C); ~,,,,,(CH,C~,)/C~-~ 3061m (C-H arom.), 2988m and 2936m (C-H alkyl) and 1297s and 1135s (S=O); 6,(300 MHz) 1.34 [9 H, s, C(CH,),], 7.54-7.59 (2 H, m, ArH), 7.64-7.67 (1 H, m, ArH) and 7.88-7.91 (2 H, m, ArH); 6,('H) (75 MHz) 23.6 [C(CH,>,], 59.8 [C(CH,),], 128.6 (C-2,6 or -33, 130.4 (C-2,6 or -33, 133.5 (C-4) and 135.3 (C-I); mjz (EI, 70 eV, 200°C) 198 (M+, 1%), 125 (M -0 -C4H9, 4), 77 (M -S02C4H9, 12) and 57 (C,H,, 100).[q6-(tevt-Buty lsulfon yl)benzene] tricarbonylchromium(o) 4 (tert-Butylsu1fonyl)benzene 3 (2.0 g, 10.1 mmol) and hexacarbonylchromium(0) (4.5 g, 20.5 mmol) in nitrogen- saturated 1,4-dioxane (250 cm3) were placed in a 500 cm3 round-bottomed flask fitted with a Liebig air condenser with a water condenser on top, and heated under reflux, with stirring, for 4 days. The resulting mixture was cooled in an ice bath and filtered through Kieselguhr, eluting with diethyl ether. The filtrate was concentrated under reduced pressure leaving a yellow solid which was purified by column chromatography (SiO,; light petroleum-dichloromethane, 3 :I to 1 :3 gradient).Crystallisation from dichloromethane gave the title complex as yellow crystals (2.3 g, 6.9 mmol, 68%); mp 179 "C (Found: C, 46.7; H, 4.3. C13Hl,Cr0,S requires C, 46.71; H, 4.22%); v,,,(CH,Cl,)/cm-' 1996vs and 1935vs (CEO); 6,(300 MHz) 1.42[9 H, s, C(CH,),], 5.14 (2 H, t, J6.2, ArH metcr),5.59 (1 H, t, J 6.2, ArH para) and 5.88 (2 H, d, J 6.2, ArH ortho);6,('H) (75 MHz) 23.7 [C(CH,),], 60.3 [C(CH,>,], 85.8 (C-2,6 or -3,5), 94.4 (C-4), 94.9 (C-2,6 or -3,5),99.2 ((2-1) and 228.9 [Cr(CO),]; m/z (EI, 70 eV, 200 "C) 334 (M', 279, 278 (M -2C0,4), 250 (M -3C0, 18), 57 (C,H,, 40) and 52 (Cr, 100). l-(tert-Butylsulfony1)-4-(1-cyano-1 -methylethyl)benzene 5a Lithium diisopropylamide (0.27 cm3 of a 1.35 M solution in cyclohexane, 0.36 mmol) was added to a solution of isobutyronitrile (0.033 cm3, 0.36 mmol) in dry nitrogen- saturated THF (2 cm3) in a Schlenk tube kept at -78 "C. The reaction mixture was stirred for 15 min at 0 "C and cooled again to -78 "C.To this were successively added DMPU (0.11 cm3, 0.9 mmol) and a solution of [q6-(tert-butyl-sulfonyl)benzene]tricarbonylchromium(o) 4 (1 00 mg, 0.30 mmol) in dry nitrogen-saturated THF (2 cm3). After stirring at 0 "C for 1.5 h, the reaction mixture was quenched with iodine (381 mg, 1.50 mmol) at -78 "C and stirred for 1 day at room temperature. It was then partitioned between diethyl ether (2 x 20 cm3) and 20% aqueous sodium hydrogen sulfite (20 cm'). The organic layers were washed with water (20 cm3) and saturated brine (20 cm3), dried (MgSO,) and concentrated to leave a white solid.Column chromatography (SiO,; light petroleum-dichloromethane, 1 : 1 to 0: 1 gradient) gave the title product (67 mg, 0.25 mmol, 83%) which crystallised from hexane-dichloromethane as white crystals; mp I50"C (Found: C, 63.1; H, 7.0; N, 5.2. C14H19N02Srequires C, 63.37; H, 7.22; N, 5.28%); v,,,(CHCl,)/cm ' 3058m, 3056m and 3019m (C-H arom.), 2981m, 2940m, 2913m and 2875m (C-H alkyl), 2243w (C=N), 1214vs and 1101s (SO); 6,(300 MHz) 1.36 [9 H, s, C(CH,),], 1.76 [6 H, s, C(CH,),(CN)], 7.67 (2 H, d, J 8.5, H-3,5) and 7.92 (2 H, d, J 8.5, H-2,6); 6,{ 'H) (75 MHz) 23.6 [C(mJJ, 28.9 [C(m3),(CN)], 37.4 [C(CH,),(CN)], 60.0 [C(CH,),], 123.5 (CN), 125.6(C-3,5), 131.2(C-2,6), 135.3 (C-4) and 147.2 (C-I); m/z (CI, NH,) 283 (MNH,', 100%).l-(tevt-Butylsulfonyl)-4-[241,3-dithianyl)] benzene 5b The general procedure was the same as described for the preparation of compound 5a. Butyllithium (0.22 cm3 of a 1.67 M solution in hexanes, 0.36 mmol) was added to a solution of 1,3- dithiane (43 mg, 0.36 mmol) in THF (2 cm3) at -78 "C and the mixture was stirred for 20 min at -20 "C and recooled to -78 "C. To this were successively added DMPU (0.11 cm3, 0.9 mmol) and a solution of 4(100 mg, 0.30 mmol) in THF (2 cm3) at -78 "C. After stirring at 0 "C for 1.5 h, the reaction was quenched with iodine (381 mg, 1.50 mmol) at -78 "C and stirred for 1 day at room temperature. A white solid was obtained after the usual work-up.Column chromatography (SiO,; light petroleum-dichloromethane, 1 : 1 to 0: 1 gradient) gave the title product (63 mg, 0.20 mmol, 67%) which crystallised from hexane-dichloromethane as white needles; mp 189 "C (Found: C, 52.9; H, 6.1. C14H2002S3 requires C, 53.13; H, 6.37%); v,,,(CHCl,)/cm-' 3076m, 3070m and 3020m (C-H arom.), 2989m, 2976m, 2956m, 2937m and 2906m (C-H alkyl) and 1214vs and 1134vs (S=O); 6,(300 MHz) 1.34 [9 H, s, C(CH,),], 1.90-2.07 (1 H, m, SCH,CHHCH,S), 2.19-2.27 (I H, m, SCH,CHHCH,S), 2.90-3.15 (4 H, m, SCH,CH,CH,S), 5.23 (I H, s, ArCH), 7.66 (2 H, d, J8.3, H-3,5) and 7.87 (2 H, d, J 8.3, H-2,6); 6,i'H) (75 MHz) 23.6 [C(CH,),], 24.9 (SCH,CH,CH,S), 3 1.9 (SCH,CH,CH,S), 50.6 (ArCH), 59.9 [C(CH,),], 128.3 (C-33) 130.9 (C-2,6), 135.4 (C-4) and 144.9 (C-1); m/z (ET, 70 eV, 200OC) 316 (M', 973, 260 (MH -C4H9, 17), 196 (MH -SO,C,H,, 13), 121 (S0,C4H9, 10) and 57 (C4H9,lOO).4-Allyl-l-(tert-butyIsulfonyl)benzene5c The general procedure was the same as described for the preparation of compound Sa.A solution of 4 (100 mg, 0.30 mmol) in THF (2 cm3) at -78 "C was transferred via a cannula to a mixture of allylmagnesium bromide (0.45 cm3 of a 1.0 M solution in diethyl ether, 0.45 mmol) and DMPU (0.16 cm3, 1.3 mmol) in THF (2 cm3) kept at -78 "C. The reaction mixture was stirred for 1.5 h at 0 OC, quenched with iodine (38 1 mg, 1SO mmol) and stirred for 1 day at room temperature. After the usual work-up, purification by column chromatography (SiO,; light petroleum-diethyl ether, 4: 1) gave the titleproduct (31 mg, 0.13 mmol, 43%) which crystallised from Rexane as white crystals; mp 62 "C (Found: C, 65.2; H, 7.4.C,,H,,O,S requires C, 65.51; H, 7.61%); v,,,(CHCl,)/cm~' 3055m (C-H arom.), 2987m, 2954m, 2931m, 2871m and 2854m (C-H alkyl and alkenyl); 6,(300 MHz) 1.34 [9 H, d, C(CH,),], 3.49 (2 H, s, ArCH,), 5.10-5.18 (2 H, m, CHCH,), 5.90-6.05 (1 H, ddt, J 6.7, 10.2, 16.9, CHCH,), 7.38 (2 H, d, J8.2, H-33) and 7.81 (2 H, d, J 8.2, H-2,6); Sc('H) (125.8 MHz) 23.6 [C(CH3),], 40.0 (Arm,), 59.7 [C(CH,),], 1 17.2 (CHCH,), 128.9 (C-33,130.6 (C-2,6), 133.1 (C-4), 135.8 (CHCH,) and 146.4 (C-1); m/z (CI, NH3) 256 (MNH,+, loo%), 239 (MH, 2), 182 (MH -C4H9, 3), 118 (MH -S02C4H9, 4) and 57 (C,H,, 3).4-(tert-Butoxycarbony1methy1)-1-(tert-butylsulfony1)benzene 5d The general procedure was the same as described for the preparation of compound 5a. Lithium diisopropylamide (0.27 cm3 of a 1.35 M solution in cyclohexane, 0.36 mmol) was added to a solution of tert-butyl acetate (0.048 cm3, 0.36 mmol) in THF at -78 "C. After this mixture had been stirred for 30 min, DMPU (0.11 cm3, 0.9 mmol) and a solution of 4(100 mg, 0.30 mmol) in THF were successively added. After 1.5 h at 0 "C, the reaction mixture was quenched with iodine (381 mg, 1SO mmol) at -78 "C and stirred for 1 day at room temperature. After the usual work-up, column chromatography (SiO,; diethyl ether) gave the title product (90 mg, 0.29 mmol, 97%) which crystallised from hexane as white needles; mp 97 "C (Found: C, 61.4; H, 7.6.C,,H,,O,S requires C, 61.51; H, 7.74%); V~~~(CH,C~,)/C~-~'3058w (C-H arom.), 2981m, 2954m, 2935m, 2906m, 2873m (C-H alkyl), 1730s (M)and 1265vs and 1133vs (S=O); 6,(300 MHz) 1.34 19 H, s, SO,C(CH,),], 1.44[9 H, s, CO,C(CH,),], 3.64 (2 H, s, ArCH,), 7.45 (2 H, d, J 8.3, H-33) and 7.84 (2 H, d, J 8.3, H-2,6); 6,{'H) (75 MHz) 23.6 [S02C(CH3),], 28.0 [CO,C(CH,),], 42.4 (ArCH2), 59.8 [SO,C(CH,)J, 81.6 [CO,C(CH,),], 129.6 (C-3,5), 130.6 (C- 2,6), 134.0 (C-4), 140.8 (C-1) and 169.6 (CO,); m/z (CI, NH,) 330 (MNH4+, 100%) and 274 (MNH, -C4H9, 9). [q6-1-(ter~-B~tylsulfonyl)-2-(trimethylsilyl)benzene]tri-carbonylchromium(0)6a [~6-(tert-Butylsulfonyl)benzene]tricarbonylchromium(o) 4 (1 50 mg, 0.45 mmol) was dissolved in a mixture of dry nitrogen- saturated THF (4 cm3) and diethyl ether (8 cm3) in a Schlenk tube and cooled to -78 "C.Butyllithium (0.29 cm3 of a 1.54 M solution in hexanes, 0.45 mmol) was added. The reaction mixture was stirred for 1 h at -78 "C and chlorotrimethylsifane (0.086 cm3, 0.68 mmol) was then added. After stirring for 1 h at -78 "C, the mixture was allowed to warm to room temperature. The solvent was removed under reduced pressure. Column chromatography (SiO,; light petroleum-diethyl ether, 4: 1) gave the title complex (147 mg, 0.362 mmol, 80%) which crystallised from hexane-diethyl ether as orange crystals; mp 119-120 "C (Found: C, 47.0; H, 5.4. CI6H,,CrO5SSi requires C, 47.28; H, 5.46%); v,,,(CH,Cl,)/cm-' 1982vs and 1920vs (CEO) and 1248s and 1134s (S=O); 6,(300 MHz) 0.48 [9 H, s, Si(CH,),], 1.43 [9 H, s, C(CH,),], 5.2 (1 H, t, J6.2, ArH), 5.46 (1 H, d, J 6.5, ArH) and 5.61-5.70 (2 H, m, ArH); 6,('H} (75 MHz) 2.8 [Si(CH,),], 24.7 [C(CH3)3J, 62.6 [C(CH,),], 89.9, 90.1, 92.1 and 99.2 (C-3,4,5,6), 99.0 (C-2), 113.4 (C-I) and 230.4 [Cr(CO),]; m/z (EI, 70 eV, 200 "C) 406 (M', 279, 350 (M -2C0, 7), 322 (M -3C0, 40), 271 (MH -3CO -Cr, 3), 73 (SiC,H,, 29),57 (C4H,, 87) and 52 (Cr, 100).