Chiral Brønsted Acid as a True Catalyst: Asymmetric Mukaiyama Aldol and Hosomi–Sakurai Allylation Reactions

Highly diastereo- and enantioselective Mukaiyama aldol reaction catalyzed by a new chiral Brønsted acid, N-(perfluorooctanesulfonyl)­thiophosphoramide, is described. The perfluorooctyl substituent on the sulfonyl group of the catalyst plays an essential role in the stereoselection. The catalyst also allows the asymmetric Hosomi–Sakurai allylation, which has been considerably challenging due to the low reactivity of allylsilanes. 29Si and 31P NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Brønsted acid even in the presence of excess silyl nucleophiles, which cannot be found in other related phosphoric acid analogues.