Chiral Bronsted 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 Bronsted acid, N-(perfluorooctanesulfonyl)-thiophosphoramide, is described. The perfluotooctyl 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. (29)S1 and P-31 NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Bronsted acid even in the presence of excess silyl nudeophiles, which cannot be found in other related phosphoric acid analogues.