Imidoylstannanes, improved preparation and uses as acylanion equivalents

摘要

2283J. CHEM. SOC. PERKIN TRANS. I 1994 Imidoylstannanes, Improved Preparation and Uses as Acylanion Equivalents Bernard Jousseaume,a Nathalie Vilcot,a Alfredo Ricci and Edward R. T. Tiekink'j a Laboratoire de Chimie Organique et Organometallique, URA 35 CNRS, Universite Bordeaux I, 357, cows de la Liberation, 33405 Talence, France Department of Chemistry, The University of Adelaide, Adelaide, S.A. 5005 Australia An improved preparation of imidoylstannanes, by reaction of triorganostannyllithiums with imidoyl chlorides, is reported. This reaction is effective when phenyl or methyl groups are substituents on the tin atom, and when N-aryl C-alkyl or C-aryl imidoyl chlorides are used. After reaction with acyl chlorides, imidoylstannanes led to high yields of a-keto imines, which can be further hydrolysed into a-diketones.Transmetallation with organolithiums selectively gave the corresponding lithium reagents which showed a normal behaviour with alkyl halides, silicon halides, epoxides or chloroformates, leading to functional imines, hydrolysable to the corresponding ketones. This route forms a new entry to Walborski reagents. Acyl anion equivalents are versatile intermediates in synthetic organic reactions. They have been known for a long time as, for instance, acetylide anions that, after reaction and hydrolysis, can be converted into ketones,2 or nitronate anions which after addition to carbonyl compounds can be transformed into a carbonyl group.3 More recently, new acyl anion equivalents have been developed from the metallation of dithioacetals and vinyl derivatives,' and studies in this field continued apace.6 On the other hand, organotin compounds have proven to be important reagents in organic synthesis.The ease with which tin-carbon bonds are cleaved often allows the selective transfer of organic moieties from the metal to organic substrates.' This transfer can be performed after transmetallation with a lithium reagent from vinyl-,' all~l-,~ benzyl and a-hetero substi- tuted organostannanes, or under palladium catalysis. l2 The latter reaction broadened the scope of applications of organotins to carbonsarbon bond formation, since this mild method may be used in the presence of numerous functional groups.l2 Acylstannanes can be employed under catalysis, allowing an easy transfer of acyl groups to organic substrates such as acyl halide^.'^ Imidoylstannanes, known for a long time,14 and for which we recently proposed a new method of preparation,' ' have found only a limited number of applications.lh However, recent findings on the access to (silyliminomethy1)stannanes by the palladium-catalysed reac-tion of isocyanides with organo~ilylstannanes,~ and on their selective transmetallation with butyllithium,' * showed the potential of this class of compounds. In the same field, Walborsky earlier demonstrated the stability and usefulness of iminoyllithiums, prepared by addition of lithium reagents to isocyanides." Herein is reported an account of an improved synthesis of aryl imidoylstannanes by coupling triorgano- stannyllithiums with imidoyl chlorides, and of their reactivity towards acyl chlorides and organolithiums.Results and Discussion Imidoylstannanes were obtained in high yield by the coupling of imidoyl chlorides with triorganostannyllithiums. This route has previously been described to give