Tandem cyclization of N-allylaminyl radicals: Stereoselective synthesis of1,2,5-trisubstituted pyrrolizidines

Radical reaction of N-allylalk-4-enylaminyl radicals, generated from the co rresponding N-chloroamines by treatment with Bu3SnH-AIBN in refluxing tolue ne, was carried out. Tandem cyclization of the resulting neutral aminyl rad icals readily took place stereoselectively to give 1,2,5-trisubstituted pyr rolizidines and a pyrroloindole derivative as a sole product in good yields . The cyclization products contained only two stereoisomers in each reactio n, indicating that both of the consecutive cyclizations proceeded in a ster eoselective manner. (C) 1999 Elsevier Science Ltd. All rights reserved.