N-trimethylsilyl imine

N-silylated imines 509 react with the Li salts of tosylmethylisonitriles to give 4,5-disubstituted imidazoles in moderate yields [93]. Acetylation of N-trimethylsilyl imines 509 with acetyl chloride and triethylamine affords 72-80% of the aza-dienes 510 these undergo readily Diels-Alder reactions, e.g. with maleic anhydride at 24 °C to give 511 [94] or with dimethyl acetylenedicarboxylate to give dimethyl pyridine-3,4-dicarboxylates [94] (Scheme 5.29). 

Recent review articles on the synthesis and use of N-(trimethylsilyl)imines [104] or N-(trimethylstannyl)imines [105] focus primarily on the preparation of / -lactams. 

Sowohl N-Trimethylsilyl-imine von Aldehyden als auch Nitrile konnen mittels Niobium-Verbindungen zu vicinalen Diaminen gekuppelt werden. Die Silylamine setzt man mit... 

A simple preparation of electron-poor 2-azadienes and the preliminary study of their ability to participate in [4 + 2] cycloadditions was done almost simultaneously by out group (87CC1195) (Scheme 49). The preparation of 2-azadienes 212 with two appended methoxycarbonyl groups was achieved, in a multigram scale and in nearly quantitative yield, by the insertion reaction of N- trimethylsilyl imines 210 into the carbon—carbon triple bond of dimethyl acetylenedicarboxylate to give 211 followed by protodesilylation with CsF/MeOH. Azadienes 212 underwent at room temperature inverse-electron demand [4 + 2] cycloaddition with cyclic enamines to give exclusively exo-cycloadducts 213 in 82-95% yield. Acid hydrolysis of them resulted in their aromatization to yield 2-pyrindine (n = 1] and isoquinoline (n = 2) derivatives 214. 

Lactams.1 In the presence of Znl2 and t-butyl alcohol as a proton source, N-trimethylsilyl imines (1), prepared as shown, react with silyl ketene acetals (2)... 

While organometallic reagents condense with N-substituted imines (Schiff bases) to afford, after hydrolysis, good yields of substituted amines, the reaction with N-unsubstituted imines (203) derived from ammonia (which are easily hydrolyzed and self condense) is not synthetically useful. As a result, the use of masked imines containing labile silicon- or sulfur-Hiitrogen bonds, such as N-trimethylsilyl-imines (204) or N-sulfenimines (205), has been explored. 

The enantioselective asymmetric allylation of imines has been a synthetic challenge, the initial solutions of which required stoichiometric amounts of chiral allylbor on [87], allylsilane [88], allylzinc [89], or allylindium reagents [90]. Itsuno showed that a chiral B allyloxazaborolidine derived from norephedrine could add to the N trimethylsilyl imine prepared from benzaldehyde in high yield and enantiomeric excess (Scheme 1.22) [91]. Brown later reported that B allyldiisopinocamphenylbor ane is also very effective for the allylation of the same electrophiles, but the addition of a molar amount of water is necessary to obtain high yields [92]. The diastereo and... 

More recently, Georg et al. [23] have found that N -trimethylsilyl imines 11 of aromatic non-enolizable aldehydes and ketones, prepared by the methodology of Hart [24], can be converted to the corresponding IST-sulfonyl imines using aryl or alkyl sulfonyl chlorides (Scheme 5). Unfortunately, the procedure is not applicable to forming N-sulfonyl imines from enolizable aldehydes and ketones. 

Hydroxy-4-phenyl-P-lactams. The lithium enolate of (silyloxy)acetates (2) couple with the N-(trimethylsilyl)imine 3 to give 3-hydroxy-4-aryl- -lactams (4). The stereoselectivity depends in part on the size of the silyloxy group but mainly on the ester group. Use of either (+)- or (—)-/ra/w-2-phenyl-l-cyclohexyl (I) as the chiral auxiliary results entirely in a cw-/3-lactam (4) in 80% yield and 96-98% ee. Use of (-)-menthyl or of Oppolzer s D-isobornyl auxiliary (12,103-104) results in lower yields and enantioselectivity. The cyclocondensation with the ester 2 from (-)-l results in (3R,4S)-4 in 96% ee. On desilylation and acid hydrolysis, this lactam provides (2R,3S)-... 

As an alternative procedure to the reaction of N-trimethylsilyl-imines with ester enolates Colvin et al. have now reported that silyl ketene acetals can be employed in a one-pot synthesis of -... 

In conclusion, we have prepared, for the first time, chiral yV-aluminum- and N-trimethylsilyl imines starting from aldehydes and nitriles. These compounds represent interesting starting materials for the preparation of a variety of biologically active nitrogen containing compounds. 

Dirheniumheptoxide 2154 is converted by TCS 14, in the presence of 2,2 -dipyri-dine, into the dipyridine complex 2160 [77]. Free ReCls, NbCls, and WCI5 react with HMDSO 7 and 2,2 -bipyridine to form bipyridine oxochloride complexes 2161 and TCS 14, with reversal of the hitherto described reactions of metal oxides with TCS 14. The analogous Mo complex 2162 undergoes silylahon-amination by N-trimethylsilyl-tert-butylamine 2163 to give the bis-imine complex 2164 and HMDSO 7 [77] (Scheme 13.22). 

