CYCLIZATION OF AMINYL RADICALS GENERATED BY ANODIC OXIDATION OF LITHIUM ALKENYLAMIDES. STEREO- AND REGIOSELECTIVE SYNTHESIS OF cis-1-ALKYL-2,5-DISUBSTITUTED PYRROLIDINES

Article abstract of DOI:10.1016/S0040-4020(01)89956-7

Neutral aminyl radicals (3) generated by anodic oxidation of lithium alkenylamides (2) were found to undergo a stereo- and regioselective cyclization to give cis-1-alkyl-2,5-disubstituted pyrrolidines (5c-5h) in moderate yields.The cis stereochemistry of 5c-5h was confirmed by comparison with the corresponding trans-1-alkyl-2,5-disubstituted pyrrolidines which were prepared by aminomercuration of 1c-1h.The structure of trans-1,2-dimethyl-5-phenylpyrrolidine (17) was established by an X-ray crystallographic analysis of its ammonium bromide 21.Various aminyl radicals examined in this study were found to combine exclusively with the internal carbon of their double bond to give a five- (5a-5h) or six-membered ring (13).No product arising from the cyclization is obtained from N-methyl-1-phenylbut-3-enylamine (14).