[q6-1-(tert-Butylsulfonyl)-2-(methoxycarbonyl)benzene] tri-carbonylchromium(o)6b The general procedure was the same as described for the preparation of complex 6a. Complex 4 (150 mg, 0.45 mmol) was treated with butyllithium (0.29 cm3 of a 1.54 M solution in hexanes, 0.45 mmol) and methyl chloroformate (0.042 cm', 0.54 mmol).Column chromatography (SiO,; light petroleum- diethyl ether, 1 : 1) gave the title complex (131 mg, 0.334 mmol, 74%) which crystallised from hexane-dichloromethane as yellow needles; mp 140°C (Found: C, 45.7; H, 4.0. C,,H,,CrO,S requires C, 45.92; H, 4.1 1%); vmax(CH,- Cl,)/cm--' 1940vs and 1932vs (Ca) and 1739m (GO); 6,(500 MHz) 1.48 [9 H, s, C(CH,),J, 3.91 (3 H, s, CO,CH,), 5.14-5.18 (2 H, m, ArH), 5.76 (1 H, td, J 6 and 0.5, ArH) and 5.53 (1 H, dd, J 6 and 0.5, ArH ortho); S,('H) (125.8 MHz) 24.4 [C(CH,>,], 53.8 (C02CH3), 62.6 [C(CH,),], 85.8, 86.6, 91.6, 93.2 (C-3,4,5,6), 98.8, 106.8 (C-1,2), 165.5 (COZCH,) and 228.1 [Cr(CO),]; m/z (CI, NH,) 410 (MNH,', loo%), 393 (MH, 20), 319 (MH -C0,Me -CH,, 43) and 52 (Cr, 2)* [q6-1-(tert-Butylsulfonyl)-2,6-bis(trimethylsilyl)benzene] tri-carbonylchromium(o) 7a [q "-(tevt-Butylsulfonyl)benzene] tricarbonylchromium(o) 4 (100 mg, 0.30 mmol) was dissolved in dry nitrogen-saturated THF (6 cm3) in a Schlenk tube and cooled to -78 "C with stirring.Butyllithium (0.39 cm3 of a 1.60 M solution in hexanes, 0.62 mmol) was added to that solution. The mixture was stirred for 15 min. To this was added, via a cannula, a solution, of chlorotrimethylsilane (0.114 cm3, 0.90 mmol) in nitrogen- saturated THF (2 cm3) at -78 "C. After stirring at -78 "C for 1 h, the reaction mixture was allowed to warm to room temperature. Removal of the solvent under reduced pressure produced a brown solid.Purification by column chromatogra- phy (SiO,; light petroleum-diethyl ether, 1 :1) afforded the title complex (125 mg, 0.262 mmol, 87%) which crystalkd from hexane-diethyl ether as orange-red needles; mp 149 "C (Found: C, 47.7; H, 6.0. C,,H,,CrO,SSi, requires C, 47.68; H, 6.32%); v,,,(CH,Cl,)/cm-' 1977vs and 1915vs (CzO); 6,(300 MHz) 0.53 [18 H, s, Si(CH,),], 1.32 [9 H, s, C(CH,),], 5.00 (1 H, t, J 6.4, ArH) and 6.06 (2 H, d, J6.4, ArH); 6,{ 'H) (1 25.8 MHz) 5.1 [Si(CH,),], 25.8 [C(CH,),], 64.2 [C(CH,),], 90.3 (C-4), 96.9 (C-2,6), 103.2 (C-3,5), 122.0 (C-1) and 231.6 [Cr(CO),J; m/z (EI, 70 eV, 220 "C) 478 (M', 1.479, 406 (MH -SiC3H9, l), 422 (M -2C0, l), 394 (M -3C0, 5), 343 (MH -3CO -J.Chem. SOC.,Perkin Trans. 1,1996 2579 Cr, 3), 271 (MH -3CO -Cr -SiC,H,, 7), 73 (SiC,H,, 51), 57 (C4H,, 38) and 52 (Cr, 100). [q6-1-(tert-Butylsulfonyl)-2,6-bis(diphenylphosphino)benzene] -tricarbonylchromium(o) 7b The general procedure was the same as described for the preparation of complex 7a. Complex 4 (100 mg, 0.30 mmol) was treated with butyllithium (0.38 cm3 of a 1.67 M solution in hexanes, 0.63 mmol) and chlorodiphenylphosphine (0.176 cm3, 0.90 mmol). Column chromatography (SiO,; light petroleum- dichloromethane, 3 : 1 to 1:3 gradient) afforded the title complex (190 mg, 0.270 mmol, 90%) which crystallised as orange needles; mp 165-167 "C (decomp.) (Found: 703.0963. C3,H,,Cr0,P,S requires 703.0929); v,,,(CH,Cl,)/cm-' 1990vs and 1927vs (Ca); d,(300 MHz) 1.60 [9 H, s, C(CH,),], 4.95-5.05 (1 H, br s, H-4), 5.55-5.70 (2 H, br s, H-3), 7.22-7.27 (4 H, m, ArH), 7.32-7.42 (12 H, m, ArH) and 7.57-7.72 (4 H, m, ArH); m/z (FAB positive) 703 (MH+, 24%), 618 (MH -3C0, 38), 592 (MH -3CO -C4H9, 36), 497 (M -3CO -S02C4H9, loo), 77 (C,H,, 11) and 52 (Cr, 48).