Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines and followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines and in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine () gave pyrrolizidine having the same stereochemistry as that obtained from the E isomer .