Asymmetric additions to dienes catalysed by a dithiophosphoric acid

Asymmetric catalysis branches out Previous work on nucleophilic additions catalysed by chiral Brønsted acids has been restricted to polarized heteroatom-containing functionalities such as imines, aziridines and carbonyls. This limitation has yet to be overcome despite the fact that acid-catalysed 'Markovnikov' additions to olefins have been known for more than a century. Here the authors show that chiral dithiophosphoric acids can catalyse the intramolecular hydroamination and hydroarylation of dienes and allenes to generate heterocyclic products in exceptional yield and enantiomeric excess. They present a mechanistic hypothesis that involves the addition of the acid catalyst to the diene, followed by SN2′ displacement of the resulting dithiophosphate intermediate. The proposed mechanism is supported by mass spectroscopy and deuterium labelling studies.