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Pure Appl. Chem., 2012, Vol. 84, No. 12, pp. 2609-2617

Published online 2012-06-29

Integrated reactions using addition to conjugated imines and iminium salts

Takafumi Nishi, Isao Mizota and Makoto Shimizu*

Department of Chemistry for Materials, Mie University, Tsu, Mie 514-8507, Japan

Abstract: Recently, nucleophilic addition reactions to imino functions have been utilized in many crucial steps for the synthesis of bioactive and functional materials. This article summarizes the integrated “umpolung” reactions of α-imino esters and the use of iminium salts as reactive electrophiles. Regarding the umpolung reactions, the following five reactions are discussed: (1) N-alkylation/homocoupling; (2) tandem N-ethylation/C-allylation; (3) tandem N-ethylation/C-cyanation; (4) reduction of imines with tris(trimethylsilyl)aluminum; and (5) N-alkylation and Claisen rearrangement. Moreover, the generation and reactions of alkoxycarbonyl iminium species are also discussed. These are prepared easily from trisubstituted amino ketene silyl acetals by oxidation, and the subsequent nucleophilic addition of various nucleophiles readily affords the addition products.