Trimethyl Borate Induced Thermal Cycloaromatization of 1‐Aryl‐1‐(prop‐ 2‐ynyl)‐3,3‐bis(alkylthio)‐2‐propen‐1‐ols Through Acetylenic Oxy‐Cope Rearrangement.

The carbinol acetals 2a-h obtained by 1,2-addition of propargylmagnesium bromide to acyclic α-oxoketene dithioacetals 1a-h undergo cycloaromatization in the presence of trimethyl borate/methanol to give 2,5-bis(alkylthio)biphenyls 4a-henic oxy-Cope rearrangement and an unprecedented 1,4-alkylthio shift in the resulting allenic intermediate.