[~6-1-(tert-Butylsulfonyl)-2,6-bis(methylsulfanyl)benzene]tri-carbonylchromium(0) 7c The general procedure was the same as described for the preparation of complex 7a. Complex 4 (100 mg, 0.30 mmol) was treated with butyllithium (0.38 cm3 of a 1.67 M solution in hexanes, 0.63 mmol) and dimethyl disulfide (0.081 cm3, 0.90 mmol). Column chromatography (SiO,; light petroleum- diethyl ether, 1 : 1) afforded the title complex (88 mg, 0.207 mmol, 69%) which crystallised from dichloromethane as orange crystals; mp 144 "C (Found: C, 42.0; H, 4.1. CISHl,CrO,S, requires C, 42.24; H, 4.25%); v,,,(CH,Cl,)/cm~' l984vs and 1921vs (Ca); 6,(300 MHz) 1.59 [9 H, s, C(CH,),], 2.39 [6 H, s, S(CH,)], 4.94 (2 H, d, J 6.5, ArH) and 5.84 (1 H, t, J 6.5, ArH); 6,('H) (125 MHz, CD,CI,) 18.4 (SCH,), 26.0 [C(CH3)3], 66.3 [C(CH3),], 83.5 (C-3,5), 95.0 (C-4), 99.3 (C- I), 121.8 (C-2,6) and 230.5 [Cr(CO),]; m/z (CI, NH,) 444 (MNH,+, loo%), 398 (M -CO, 4), 308 (MNH, -3CO -Cr, 60), 252 (MNH, -3CO -Cr, 35), 234 (MH -3CO -Cr -C4H9, 9), (MH -3CO -Cr -C4H9 -CH,, 58) and 52 (Cr, 10).[$-I -(tert-Butylsulfonyl)-2,6-bis(methoxycarbonyl)benzene] tri- carbonylchromium(0)7d The general procedure was the same as described for the preparation of complex 7a.Complex 4 (100 mg, 0.30 mmol) was treated with butyllithium (0.38 cm3 of a 1.67 M solution in hexanes, 0.63 mmol) and methyl chloroformate (0.070 cm3, 0.90 mmol). Column chromatography (SiO,; light petroleum- dichloromethane, 1 :1 to 0: 1 gradient) afforded the title complex (54 mg, 0.120 mmol, 40%) which crystallised from hexane-dichloromethane as dark orange needles; mp 153 "C (Found: C, 45.1; H, 3.8. C,,H,,CrO,S requires C, 45.34; H, 4.03%); v,,,(CH,Cl,)/cm~ ' 2008vs and 1946vs (CEO), 1741s (M);6,(300 MHz) 1.60 [9 H, s, C(CH,),], 3.96 (6 H, s, C02CH3),5.28(2H,d,J6.2,ArH)and5.52(1H,t, J6.2,ArH); S,--'H) (125.8 MHz, CD2C12) 26.8 [C(CH3),], 53.9 (C02CH3), 67.8 [C(CH,),], 89.1 (C-3,5), 89.6 (C-4), 102.5 (C-1), 103.8 (C- 2,6), 166.6 (CO,CH,) and 228.3 [Cr(CO),]; m/z (CI, NH,) 468 (MNH4+, 67%), 410 (MH -SO,C,H,, 5), 377 (MH -CH, -CO,CH,, IOO), 332 [MNH, -Cr(CO),, 81, 136 [Cr(CO),, 31 and 52 (Cr, 4).[$-I -(teut-Butylsulfonyl)-2-(trimethylsilyl)-6-(diphenyl-phosphino)benzene] tricarbonylchromium(o) 8 [q6-( tert-Butylsu1fonyl)benzenejtricarbonylchromium(o) 4 (150 mg, 0.45 mmol) was dissolved in a mixture of dry nitrogen- saturated THF (4 cm3) and diethyl ether (8 cm3) in a Schlenk tube and cooled to -78 "C. Butyllithium (0.29 cm3 of a 1.54 M solution in hexanes, 0.45 mmol) was added. The reaction 2580 J. Chem. SOC.,Perkin Trans. I, 1996 mixture was stirred for 45 min at -78 "C and then chlorotrimethylsilane (0.057 cm3, 0.45 mmol) was added.After stirring for 30 rnin at -78 "C, butyllithium (0.29 cm3 of a 1.54 M solution in hexanes, 0.45 mmol) was added and, after 30 min, chlorodiphenylphosphine (0.129 cm3, 0.66 mmol) was added. The mixture was stirred for 30 min at -78 "C and then allowed to warm to room temperature. The solvent was removed under reduced pressure. Column chromatography (SiO,; light petroleum-dichloromethane, 4: 1) gave the title