ARYL RADICAL CYCLIZATIONS ONTO ENAMINE DOUBLE-BONDS

Aryl radicals from N-alkyl-N-(2-bromobenzyl)-1-cyclohexenylamine 2 and N-alkyl-N-(2-bromobenzyl)-cyclopentenylamine 11 cyclize readily onto the enamine double bond by 6-endo and 5-exo closure. In the case of 2, 6-endo cyclization is the major pathway; however, the 6-endo to 5-exo ratio is dependent upon the N-alkyl substituent. In both cases, the dominant isomer from 6-endo cyclization is the cis isomer. For 2a in toluene, values of k6-endo and k5-exo at 80-degrees-C were 4.6 X 10(8) s-1 and 1.5 x 10(8) s-1, respectively.