Trace water in a BF 3 ·OEt 2 system: a facile access to sulfinyl alkenylsulfones from alkynes and sodium sulfinates.

A highly efficient and operationally simple method for the synthesis of β-sulfinyl alkenylsulfones through a BF ₃ ·OEt ₂ -promoted reaction of alkynes and sodium sulfinates is developed, successfully avoiding the complicated anhydrous treatment before the reaction and greatly simplifying the reaction conditions. As a facile and selective route to the targets, it features good functional group compatibility, mild conditions, easily available starting materials, and excellent yields. Notably, the trace water in solvent plays a key role in promoting the reaction, which provides a more practical pathway for the utilization of the BF ₃ ·OEt ₂ catalytic system.