imidoylstannanes in very low yield l4 and, with acyl chlorides, only impure acylstannanes 2o were obtained. With a careful control of the reaction temperature, however, and with the use of a bulky 2,6-xylyl group on nitrogen instead of a simple phenyl to improve stability towards oxygen, better results were obtained (Table 1). The stoichiometry of the reagents is also critical, since Table 1 Preparation of imidoyltriorganostannanes R' R2 Yield () Me Ph 86 Ph Ph 79 Me Me Me p-MeOC,H, Mep-ClC,H, 69 72 68 Bu Me 16" Me Et 67 Me Bur 69 a Estimated yield by 19Sn NMR.unchanged imidoyl chloride reacts with the imidoylstannane formed at room temperature, and thus lowers the yield of the reaction. R2 R2 AN=;( + R'amp;nLi -,B"cMF Ad=( CI SnR13 Ar = 2,6-Me,C,H3 The reaction is general enough to tolerate alkyl (Me, Et, Bur) and aryl (Ph, p-MeOCamp;,, p-CIC,H,) groups on the imidoyl carbon. On the tin atom, methyl and phenyl groups were successfully used. With tributylstannyllithium, the imidoyl- stannane was recovered in low yield, together with aldimine, which suggests a single electron-transfer process leading to reductiom2 Imidoylstannanes are characterized by their '3C NMR spectra having a signal for the imine carbon around 190 ppm with a 1J('3C-1'9Sn) in the range 200-280 Hz.With methyl groups on the tin atom, the I9Sn NMR resonance lies in the range -80 to -90 ppm; this is the same region as for acylstannanes.*' NMR data indicate that only one isomer was formed during the reaction. Since imidoyl chlorides exist in the 2 configuration22 and, further, since the coupling of lithium reagents with vinylic species usually occurs stereo~pecifically,~~ it was reasonable to assign the Z configuration to the imidoylstannanes. A 2D NOESY experiment conducted on 4-chloro-a-(2,6-xylylimino)benzyltrimethylstannane showed a clear correlation between the trimethylstannyl hydrogens and the methyl hydrogens of the xylyl group.No correlation was observed between ortho hydrogen of the 4-chlorobenzyl group and methyl hydrogens of the xylyl group. An independently reported NOE experiment on butyliminoethyl(tributy1)- c(35) yi!?C(34) Fig. 1 ORTEP38 view of 2,6-Me2C6H4NC(SnPh,)Ph with thermal ellipsoids at the 20 probability level. Selected interatomic bond lengths (A) and angles Sn-C(1), 2.178(5); Sn-C(l l), 2.121(6);(O): Sn-C(21), 2.1 19(6); Sn-C(3 l), 2.122(6);C( 1)-N( l), 1.272(7);C( 1kC(41), 1.484(8); N( I)-C(51), 1.41 4(8); C( 1 )-Sn-C( I l), 107.7(2); C( 1 )-Sn-C(21), 117.7(2); C(1)-Sn-C(31), 110.3(2); C(l 1)-Sn-C(21), 108.8(2); C(11)- Sn-C(31), 107.5(2); C(21)-Sn-C(31), 104.5(2); Sn-C(1)-N(I), 122.8(4); Sn-C(l)-C(41), 119.4(4); N(1)-C(1 jC(41), 117.8(5); C(l)-N(ljC(51), 123.4(5).Table 2 Reaction of imidoylstannanes with acyl chlorides Keto imine a-Diketone R2 R3 yield () yield () Ph Ph Ph Ph Ph Ph p-ClC,H, Me Ph stannane led to the same conclu~ion.~~ Nevertheless, a crystal structure determination was conducted on ~r-(2,6-xylyl-imino)benzyl(triphenyl)stannane (Fig. 1). It revealed a Z configuration which confirmed the NOESY studies. There were no significant intermolecular contacts; the closest non- hydrogen contact occurs between C(35) and C(35') 3.41(1) A. In the molecule, the tin atom exists in a distorted tetrahedral geometry with the C-Sn-angles lying in the relatively narrow range of 104.5(2)-117.7(2)"; the greatest deviation from the ideal tetrahedral angle is found for C( 1)-Sn-C(21).Reflecting