Sustainable Photocatalytic Synthesis of Glitazones via Riboflavin Tetraacetate

A more sustainable and versatile method to access antidiabetic glitazones is demanded. Herein, we report the unprecedented photocatalytic coupling of N-protected methylene thiazolidinediones with radical precursors (organoborates or carboxylic acids) under riboflavin tetraacetate catalysis. The methodology accepts various functional groups and affords (Het)Ar-(CH₂)_n-thiazolidinediones by transition-metal-free organic photoredox catalysis under mild conditions. The applicability of the developed protocol is showcased by the three-step preparation of the antidiabetic pioglitazone drug.