New strategies for the efficient synthesis of medium-sized bicyclic gamma-alkylidenebutenolides based on regioselective cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride

Medium-sized bicyclic gamma -alkylidenebutenolides were efficiently prepare d by Me3SiOTf-catalyzed cyclization of cyclic bis(silyl enol ethers) with o xalyl chloride. In addition, a new strategy for the synthesis of medium-siz ed bicyclic hybrids of butenolides and medium-sized cyclic ethers - based o n sequential [3+2] cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes , Mitsunobu reaction, and ring-closing metathesis - is reported.