Cationic Cyclizations of Ketene Dithioacetals: A General Synthesis of Pyrrolizidine, Indolizidine, and Quinolizidine Alkaloid Ring Systems

Article abstract of DOI:10.1021/jo00184a002

Cyclizations of ketene dithioacetals have been applied to the synthesis of pyrrolizidine, indolizidine, and quinolizidine alkaloid ring systems.This new cationic cyclization terminator allows the efficient formation of 5-, 6-, and 7-membered heterocyclic rings, as illustrated by the preparation of 10a-e.Several of these products, available in three steps, have been converted into the known alkaloids (+/-)-supinidine, (+/-)--trachelanthamidine, (+/-)-elaeokanine A, and (+/-)-epi-lupinine.