Photocatalytic Asymmetric Acyl Radical Truce-Smiles Rearrangement for the Synthesis of Enantioenriched α-Aryl Amides

Abstract

The radical Truce-Smiles rearrangement is a straightforward strategy for incorporating aryl groups into organic molecules for which asymmetric processes remains rare. By employing a readily available and non-expensive chiral auxiliary, we developed a highly efficient asymmetric photocatalytic acyl and alkyl radical Truce-Smiles rearrangement of α-substituted acrylamides using tetrabutylammonium decatungstate (TBADT) as a hydrogen atom-transfer photocatalyst, along with aldehydes or C-H containing precursors. The rearranged products exhibited excellent diastereoselectivities (7 : 1 to >98 : 2 d.r.) and chiral auxiliary was easily removed. Mechanistic studies allowed understanding the transformation in which density functional theory (DFT) calculations provided insights into the stereochemistry-determining step.

Keywords: Chiral auxiliaries; Truce–Smiles rearrangement; aryl migration; asymmetric photocatalysis; hydrogen atom transfer (HAT).