In situ intramolecular catalytic 1,2-addition of allenoates to cyclic ketones towards polycyclic allenoates

Abstract

Sequential deprotonation, isomerization of 3-alkynoates and subsequent 1,2-addition led to bicyclic allenoate in the presence of a catalytic amount of Cs₂CO₃. Cyclization proceeds in a totally stereoselective manner in the case of the two-carbon linker chain. A one-pot reaction starting from alkynyl ketones afforded tricyclic fused ring systems with good yields.