the disparate organic groups, the Sn-C bond distances fall into two classes, i.e. the Sn--C(Ph) distances lie in the range 2.119(6)- 2.122(6) A, in contrast to the Sn-C(1) bond which is significantly longer at 2.178(5) A, in the range of tin-vinyl bonds.25 The C(1)-N(1) bond distance of 1.272(7) A is consistent with significant double bond character and the angles subtended by the donor atoms at both the C(l) and N(l) are indicative of sp2 centres. The Sn, N(l), C(1), C(41) and C(51) atoms lie 0.000(4), 0.035(6), 0.016(6), -0.024(6) and -0.046(7) A, respectively, out of the least-squares plane through these atoms.The PhC=NC,H,Me, ligand is not planar, however, as shown in the torsion angles of 6.6(9) and -89.0(8)" for C(42)/C(41)/C( 1)/N( 1) and C(52)/C(5l)/N(l)/C( l), respectively. The imidoylstannanes were then treated with acyl chlorides J. CHEM. SOC. PERKIN TRANS. 1 1994 under palladium catalysis, to give keto imines as previously described for acylstannanes.I3 In fact, they were much more reactive than acylstannanes, since a palladium catalyst, heating and long contact time were unnecessary to achieve the reaction. Indeed, the coupling occurred very rapidly at room tem-perature, leading to the desired products in good yield. These were purified by column chromatography on alumina, without hydrolysis of the imine moiety or by distillation.The reaction was very effective when aromatic imidoylstannanes and aromatic acyl chlorides were used (Table 2). With either aliphatic imidoylstannanes and aromatic acyl chlorides, or with aromatic imidoylstannanes and aliphatic acyl chlorides, the coupling failed, and only degradation products were recovered. Aliphatic acyl chlorides were also found unsuitable in the coupling with acylstannanes. l3 Keto imines, which can be considered as monoprotected 1,2-diketone~,~,cannot be obtained from unsymmetrical a-diketones since the mono-imination of a-dicarbonylated compounds is only selective with well-differentiated groups around the carbonyls, such as in 1 -phenylpropane- 1,2-dione or phenylglyoxal. 27 After hydrolysis, 172-diketones can be recovered in high yield.R2 200c+ R3COCI Et20Ad=( SnMe3 ArNq I? 0 When treated with methyllithium, at -78 "C in THF, aromatic imidoylstannanes underwent clean transmetallation, leading to the corresponding iminoyllithiums. The reaction was very selective since no addition to the azomethine linkage was observed; this contrasts to what happens with acylstannanes. The imidoyllithium having R = Ph was characterized by treatment with deuterium oxide, which led to N-2Hbenzyl- idene-2,6-xylylamine containing 95 deuterium incorpor- ation. This method turns out to be a good way to prepare this class of lithium reagent, since addition of aryllithiums to isocyanides gives less good yields of the corresponding imidoyllithiums than aliphatic lithium compounds, l9 and since transmetallation of (silyliminomethy1)stannanes does not allow an access to aromatic imidoyllithiums.* R2 MeLi, THF. -78 "C -ArNd R2 A~N=( (-Me,Sn)SnMe, Li Ar = 2,6-Me,C6H3 When the same transmetallation was attempted with 1-(2,6- xylylimino)ethyl(trimethyl)stannane and methyllithium, fol-lowed by alkylation with ethyl bromide, the coupling product was isolated in only 39 yield, together with 1-(2,6-xyIyl-imino)butane (25) and 3-(2,6-~ylylimino)hexane(873, indi-cating that lithiation occurred also on the methyl to the azomethine. The reactivity of the aromatic imidoyllithiums was then probed with alkyl halides, silicon halides, benzaldehyde and isobutyl chloroformate (Table 3).The corresponding products were isolated in high yield, indicating a normal behaviour of R2 R2 ArN==( ArN=( HDIH -o=(R2 Li E E Ar = 2,6-Meamp;H3 J. CHEM. SOC. PERKIN TRANS. 