Control of Reaction Enantioselectivity with a Molecular Motor Switch

Significance

Wang and Feringa describe the use of molecular motor 1 as a chiral switchable organocatalyst. Molecular motor 1 decorated with Brønsted acidic thiourea and Brønsted basic DMAP groups can be driven through an unidirectional rotatory cycle with a series of two photo­isomerizations and two thermal isomerizations. The rotation of the molecular motor provides the means to control the relative orientations of the two catalytic moieties. It was demonstrated that different preformed isomers of the molecular motor enable the switching of the enantioselectivity of the addition of o-methoxythiophenol to cyclohexanone. The (R)- and (S)-enriched or racemic products can be obtained depending on the rotational state of the catalyst.