complex (127 mg, 0.21 5 mmol, 48%) which crystallised from hexane4iethyl ether as orange crystals; mp 160 "C (decomp.) (Found: C, 56.9; H, 5.4. C,,H,,CrO,PSSi requires C, 56.94; H, 5.29%); v,,,(CH,Cl,)/cm~' 1982vs and 1921vs (Ca); 6,(300 MHz) 0.52 [9 H, s, Si(CH,),], 1.48 [9 H, s, C(CH,),], 4.99 (1 H, t, J6, H-4), 5.89 (1 H, d, J6, H-5), 5.95 (1 H, d, J6, H-3), 7.29-7.40 (8 H, m, ArH) and 7.61-7.70 (2 H, m, ArH); 6,{'H} (125.8 MHz, CD,CI,) 5.0 [Si(CH,),], 27.7 [C(CH,),], 65.9 [C(CH,),], 88.7 (C-4), 99.3 (C-2), 102.4, 102.7 (C-3,5), 103.4 (C-1), 125.5 (d, J 28, C-6), 128.5, 128.9, 130.0, 130.2 (4 x ArH meta and 2 x ArH para), 134.2 (d, J 18, ArH ortho), 136.7 (d, J 23, ArH ortho), 140.2 (d, J 16, ArH ipso), 141.7 (d, J 22, ArH @so)and 232.3 [Cr(CO),]; m/z (CI, NH,) 591 (MH', 85%), 535 (MH -2C0, 28), 469 (M -S02C4H9, 30), 455 (MH -3CO -Cr, 13) and 335 (MH -3CO -Cr -SO,C,H,, 100).[$-1-(tevt-Butylsulfonyl)-2-(trimethylsilyl)benzene] tri-carbonylchromium(o) 6a Methyllithium (0.21 cm3 of a 1.40 M solution in diethyl ether, 0.30 mmol) was added to a solution of 2,2,6,6-tetramethylpiperi- dine (0.061 cm3, 0.36 mmol) in dry nitrogen-saturated THF (2 cm3) maintained in a Schlenk tube at -78 "C.The mixture was stirred for 30 rnin at 0 "C then recooled to -78 "C. To this was added a solution of complex 4 (100 mg, 0.30 mmol) dissolved in dry nitrogen-saturated THF (3 cm3) and cooled to -78 "C. The mixture was stirred for 10 rnin and chlorotrimethylsilane (0.076 cm3, 0.60 mmol) was added. After stirring at -78 "C for 1 h, the cold bath was removed and the reaction mixture was allowed to warm to room temperature. The solvent was removed under reduced pressure. Purification by column chromatography (SO,; light petroleum-diethyl ether, 4 : I) afforded the title complex (62 mg, 0.153 mmol, 51%) which crystallised from dichloromethane as yellow needles.Spectro- scopic data were identical to those obtained from a fully characterised sample of complex 6a. [q6-1-(teut-Butylsulfonyl)-2,5-bis(trimethylsilyl)benzene] tri-carbonylchromium(0)9 Methyllithium (0.43 cm3 of a 1.40 M solution in diethyl ether, 0.60 mmol) was added to a solution of 2,2,6,6-tetramethylpiperi- dine (0.111 cm3, 0.66 mmol) in dry nitrogen-saturated THF (2 cm3) maintained in a Schlenk tube at -78 "C. The mixture was stirred for 30 rnin at 0 "C and then recooled to -78 "C. To this was added a solution of complex 4 (100 mg, 0.30 mmol) dissolved in dry nitrogen-saturated THF (3 cm3) and cooled to -78 "C. The mixture was stirred for 15 min andchlorotrimethyl- silane (0.1 14 cm3, 0.90 mmol) was added.After stirring at -78 "C for 30 min, the reaction mixture was allowed to warm to room temperature. Removal of the solvent under reduced pressure left a brown oil. Purification by column chromatogra- phy (SiO,; dichloromethane-light petroleum, 4 :1) afforded the title complex (85 mg, 0.178 mmol, 59%) which crystallised from hexane-diethyl ether as yellow needles; mp 144 "C (Found: C, 47.5; H, 6.1. C19H,,Cr05SSi, requires C, 47.68; H, 6.32%); v,,,(CH2C12)/cm~' 1982vs and 1915vs (C=O); 6,(500 MHz) 0.34 [9 H, s, Si(CH,),], 0.47 [9 H, s, Si(CH,),], 1.41 [9 H, s, C(CH,),], 5.34 (2 H, s, ArH) and 5.59 (1 H, s, ArH); 6,('H) (125.8 MHz) 2.5 [Si(CH,),], 24.7 [C(CH,),], 64.4 [C(CH,),], 95.9, 97.6, 96.9 (C-3,4,6), 97.9, 101.8 (C-2,5), 110.7 (C-1) and 230.2 [Cr(CO),]; m/z (EI, 70 eV, 180 "C) 478 (M+, 1.4%), 422 (M -2C0, l), 394 (M -3C0, 59, 343 (MH -3CO -Cr, 2), 271 (MH -3CO -Cr -SiC3H9, 21), 73 (SiC,H,, 53), 57 (C4H9, 46) and 52 (Cr, 100).