1 1994 2285 Table 3 Reactions of imidoyllithiums with selected electrophiles Imine 2,6-Me2C6H,N=CR'R2 Aldehyde or ketone R2 EX ( yield) ( yield) Ph Ph Ph Ph Ph Ph Ph Ph p-CIC6H4 H2O D2O Me1 EtBr EtBr Me3SiC1 Bu'Me,SiCl PhCHO CICOOBu' R' = H,R2 = Ph(98) R' = D,R2 = Ph(97) R' = Et, R2 = Ph (86) R' = Et, R2 = p-CIC6H4 (82) R' = SiMe,, R2 = Ph (82) R' = SiMe2Bu',R2 = Ph(88) R' = C(OH)Ph,R2 = Ph(87) R' = COZBui, R2 = Ph (65) R' = Me, R2 = Ph (85) PhCHO (95) PhCDO (95) PhCOMe (81) PhCOEt (84) p-ClC,H,COEt (78) PhCOSi(Me,)Bu' (81) PhCOCH(0H)Ph (82) PhCOC0,Bu' (60) Table4 Crystallographic data for a-(2,6-~ylylimino)benzyl(triphenyl)-stannane Formula C33H29NSn Crystal size (mm) 0.23 x 0.23 x 0.40 Crystal system Monoclinic Space group 4 1 6.51O( 2)p21 In WA 9.036(3) CIA 1 8.896( 2) PI" 110.58(1) VIA3 2638.9(7) z 4 PcIg cm F(000) 1.405 1136 p/cm-' 9.89 Transmission coefficients 0.948-1.058 Data collected -h, +k, fl No.of data collected 6922 No. of unique data 670 1 Ra 0.049 No. of unique data with I b 30(I) 460 1 R 0.032 Residual density (e A-3)Rw 0.057 0.39 these lithium compounds. Alkylation was effective both with iodides (85) and bromides (82), when, in contrast, imidoyllithium prepared from (butylimino)propyltributyl-stannane failed to give the expected coupling products with organic halides.24 Trimethylchlorosilane and tert-butyl-(dimethy1)chlorosilane led into the corresponding iminoyl- silanes, which could be hydrolysed to acylsilanes.With benzaldehyde, the desired a-hydroxy imine was obtained (87), and hydrolysed to give the corresponding a-hydroxy ketone (81). It is noteworthy that the recently reported samarium- mediated coupling of organic halides, isocyanide and carbonyl compounds, very effective with alkyl halides, does not allow the preparation of aryl-substituted a-hydroxy imines.28 Isobutyl chloroformate gave the desired a-imino ester (65), which, in turn, led to the corresponding a-keto ester (60), after hydrolysis.Thus, the present procedure broadens the synthetic utilities of organostannanes. It provides a valuable access to imidoyl- stannanes and demonstrates their synthetic applications for carbon4arbon bond formation either by direct reaction with acyl chlorides, or after transmetallation with lithium reagents. Experimental All reactions were carried out under a nitrogen atmosphere. THF and diethyl ether were distilled from sodium benzo- phenone ketyl prior to use. Pentane and light petroleum were distilled from calcium hydride. Imidoyl chlorides were obtained from the reaction of the corresponding amides with phosphorus pentachloride. 'O Tributylstannyllithium 30 was prepared by deprotonation of tributylstannane. Lithium tri- phenyl- and trimethyl-stannates were prepared by cleavage of the corresponding hexaorganodistannane ,' by lithium in THF.The tin reagents were used immediately after preparation. 'H and 13C NMR spectra were recorded on a Bruker WH 250 (internal reference Me,Si). "Sn NMR spectra were recorded on a Bruker AC 200 (internal reference Me,Sn). J Values are given in Hz. Crystallography.