Umpolung Reaction of Imine Analogues and Their Development into Biologically Active Compounds

Nucleophilic additions on imines occur mostly on imino carbons due to their polarization, whereas adducts on imino nitrogens are difficult. However, by adjusting the reaction conditions such as nucleophiles and reaction solvents, the selective Naddition reaction can proceed on the nitrogen atom. This reaction is known as an umpolung reaction, and is an attractive one that allows making nitrogencarbon bonds at will. In this review, based on the umpolung reaction to alpha imino esters, various types of umpolungs for their analogues and the development into biologically active compounds are provided. The review is divided into five parts, namely 1)alpha imino allylesters, 2)alpha imino thioesters, 3)Nsilyl alpha imino esters, 4)alpha hydrazonoesters and 5)gamma hydrazono beta ketoesters;here, the mechanism of the umpolung and their intermediates are discussed.