Radical-Induced Metal-Free Alkynylation of Aldehydes by Direct CH Activation

A direct C(sp(2))H alkynylation of aldehyde C(O)H bonds with hypervalent iodine alkynylation reagents provides ynones under metal-free conditions. In this method, 1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one (TIPS-EBX) constitutes an efficient alkynylation reagent for the introduction of the triple bond. The substrate scope is extended to a variety of (hetero)aromatic, aliphatic, and ,-unsaturated aldehydes.