Addition of lithium bis(trimethylsilyl)amide to perfhiorinated ketones and solvolysis of the N-Si bond in methanol resulted the formation of stable, isolable N-H imine Z-E isomer mixtures along with a methanol adduct. Enantioselective reduction of these three-component mixtures with oxazaborolidine catalysts and catecholborane provided trifluoromethylated amines in 72-95% yields and 75-98% ee 267... 

Silylketene acetals react with imines under acidic conditions (Scheme 22). With N-alkylimines in the presence of a stoichiometric amount of TiCU, -lactams are formed in good yields. N-Aryl- " and N-trimethyl-silylimines also react under acidic conditions but yield only open-chain products. On the other hand, bis(trimethylsilyl)ketene acetals yield 3-lactams with both N-alkyl- and N-aryl-imines (Scheme 22). °... 

Type 4 and 5 alkyl complexes also catalyze the regioselective hydrogenation of acyclic imines (190 psi of H2, 90 °C, TOF = 0.40 h ) [147]. The stoichiometric reaction of A -benzylidene(trimethylsilyl)imine with 4(Sm CH(SiMc3)2) yielded a desilylated Cp 2Sm-imine-amido complex with a four-membered Sm(NSi-Me3)(CPh)N=CHPh chelate ring which converts further to Se-symmetric... 

The first example of enantioselective allylation of an azomethine function was reported in 1995 by Itsuno and co-workers [42a]. These researchers studied the addition of preformed chirally modified allylboranes to N -(trimethylsilyl)ben-zaldehyde imine (5a) (<2 g of imine, ca. 0.27 M). Of the wide range of chirally modified allylboron reagents reported in the literature, the use of chiral allylbo-ronates 42a-c and 5-allyldialkylborane 43 were logical first choices given their utility in the enantioselective addition to carbonyl substrates (Scheme 20). 

A Russian group has described two types of [2+2]-cycloadditions of N-sulfonyl imines. It was found that both ketene and trimethylsilyl ketene react with chloral-derived N-sulfonyl imine 233 to afford -lactams 234 in excellent yields [81] [Eq. (57)]. Although the compound produced from trimethylsilyl ketene appears to be a single isomer, the stereochemistry was not elucidated. 

The addition of N-(trimethylsilyl)benzophenone imine to 1,1-dimethyl-2,2-bis(trimethylsilyl)silene (54)243 proceeds in a fashion quite analogous to the reaction of benzophenone, but is much slower. Both the 2 + 2 (56) and the 4 + 2 (55) cycloadducts have been isolated (equation 74). The former is formed at only about half of the rate of the latter but dominates in the equilibrium. As described in Section III.A.2.C, the small amount of 54 present in the equilibrium can be trapped by other added reagents so that 56 represents a convenient means of storing the silene 54, which cannot be stored neat since it rapidly dimerizes244,246. Another such store is provided by the silenate adduct of 54 with NMe3, which reacts with N-(trimethylsilyl)benzophenone imine to yield 55 and 56266. 

The addition of N-phenylbenzophenone imine yields only the 4-l-2 adduct at first, but this can be thermally dissociated and eventually converted into the more stable 2-1-2 isomer244. Acetone ketazine also forms a 2-1-2 cycloadduct with 54244. No 2 + 4 adduct formation was observed. Bis(trimethylsilyl)diimide reacts with 54 to yield the 2 + 2 cycloadduct, a siladiazetidine which decomposes upon warming to 50 °C (equation 127)243. Azobenzene and PhN=NSiMe3 behave similarly244. 

The pyrolysis of [dimethoxy(methyl)silyl]bis(trimethylsilyl)amine350 yields products which can be ascribed to an initial formation of N-(trimethylsilyl)-methoxy(methyl)silanimine (equation 165). The isolated dimers may be formed by the imine dimerization or possibly by an attack of the silanimine on the precursor instead. Additional evidence for the presence of some of the intermediates postulated to account for the results was obtained by a study of the copyrolysis of [dimethoxy-(methyl)silyl]bis(trimethylsilyl)amine and hexamethylcyclotrisiloxane, which yielded a fairly complex mixture of products351. The formation of product 88 most likely proceeds through the unsaturated eight-membered ring silanimine 89 and not by way of meth-ylsilanitrile, although the latter possibility was also considered by the authors (equation 166). 

Colvin and his coworkers [86] reported that reaction of N-silyl imines with silyl ketene acetals in the presence of either Znl2 or trimethylsilyl triflate and t-butyl alcohol, followed by in situ treatment of the intermediate N-silyl p-aminoesters with MeMgBr, produced JV-silyl-azetidin-2-ones in good yields. Following this procedure (Scheme 30), starting from the silyl ketene acetal 179 and the N-silyl imine 180, the p-lactam 181 was produced in 44% yield as a... 

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