-Intensity data were measured (0-28 scan technique, room temperature) on a Rigaku AFC6R diffract- ometer using graphite-monochromatized Mo-Ka radiation, A = 0.710 73 A, up to a maximum Bragg angle of 27.5'. The data set was corrected for Lorentz and polarization effects32 and an empirical absorption correction was applied. The structure was solved by direct-methods34 and refined by a full-matrix least-squares procedure based on F'.Non-H atoms were refined with anisotropic thermal parameters and H atoms were included in the model at their calculated positions. Unit weights were employed in the refinement. The teXsan software package,32 installed on an Iris Indigo workstation, was employed for data manipulation. For details of the crystal data see Table 4. Tables of atomic coordinates, bond lengths and angles, and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre.* Procedure for Preparation of Imidoy1stannanes.-To a solution of imidoyl chloride (20 mmol) in THF (30 cm3) at -78 'C were slowly added a triorganostannyllithium solution (20 mmol) via a cannula.The solution was stirred at -78 "C for 1 h and at ambient temperature for 1 h and was then evaporated. The residue was extracted with pentane (100 cm3) and the extract then evaporated. The product was isolated by liquid chromatography on a deactivated (6 H,O) alumina column using light petroleum as eluent. Alternatively, trimethylstannylated compounds can be distilled in a Kugel- rohr apparatus. a-(2,6-Xylylimino)benzylidene(trimethyl)-stannane: 86; m.p. 48 "C; 6,(250 MHz; CDCl,) 0.12 (9 H, s, 2JSn,H53), 2.25 (6 H, s) and 7.0-7.8 (8 H, m); 6,(62.9 MHz; CDCl,) -6.9('JSn,c320), 18.3,123.5, 127.1,128.0, 128.5, 129.5, 143.9(2Jsn,c107), 152.1 (3Jsn,c52); 162.5 and 190.9 ('Jsn,c317); 6,,(74.5 MHz; C,D,) -76.1; Found (FABHRMS): 374.0904.Calc. for C,~H,,NSI'I: m/z 374.09313. a-(2,6-Xylylimino)-benzylidene(tripheny1)stannane: 79; m.p. 94 'C;6,(250 MHz; CDCl,) 2.21 (6 H, s), 6.75 (3 H, m), 7.40 (18 H, m) and 8.15 (2 H, m); 6,(62.9 MHz; CDCl,) 18.7, 124.7, 125.7, 128.2, 128.6 (2Jsn,c51),128.9,130.5, 137.0(3Jsn,c39), 139.4, 143.5, 151.8and 186.3 ('Jsn,c297); 6,,(74.5 MHz; C,D,) -184.6 Found * For details of the scheme see 'Instructions for Authors (1994)', J. Chem. Soc., Perkin Trans. I, 1994, Issue 1. (FABHRMS): 560.1377. Calc. for C,,H,,NSn: m/z 560.14001. 4-Methoxy-a-(2,6-xylylimino)benzylidene(trimethyl)stannane: 69; b.p. 155 "C ( lo4 Torr); 6,(250 MHz; CDCl,) 0.01 (9 H, s, ,JSn,, 51), 2.08 (6 H, s), 3.49 (3 H, s), 6.9 (5 H, m) and 7.8 (2 H, m); 6,(62.9 MHz; CDCl,) -6.9 (lJsn,c316), 18.4, 54.9; 114.1, 123.3,128.1,129.1,130.1,131.7,136.5,162and191.5(1Jsn,c312); 6,,(74.5 MHz; C6D6) -79.6; Found (FABHRMS): 404.1000.Calc. for C, 9H26NOSn: m/z 404.10361. 4-Chloro-a-(2,6- xylylimino)benzylidene(trimethyl)stannane: 72; m.p. 94 "C; b.p. 160 "C Torr); 6,(250 MHz; CDCl,) -0.01 (9 H, s, ,JSn,, 51), 2.08 (6 H, s) and 6.9-7.8 (7 H, m); 6,(62.9 MHz; CDCI,) -7.1 ('Jsn,,-319), 18.4,123.6,128.2,128.7, 128.8, 135.6, 142.1 (2Jsn,c112), 152.3 50); 160.9 and 188.0 (lJsn,c308); d~~(74.5MHZ; C6D6) -74.8 Found (FABHRMS): 408.0539. Calc. for C,,H,,ClNSn: m/z 408.05411. Trimethyl1-(2,6- xylylimino)ethylstannane: 68; b.p. 130 "C ( Torr); 6,(250 MHz;CDCl,) -0.15(9H,~,~J,,,,55), 1.94(6H,s),2.35(3H,s, ,JSn,H 28) and 6.7-6.9 (3 H, m); dc(62.9 MHz; CDC1,) -8.7 ('.Isn,,-316), 18.3, 31.8 (2Jsn,c137), 123.4, 128.1, 128.4, 152.4 (,Jsn,c 60) and 191.6 ('Js,,~313); d~~(74.5 MHZ; C6D6) -81.8 Found: (HRMS): 31 1.0691. Calc.for C,,H,,NSn: m/z 3 1 1.06961. Tributylc1-(2,6-~ylylimino)ethylstannane: 16; b.p. 160 "C (10-4Torr);6H(250 MHz; CDCl,) 0.7-1.6(27 H, m), 2.05(6H,s),2.46(3H,s,3Js,,,26)and6.8-7.0(3H,m);6c(62.9 J. CHEM. SOC. PERKIN TRANS. 