Visible‐Light Photoredox‐Catalyzed Semipinacol‐Type Rearrangement: Trifluoromethylation/Ring Expansion by a Radical–Polar Mechanism. Issue 39 (1st June 2015) - Sahoo, Basudev
Abstract: A visible‐light‐mediated photoredox‐catalyzed semipinacol‐type rearrangement proceeding via 1, 2 alkyl migration was developed. In this transformation, trifluoromethylation of the CC bond of α‐(1‐hydroxycycloalkyl)‐substituted styrene derivatives is followed by ring expansion of the 1‐hydroxycycloalkyl group to deliver novel cycloalkanones with all‐carbon quaternary centers. The reaction proceeds via a radical–polar mechanism, with trifluoromethylation (radical) and ring expansion (ionic) occurring in the same transformation. Abstract : Circle of light: A visible‐light‐mediated photoredox semipinacol‐type rearrangement proceeding by 1, 2 alkyl migration was developed. The transformation involves a radical–polar mechanism, in which photoinduced trifluoromethylation of a CC bond is followed by ring expansion of a cationic intermediate. This process constitutes the first report of ionic alkyl migration in photoredox catalysis and proceeds under mild conditions with visible light.