[$-l-( teut-Butylsulfonyl)-2,4,6-tris(trimethylsilyl)benzene]tri-carbonylchromium(0)10 The general procedure was the same as described for the preparation of complex 9. Methyllithium (0.78 cm3 of a 1.35 M solutionin diethyl ether, 1.05 mmol) was added to a solution of 2,2,6,6-tetramethylpiperidine (0.192 cm3, 1.14 mmol) in THF (3 cm3) at -78 "C. The mixture was stirred for 30 min at 0 "C and then cooled to -78 "C. To this was added, via a cannula, a solution of 4 (100 mg, 0.30 mmol) in THF (3 cm3) cooled to -78 "C.Themixture was stirred for2 handchlorotrimethylsilane (0.152 cm', 1.20 mmol) was added.After stirring at -78 "C for 30 min, the cold bath was removed and the reaction mixture was allowed to warm to room temperature. Removal of the solvent under reduced pressure left a red oil. Purification by column chromatography (SiO,; light petroleumdichloromethane, 4 : 1 to 1 : 1 gradient) afforded the title complex (83 mg, 0.151 mmol, 50%) which crystallised from hexane-dichloromethane as orange needles; mp 192 "C (decomp.) (Found: C, 47.8; H, 6.8. C,,H,,CrO,SSi, requires C, 47.97; H, 6.95%); v,,,(CH2- Cl,)/cm 1977vs and 1915vs (GO); 6,(300 MHz) 0.30 [9 H, s, Si(CH,),], 0.53 [l8 H, s, 2 x Si(CH,),], 1.33 [9 H, s, C(CH,),] and 6.09 (2 H, s, ArH); &('H} (75 MHz) 5.3 [Si(CI-I,),], 27.0 [C(CH,),], 64.3 [C(CH,),], 96.2 (C-2,6), 99.3 (C-4), 107.7 (C-3,5), 124.2 (C-1) and 232 [Cr(CO),]; m/z(EI, 70 eV, 200°C) 550 (M', l%), 466 (M -3C0, 4), 343 (MH -3CO -Cr, 2), 73 (SiC,H,, 100) and 52 (Cr, 60).X-Ray crystallographic analysis of 9 Crystal data. C,,H,,CrO,SSi,, M = 478.7, monoclinic, spacegroup P2,/c,a = 11.459(8),b = 16.939(9),c = 12.918(6)A, /3 = 105.75(5)", V = 2413(3) A3, 2 = 4, D,= 1.32 g ern-,, Cu-Km radiation, i= 1.541 78 A, p(Cu-Ka) = 58.8 cm-', F(OO0) = 1008. Orange prismatic needles, crystal dimensions 0.30 x 0.20 x 0.16 mm. Data collection and processing. Data were measured on a Siemens P4/PC diffractometer with Cu-Ka radiation (graphite monochromator) using o-scans.Of the 3570 independent reflections measured (20 < 120"), 3066 had IF,\ > 4a(lF0J) and were considered to be observed. The data were corrected for Lorentz and polarisation factors and a Gaussian absorption correction (face-indexed numerical) was applied; the maximum and minimum transmission factors were 0.485 and 0.334 respectively. Structure analysis and refinement. The structure was solved by direct methods and the non-hydrogen atoms were refined anisotropically. The positions of the hydrogen atoms were idealised, assigned isotropic thermal parameters, U(H) = 1.2Ue,(C) [U(H) = 1.5Ue,(C-Me)] and allowed to ride on their parent atoms. Refinement was by full-matrix least-squares based on F2 to give R,= 0.050, wR, = 