1 1994 m.p. 98 "C (Found: C, 75.72; H, 4.94; N, 3.87. Calc. for C,,H,,ClNO: C, 75.97; H, 5.22; N, 4.03); 6,(250 MHz; CDCl,) 2.05 (6 H, s) and 6.6-7.9 (12 H, m); 6,(62.9 MHz; CDCl,) 18.8,124.3,127.7,128.0,128.2,128.3,128.4,129.0,129.2, 130.4,132.0, 133.3,135.4,166.7 and 195.9. 1-(4-Nitropheny1)-2- phenyl-2-(2,6-xylylimino)ethanone:46; m.p.1 18 "C (Found: C, 74.2; H, 5.3;N, 7.4. Calc. for C,,H,,N,O,: C, 73.73; H, 5.06; N, 7.82); 6,(250 MHz; CDCl,) 2.08 (6 H, s) and 6.4-8.2 (12 H, m);6,-(62.9 MHz; CDCl,) 18.4,118.0,123.7, 124.3,127.9,128.0, 129.2,129.3,132.3,134,139.3,146.6,150.5,165.9and196.3.1-(1-Naphthyl)-2-phenyl-2-(2,6-xylylimino)ethanone:72 (Found: C,85.8; H,6.0;N,3.6.Cak.fOrC26H21NO:C,85.92;H,5.82;N, 3.85);6,(250 MHz; CDC1,) 2.13 (6 H, s) and 6.5-8.6 (15 H, m); 6,(62.9 MHz; CDCl,) 18.7, 123.7, 124.2, 125.9, 126.8, 128.1, 128.3, 128.5, 128.7, 129.2, 130.6, 131.7, 134.1, 135.9, 147.5, 167.8 and 199.4. 2-(4-Chlorophenyl)- 1-(4-methoxyphenyl)-2-(2,6-~ylylimino)ethanone:74 (Found: C, 72.6; H, 4.95; N, 4.0. Calc. for C,,H,,ClNO,: C, 73.1 1; H, 5.33; N, 3.71); 6,(250 MHz; CDCl,) 2.25 (6 H, s), 3.13 (3 H, s) and 6.4-7.9 (1 1 H, m); 6,(62.9 MHz; CDCl,) 18.6, 54.7, 113.8, 123.9, 127.4, 127.8, 127.9, 128.2, 129.2, 129.4, 131.4, 134.1, 137.7, 147.5, 166.0 and 194.2.Procedure for the Preparation of Diketones.-A solution of MHz;CDCl,) 10.2('JSn,,-307), 13.6, 18.3,27.3(2Jsn,c60),29.3,keto imine (5 mmol) in a mixture of THF (20 cm3) and HCl(3 32.7 (2Jsn,c112), 123.4, 127.8, 128.0, 152.4 (,JSn,,-50) and 192.8 ('Jsn,,-312); 6sn(74.5 MHZ; C6D6) -85.6; Found (HRMS): 437.2197. Calc. for C,,H,,NSn; m/z 437.21041. Trimethylcl- (2,6-xylylimino)propylstannane:67; b.p. 135 "C ( lo4 Torr); 6,(250 MHz; CDCl,) -0.13 (9 H, s, ,JSn,, 53, 1.17 (3 H, t), 1.96 (6 H, s), 2.63 (2 H, q, ,JSn,, 24) and 6.8-7.0 (3 H, m); dc(62.9 MHz; CDCl,) -8.4 ('Jsn,c312), 10.8, 18.0, 38.0 (,JSn,c 123), 123.1, 126.0,127.9, 151.9 (3Jsn,c49) and 195.0 ('JSn,,-302); 6sn(74.5 MHz; C6D6) -81.3; Found (HRMS): 325.0858.Calc. for C,,H,,NSn: m/z 325.08521. 2,2-Dimethyl-l-(2,6- xyly1imino)ethyll trimethylstannane: 69; b.p. 140 "C (1OP4 Torr); 6,(250 MHz; CDC1,) 0.03 (9 H, s, 2JSn,H56), 1.33 (9 H, s), 2.07 (6 H, s) and 6.8-7.0 (3 H, m); 6,(62.9 MHz; CDCl,) 6 -5.1 ('Jsn,,304), 18.2,28.1,45.0(2Js,,,117),123.0,125.6,128.0, 150.7 (,JSn,c59) and 197.9 ('Jsn,c301); 6,,(74.5 MHZ; C6D6) -89.0; Found (HRMS): 353.1 154. Calc. for C,,H,,NSn: m/z 353.1 1651. Procedure for the Preparation of Keto 1mine.s.-In a Schlenk tube containing a solution of imidoylstannane (10 mmol) in diethyl ether (10 cm3) at room temperature, was added dropwise acyl chloride (10 mmol).After the mixture had been stirred for 15 min, it was evaporated and the residue chromatographed on silica gel (eluent light petroleum-diethyl ether 95 : 5). The crystalline keto imines were recrystallized from toluene-light petroleum (50 : 50). 