Cascade cyclization versus chemoselective reduction: a solvent-controlled product divergence

A simple and efficient strategy for the assembly of polysubstituted thiophenes and the chemoselective reduction of α,β-unsaturated ketones via the reaction of enones with elemental sulfur and by a simple switching of the reaction solvent is described. Mechanistic studies revealed that both the reactions proceeded via radical pathways, and two hydrogen atoms came from H2O in the reduction course.