Gold(I)-Catalyzed Allylation and Tandem Allylation–Cycloisomerization of Stannylated Propargyl Acetates with Allylsilanes

Abstract

Bicyclo[3.1.0]hex-2-enes, synthesized by the cycloisomerization of 1,5-enynes, serve as key scaffolds in various natural products. Gold(I)-catalyzed cycloisomerization of 1,5-enynes is an efficient route to bicyclo[3.1.0]hex-2-enes. However, gold(I)-catalyzed 1,5-enyne synthesis, particularly with a terminal alkyne, has not yet been fully explored. This study presents a mild and general method for the gold(I)-catalyzed allylation and tandem allylation–cycloisomerization of stannylated propargyl acetates with allylsilanes, yielding 1,5-enynes with terminal alkyne moiety and bicyclo[3.1.0]hex-2-enes. The catalytic system ((4-MeOC6H4)3PAuCl/AgSbF6) enabled the efficient synthesis of 1,5-enynes with good to high yields and regioselectivities. In addition, gold(I)-catalyzed tandem allylation–cycloisomerization using (JohnPhos)Au(MeCN)SbF6 afforded bicyclo[3.1.0]hex-2-enes with high regiocontrol. Stannylated propargyl acetates proved crucial in enhancing selectivity for both product classes.