An unexpected course in the 6-exo radical cyclizations of trichloroacetamides on changing the N-substituent from benzyl to alpha-methylbenzyl

Radical cyclization of N-(alpha -methyl)benzyl substituted trichloroacetami des upon alpha,beta -unsaturated nitriles has been studied. Tributyltin hyd ride treatment of trichloroacetamides 5a and 5b gives morphan derivatives ( 1 and 2). through a 6-exo-trig radical cyclization, and unexpectedly normor phans 6 and 7 as a result of a stereoespecific process in which che stereog enic benzylic carbon undergoes a configurational inversion. (C) 2001 Academ ie des sciences / Editions scientifiques et medicales Elsevier SAS.