Alkylations and Additions of Other C-Nucleophiles to Imines

A novel migration-addition sequence has been found for enantioenriched N-t-butylsulfinyl iminoacetate (31) with functionalized benzylzinc bromide reagents, producing t-leucine derivatives (32) in up to 96% de Desulfurization and A-protection 0 to give (33) can then be carried out in 98% ee. (fA 

Imines (34) have been C-alkylated to give amines (35), in an unusual alkyl transfer arising from C-C cleavage. Hantzsch ester analogues such as (36) can act as hydride-transfer agents, but they have now been used to transfer alkyl groups, using Brpnsted or Lewis acid catalysts. Benzyl-substituted dihydropyridines (i.e., 36, with R = Bn) are particularly efficient. Evidence for a concerted transfer process is discussed. 

The alkylation of ambident enolates of a methyl glycinate Schiff base has been studied computationally/ Although the E- and Z-enolates have similar energy and geometry, and similar transition states with ethyl chloride, the -enolate is substantially more stabilized by lithium cation. 

Enantioselective arylation of ketimines has been carried out using rhodium catalysis with chiral sulfur-olefin ligands arylboronic acids are added in up to 99/99% yield/cc. 0 

3-Aryl-3-hydroxyisoindolin-l-ones (37) can be further arylated at the 3-position with an arylboroxine and rhodium(I) catalysis reaction proceeds via dehydration to give a cyclic A-carbonyl ketimine in situ, followed by addition. (S) 

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Enantioselective Alkylations and Additions of Other C-nucleophiles to Imines... 

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