0.135 for 254 parameters.The maximum and minimum residual electron densities in the final AF map were 0.43 and -0.58 e A-3 respectively. The mean and maximum shift/error ratios in the final refinement cycle were 0.000 and 0.001 respectively. Computations were carried out on a 50 MHz 486 PC computer using the SHELXTL PC program system.2 Atomic coordinates, thermal parameters, and bond lengths and angles have been deposited at the Cambridge Crystallo- graphic Data Centre (CCDC). See Instructions for Authors, J. Chem. SOC., Perkin Trans. I, 1996, Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 207/52. References 1 Ringdeprotonation: (a)D. A. Price, N.S. Simpkins, A. M. MacLeod and A. P. Watt, f.Org. Chem., 1994,59, 1961; (b) E. P. Kundig and A. Quattropani, Tetrahedron Lett., 1994, 35, 6159; (c) M. Uemura, Y. Hayashi and Y. Hayashi, Tetrahedron: Asymmetry, 1994,5,1427; (d) H.-G. Schmalz and K. Schellhaas, Tetrahedron Lett., 1995, 36, 5515. 2 Benzylic deprotonation: (a)R. A. Ewin and N. S. Simpkins, Synlett, 1996, 317; (b) E. L. M. Cowton, S. E. Gibson (nee Thomas), M. J. Schneider and M. H. Smith, Chem. Commun., 1996,839. 3 M. Uemura, A. Daimon and Y. Hayashi, J. Chem. Soc., Chem. Commun., 1995, 1943. 4 G. B. Jones, B. J. Chapman, R. S. Huber and R. Beaty, Tetrahedron: Asymmetry, 1994,5, 1 199. 5 M. F. Semmelhack, in Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A. Stone and G. Wilkinson, Pergamon, Oxford, 1995, vol. 12, p. 979. 6 M. F. Semmelhack, in Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A. Stone and G. Wilkinson, Pergamon, Oxford, 1995, vol. 12, p. 1017. 7 C. F. Marcos, S. Perrio, A. M. Z. Slawin, S. E. Thomas and D. J. Williams, f.Chem. Soc., Chem. Commun., 1994,753. 8 M. E. Cain, M. B. Evans and D. F. Lee, f.Chem. Soc., 1962, 1694. 9 V. N. Ipatieff, H. Pines and B. S. Friedman, J.Am. Chem. Soc., 1938, 60,2731. 10 B. M. Trost and D. P. Curran, Tetrahedron Lett., 1981,22, 1287. I1 M. F. Semmelhack, H. T. Hall, M. Yoshifuji and G. Clark, J. Am. Chem. SOC.,1975,97, 1247. 12 T. A. Albright and B. K. Carpenter, Inorg. Chem., 1980,19,3092. 13 T. A. Albright, P. Hofmann and R. Hoffmann, J. Am. Chem. Soc., 1977,99,7546. 14 M. Iwao, T. Iihama, K. K. Mahalanab, H. Perrier and V. Snieckus, f.Org. Chem., 1989,54, 26. 15 (a)R.R. Fraser and T. S. Mansour, f.Organomet. Chem., 1986,310, C60; (b) P. M. Treichel and R. U. Kirss, Organometallics, 1987, 6, 249. 16 E. P. Kundig, V. Desobry, C. Grivet, B. Rudolph and S. Spichiger, Organometallics, 1987,6, 1 173. 17 D. A. Price, N. S. Simpkins, A. M. MacLeod and A. P. Watt, Tetrahedron Lett., 1994,35, 61 59. 18 S. G. Davies, T. Loveridge and J. M. Clough, J. Chem. Soc., Chem. Commun., 1995,817. 19 D. F. Shriver and M. A. Drezdzon, The Manipulation of Air Sensitive Compounds, Wiley, Chichester, 1986. 20 W. G. Kofron and L. M. Baclawski, J. Org. Chem., 1976,41, 1879. 21 SHELXTL PC, ver. 5.03, Siemens Analytical X-Ray Instruments, Madison, WI, 1994. Paper 6/04094B Received 11th June 1996 Accepted 29th July 1996 J. Chem. SOC.,Perkin Trans. I, 1996 2581
ISSN:1472-7781
DOI:10.1039/P19960002575
出版商:RSC
年代:1996
数据来源: RSC