1,2-Dipheny1(2,6-xylylimino)-ethanone: 80; m.p. 108 "C (Found: C, 84.7; H, 5.7; N, 4.15. Calc. for C,,H,,NO: C, 84.32; H, 6.1 1; N, 4.47);6,(250 MHz; CDC1,) 2.12 (6 H, s) and 6.7-8.0 (12 H, m); 6,(62.9 MHz; mol dm-,; 10 cm3) was stirred for 15 h at room temperature. The mixture was extracted with ether (2 x 30 cm3), and the combined extracts were dried, filtered and evaporated. The product was then purified by column chromatography on silica (eluent: light petroleum4iethyl ether, 90 : 10).Benzil, 76; m.p. 95 "C. 2-(4-Methoxyphenyl)-l -phenylethanedione: 73; m.p. 53 "C(lit.,35 52 "C); 6,(250 MHz; CDCl,) 3.1 (3 H, s) and 7.0- 7.9 (9 H, m); 6,(62.9 MHz; CDCl,) 54.6, 113.8, 126.5, 128.0, 128.4, 131.9, 136.7, 192.9 and 193.6. 2-(3-Methoxyphenyl)-l- phenylethanedione: 69; m.p. 92 "C; 6,(250 MHz; CDCl,) 3.61 (3 H, s) and 7.0-7.8 (9 H, m); 6,-(62.9 MHz; CDCl,) 55.4, 113.1, 121.7,123.1,129.1,129.8,130.1,132.9,134.2,134.9,160.1, 193.9 and 194.6 (Found: C, 74.4; H, 5.4. Calc. for Cl,Hl2O3: C, 74.99; H, 5.03). 2-(4-Chorophenyl)- 1-phenylethanedione: 68, m.p. 76 "C (lit.,35 75 "C); 6,(250 MHz; CDCI,) 7.1-7.9 (9 H, m); 6,-(62.9 MHz; CDCl,) 129.1, 129.4, 129.9, 131.2, 131.3, 132.8, 135.1, 141.5, 193.0 and 193.8.2-(4-Nitrophenyl)-l-phenyl-ethanedione: 40; m.p. 138 "C (lit.,36 139 "C); 6,(250 MHz; CDCl,) 7.0-8.2 (8 H, m); 6,-(62.9 MHz; CDCl,) 118.2, 124.6, 129.0, 132.1, 134.2, 139.6, 146.1, 150.2, 192.8 and 193.3. 2-(1- Naphthy1)-1-phenylethanedione: 67; m.p. 97 "C (lit.,,, 97 "C); 6,(250 MHz; CDCl,) 6.8-8.0 (1 1 H, m) and 9.55 (1 H, d); 6,(62.9 MHz; CDCl,) 124.6, 127.2, 127.7, 128.1, 128.4, 129.0, 129.2, 129.6, 130.1, 134.5, 135.2, 135.8, 194.6 and 197.5. 1-(4-Chlorophenyl)-2-(4-methoxyphenyl)ethanedione: 68; m.p. 127 "C (lit.,36 128 "C); 6,(250 MHz; CDCl,) 4.1 (3 H, s) and 6.9-8.0 (8 H, m); 6,-(62.9 MHz; CDCl,) 61.0, 120.0, 130.2, 134.8, 136.4, 136.5, 137.4, 145.6, 170.2, 197.7and 198.9.CDCl,) 18.8,124.1,127.7,128.1,128.3,128.5,128.8,129.0,129.2, Transmetallation of Imidoy1stannanes.-To a solution of 131.9,133.9,135.2,135.7,167.3and 197.1.1-(4-Methoxyphenyl)-imidoylstannane (10 mmol) in THF (20 cm3) at -78 "C, was 79; m.p. 132 "C (Found: added dropwise methyllithium in diethyl ether (1.6 mol dm-,; 10 2-phenyl-2-(2,6-xylylimino)ethanone: mmol). After 15 min, the electrophile (1 1 mmol) in THF (10 C,80.2;H,5.75;N,3.8.Calc.forC,3H,,NO,:C,80.44;H,6.16; N, 4.08); 6,(250 MHz; CDCl,) 2.22 (6 H, s), 3.05 (3 H, s) and cm3) was also added to the mixture and the whole was then stirred for 1 h at room temperature. After this it was hydrolysed 6.3-8.1(12H,m);6c(62.9MHz;CDC1,)18.9,54.9,114.0,123.9, and extracted with diethyl ether (2 x 50 cm3). The solvents 126.6,127.7,128.0,128.1,128.3,128.4,128.8,129.1,131.8,136.0, 167.4 and 194.9.1-(3-Methoxyphenyl)-2-phenyl-2-(2,6-xylyl-imino)ethanone: 78 (Found: C, 80.05;H, 5.7; N, 3.8. Calc. for C,,H,,NO,: C, 80.44;H, 6.16; N, 4.08);6,(250 MHz; CDCl,) 2.09 (6 H, s), 2.94 (3 H, s) and 6.8-7.9 (12 H, m);dC(62.9 MHz; CDCl,) 18.8,54.7,112.1, 121.2, 122.6, 124.1,127.7, 128.2, 128.3, 129.2, 129.6, 131.9, 135.8, 136.4, 147.8, 160.2, 167.2 and 196.9. 1-(4-Chlorophenyl)-2-phenyl-2-(2,6-xylylimino)ethanone:77; were evaporated and the products were purified by distillation (Kugelrohr apparatus). N-Benzylidene-2,6-xylylamine:91; b.p. 100 "C (0.05 Torr) (Found: C, 85.4; H, 7.6; N, 6.3. Calc. for C,,H,,N: C, 86.08; H, 7.22; N, 6.69); 6,(250 MHz; CDCl,) 2.14 (6 H, s), 6.9-7.8 (8 H, m) and 8.15 (1 H, s); 6,-(62.9 MHz; CDCI,) 18.3,124.3,127.6,128.6,129.0,129.3,132.0,136.6,151.7 and 162.6.N-(2HBenzylidene)-2,6-xylylamine: 93; b.p. J. CHEM. SOC. PERKIN TRANS. 