Organic chemistry: Shape control in reactions with light.

Abstract

The report of a light-activated catalyst that dictates the three-dimensional shape — the stereochemistry — of molecules formed in an organic reaction suggests a new strategy for controlling such reactions using visible light. See Letter p.100 The growing demand for optically active compounds in the chemical and pharmaceutical industries is focusing attention on asymmetric photocatalysis as a potentially economical means of synthesis, combining visible light photoredox chemistry with asymmetric catalysis. In this manuscript, the authors show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre serves simultaneously as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the 'green' synthesis of non-racemic chiral molecules.