ChemInform Abstract: Regio- and Diastereoselective Synthesis of α-Cyanoamines by Anodic Oxidation of 6-Membered α-Silylamines.

Abstract

The electrochemical cyanation of N-benzyl-substituted cyclic six-membered α-silylamines including tetrahydroquinoline and piperidine derivatives was studied. The results of these investigations demonstrate that α-silylamines are valuable precursors for the preparation of the corresponding α-cyanoamines. The TMS group α to the N atom not only governs the chemoselectivity of the iminium formation through a preferential desilylation reaction under the experimental conditions (i.e., amine cation radical desilylation versus deprotonation), it also lowers the oxidation potential of tertiary amines compared to their non-TMS counterparts. Both the stereoselectivity and regioselectivity of the cyanide addition were investigated with 3-methylpiperidine as the model compound. The formation of a single cisdiastereoisomer in which the 2-cyano group is axial and the 5-methyl group is equatorial, indicates that the addition of the cyanide anion onto the iminium species is under stereoelectronic control. In addition, the redox reaction involving the intermediate nitrogen-centered cation radical and the cyanide anions played no role, because the α-silyl radical has such a short lifetime.