1 1994 100 "C (0.05 Torr); 6,(250 MHz; CDCI,) 2.14 (6 H, s) and 6.9-7.9(8H,m);6,(62.9MHz;CDC13)18.7,124.1,127.3,128.5, 128.8, 129.1, 131.8, 136.4, 151.7 and 162.8 (t, 'JC,,24). N-(l- Phenylethylidene)-2,6-~yIylamine:85; b.p. 120 "C (0.05 Torr) (Found: C, 85.4; H, 8.1; N, 5.8. Calc. for C,,H,,N: C, 86.06; H, 7.67; N, 6.27); 6,(250 MHz; CDCI,) 2.1 (6 H, s), 2.2 (3 H, s), 7.1-8.3 (8 H, m);6,(62.9 MHz; CDCI,) 17.6, 18.2, 123.0, 125.8, 127.3, 128.1, 128.6, 129.0, 130.5, 139.3 and 162.7.N-(l- Phenylpropylidene)-2,6-~ylylamine:86; b.p. 130 "C (0.05 Torr) (Found: C, 85.5; H, 7.8; N, 5.5. Calc. for C1,H19N: C, 86.03; H, 8.07; N, 5.90);6,(250 MHz;CDC1,) 1.03 (3 H, t), 2.17 (6 H, s), 2.56 (2 H, q) and 7.0-8.1 (8 H, m);6,(62.9 MHz; CDCl,) 11.7, 18.5, 24.1, 123.0, 125.8, 127.9, 128.2, 128.8, 130.6, 138.2, 149.1 and 170.5. N- 1-(4-Chlorophenyl)propylidene-2,6-xylyl-amine: 82; b.p. 140 OC (0.05)(Found: C, 75.7; H, 6.35; N, 4.8. Calc. for C, 7H1 ,ClN: C, 75.17; H, 6.68; N, 5.15); 6,(250 MHz; CDC13)1.08(2H,t),2.21(6H,s),2.59(3H,q)and7.0-8.1(7H, m);6,(62.9 MHz; CDCl,) 11.6, 18.4, 23.8, 123.1, 125.5, 128.2, 128.9,129.2,136.3,136.6,148.8and 169.1. Trimethyl(2,6-xylyl- imino)benzylsilane: 82; b.p. 130 "C (0.05 Torr) (Found: C, 76.2; H, 7.7; N, 5.2.Calc. for C,,H,,NSi: C, 76.81; H, 8.24; N, 4.98); 6,(250 MHz; CDCI,) 0.40 (9 H, s), 2.03 (6 H, s), and 6.8-7.9 (8 H, m); 6,(62.9 MHz; CDC1,) -0.9, 18.6, 122.9, 125.7, 127.8, 128.3, 129.1, 129.9, 130.3 and 131.6. tert-But yl (dimet h yl )a-(2,6-xylylimino) benzy1)silane: 8 8; b.p. 145 "C (0.05 Torr) (Found: C, 78.4; H, 8.7; N, 4.8. Calc. for C,,H,,NSi: C, 77.96; H, 9.03; N, 4.33);6,(250 MHz; CDCI,) 0.44 (6 H, s), 1.20 (9 H, s), 2.17 (6 H, s) and 6.9-7.2 (8 H, m); dc(62.9 MHz; CDCl,) -4.7, 19.0, 27.2, 122.2, 124.7, 125.6, 127.7, 127.9, 128.0, 141.8, 150.9 and 188.3. 1,2-Diphenyl-2-(2,6- xyly1imino)ethanol: 87; b.p. 180 "C (0.01 Torr) (Found: C, 83.5; H, 6.6; N, 4.75. Calc. for C,,H,,NO: C, 83.78; H, 6.71; N, 4.44); 6,(250 MHz; CDCl,) 2.26 (6 H, s), 4.92 (1 H, s), 5.93 (1 H, s) and 6.8-7.9 (13 H, m); 6,(62.9 MHz; CDCI,) 19.4, 65.7, 122.1, 127.9, 128.1, 128.8, 128.9, 129.0, 129.1, 129.4, 133.6, 135.4, 138.6, 144.2 and 198.7.Isobutyl 2-phenyl-2-(2,6- xy1ylimino)acetate: 65; b.p. 150 "C (0.05 Torr) (Found: C, 78.1; H, 7.0; N, 4.8. Calc. for C,,H,,NO,: C, 77.64; H, 7.49; N, 4.53); 6,(250 MHz; CDCl,) 0.97 (6 H, d), 2.00 (1 H, m), 2.12 (6 H, s), 4.15 (2 H, d) and 6.9-8.0 (8 H, m); 6,(62.9 MHz; CDCI,) 19.0,27.7,71.9, 124.3, 127.8, 128.6, 129.3, 128.9, 129.9, 132.5, 134.9, 164.1 and 170.0. Hydrolysis of Imines.-A solution of imine (5 mmol) in a mixture of THF (20 cm3) and HCl (10 cm3; 3 mol drn-,) was stirred for 15 h at room temperature and then extracted with ether (2 x 30 cm3).The combined extracts were dried, filtered and evaporated. The product was then purified by column chromatography on silica (eluent: petroleum-diethyl ether, 90 : 10). Their characteristics were found identical with those of authentic materials. Acknowledgements The Australian Research Council is thanked for support of the crystallographic facility. We are indebted to Schering-France Company for a gift of organotins. References 1 For comprehensive reviews see: 0.W. Lever, Tetrahedron, 1976,32, 1943. D. J. Ager, in Umpoled Synthons: A Survey of Sources and Uses in Synthesis, ed. T. A. Hase, Wiley, New York, 1987. 2 V. Jager and H. G. Viehe, Methoden der Organischen Chemie, 4th edn., vol.V/2a, 1977. 3 S. F. Martin, Synthesis, 1979, 633. 4 B. T. Grobel and D. Seebach, Synthesis, 1977,357. 5 J. E. 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