Tris ketenimine

The oxime 299 is silylated in the presence of catalytic amounts of TMSOTf 20 to 300, which affords, via the Beckmann fragmentation intermediate 301 and alkylation with allyltrimethylsilane 82, 66% of the seco nitrile 302 [101, 102] (Scheme 4.39). Tris(trimethylsilyl) ketenimine 303 reacts with aldehydes such as benzaldehyde in the presence of Bp3-OEt2, via the aldol adduct 304, to give the unsaturated nitriles 305, in 99% yield, and HMDSO 7 [103]. 

The reaction of 4-(dichloromethylene)-2-phenyl-5(477)-oxazolone 400 and tri-phenylphosphine affords the vinylphosphonium salt 401, from which Al-benzoyl (triphenylphosphoranylidene)ketenimine 403 is obtained by hydrolytic ring opening of 401 and subsequent treatment of 402 with triethylamine (Scheme 7.129). 

Thermal cycloadditions of ketenimines to cait>onyl compounds requires activation of the 0=0 bond. The highly electrophilic bis(trifluoromethyl) ketone reacts at high temperature with diphenyl-N-to-lylketenimine (equation 73). Lanthanide shift reagents such as tris(6,6,7,7,8,8,8-heptafIuoro-2,2-di-methyl-3,S-octanedionato)-europium or -ytterbium [Eu(fod)3 or Yt(fod)a] are efficient catalysts for the cycloaddition of ketenimines with aldehydes (equation 74). The use of chiral catalysts such as tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato)-europium or -ytterbium [Eu(hfc)3 or Yt(hfc)3] has been found to generate only moderate enantiomeric excesses (20-40%). ... 

Bis(imino) thietanes, 343, 344, are prepared by reaction of isonitriles with iminothiiranes or of ketenimines with p-tolylsulfonyl isothiocyanate. Reaction of phosphonium ketimine ylides, for example, 312, and related compounds with isothiocyanates also gives bis(imino) thietanes, for example, 345. " Treatment of arylsulfonyl isothiocyanates with trimethylacetoisonitrile yields tris(imino)-thietanes, for example, 341. ... 

Kurtz and Shechter175 have found that the irradiation of 3,4,5-tri-phenylisoxazole in ether or benzene gives A-phenyl-benzoylphenyl-ketenimine (110, 40%), 3-benzoyl-2,3-diphenyl-1-azirine (111), and 2,4,5-triphenyloxazole ( 40%). 

N-Organosilyl Imines and Imides This group of compounds includes the organosilyl derivatives of ketenimines, ketimines, sulphodiimines, carbodiimides, iminophos-phoranes, etc. Tris(trimethylsilyl)ketenimine [380] (85% b.p. 65-70°C at 0.13 kPa = 1 mm Hg) is prepared from acetonitrile, r-butyllithium and chlorotrimeth-... 

Many methods exist for the synthesis of ( )-alk-2-enenitriles, of which Wittig and its modifications are the most widely used by contrast, few methods for the preparation of the (Z)-isomers are known. Sato and Niinomi have reported that aldehydes react with tris(trimethylsilyl)ketenimine (164) in the presence of boron trifluoride to give the adducts (165), which are converted into the (Z)-alk-2-enenitriles (166) by thermolysis followed by hydrolysis with a base. ... 

In contrast, the A -silylenamine (186) reacts in conventional fashion with acyl halides R COCl in the presence of KF to give (187), and in the same vein tris(trimethylsilyl)ketenimine when treated sequentially with an aldehyde and alkali gives (Z)-alk-2-enenitriles in good jdeld and high isomeric purity. A-Silylimines derived from non-enolizable aryl aldehydes and ketones give secondary or tertiary carbinamines respectively on reaction with organolithium compounds. ... 

When 4-azidophenols such as 89 (X = Y = Cl) were photolyzed in Nj matrices, azepin-4-ones (91) were the major products, presumably arising by tautomerization of the corresponding hydroxy-substituted cyclic ketenimines (90). In some cases, the ketenimine was observed directly in the IR spectra. Tautomerization to give the azepinones was favored in more concentrated matrices, suggesting that this process involved intermolecular proton transfer between pairs or aggregates of ketenimine molecules. Matrix photolysis of 4-azidophenols held out the promise of a synthetic route to the elusive azepin-4-ones under exceptionally mild conditions and was tried on preparative scales up to 50 mg or more in a specially constructed matrix-isolation ceU. Unfortunately, the azepinones did not survive warm-up at the end of the experiments, and only polymeric products were ultimately obtained. 

Carbonyl Condensations. Bis- or tris-TMS ketenimines condense with ketones, mediated by MgBr2, to produce an intermediate that loses hexamethylsiloxane, affording 2-alkenenitriles in high yield with high ( ) selectivity (eq 16). MgBr2 also enables the use of very mild bases like Triethylamine in Homer-Wadsworth-Emmons reactions, enabling the synthesis of unsaturated esters from aldehydes or ketones without the need for strongly basic conditions (eq 17). ... 

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