Glyoxylates aldimines

Table 9 1,3-Asymmetric Induction in the Addition of Allyl Organometallic Reagents (37) to Glyoxylate Aldimines (36) Derived from Chiral Amines (Equation 9) - ...

Except for the well-documented conjugate additions of diethylaluminum cyanide,92 triethylaluminum-hydrogen cyanide and Lewis acid-tertiary alkyl isonitriles,93 examples of Lewis acid catalyzed conjugate additions of acyl anion equivalents are scant Notable examples are additions of copper aldimines (233),94, 94b prepared from (232), and silyl ketene acetals (234)940 to a,(3-enones which afford 1,4-ketoal-dehydes (235) and 2,5-diketo esters (236), respectively (Scheme 37). The acetal (234) is considered a glyoxylate ester anion equivalent. 

Some bifunctional 6 -OH Cinchona alkaloid derivatives catalyse the enantioselective hydroxyalkylation of indoles by aldehydes and a-keto esters.44 Indole, for example, can react with ethyl glyoxylate to give mainly (39) in 93% ee. The enan- tioselective reaction of indoles with iV-sulfonyl aldimines [e.g. (40)] is catalysed by the Cu(OTf)2 complex of (S)-benzylbisoxazoline (37b) to form 3-indolylmethanamine derivatives, in up to 96% ee [e.g. (41a)] 45 Some 9-thiourea Cinchona alkaloids have been found to catalyse the formation of 3-indolylmethanamines [e.g. (41b)] from indoles and /V-PhS02-phenyli mines in 90% ee.46 Aryl- and alkyl-imines also give enantioselective reactions. 

Whiting et al. [20] found the catalytic system for an aza Diels-Alder reaction by the use of a combinatorial approach to catalyst selection. When methyl glyoxylate-derived aldimine 25 was reacted with Danishefsky s diene 24 in the presence of the chiral magnesium catalyst (10 mol %), prepared in-situ from chiral diphenylethylenediamine 23, Mgl2, and 2,6-lutidine, the Diels-Alder product 26 was obtained in 64 % yield with 97 % ee (Sch. 9). 

A-Sulfonylaldimines produced by condensation of SES-NFI2 with various aldehydes are converted into enantiomerically enriched aziridines upon reaction with certain sulfur ylides. The same types of aldimines undergo [3 4- 2] cycloaddition reactions with 2,3-butadienoates in the presence of triphenylphosphine to give 2,5-dihydrop3TToles, while that derived from SES-NSO and ethyl glyoxylate reacts efficiently with chiral sulfonimidoyl substituted bis(allyl)titaniumcorr5)lexes to give /3-alkyl-)/,5-unsaturated a-amino acid derivatives. ... 

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