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Regio‐ and Diastereoselective Synthesis of α‐Cyanoamines by Anodic Oxidation of 6‐Membered α‐Silylamines
Author(s) -
Le Gall Erwan,
Hurvois JeanPierre,
Sinbandhit Sourisak
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199910)1999:10<2645::aid-ejoc2645>3.0.co;2-4
Subject(s) - chemistry , iminium , cyanation , regioselectivity , chemoselectivity , deprotonation , silylation , cyanide , medicinal chemistry , radical ion , piperidine , redox , amine gas treating , electrochemistry , tertiary amine , dication , organic chemistry , catalysis , ion , electrode
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 cis diastereoisomer 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.