Bis-phosphoric acid derived from BINOL dimer as a chiral brønsted acid catalyst for enantioselective transformations

A chiral bis-phosphoric acid derived from a BINOL (1,1¤-bi-2-naphthol) dimer as a chiral backbone was developed. The catalytic efficiency of this bis-phosphoric acid was compared with that of a reported bis-phosphoric acid having a single BINOL backbone in the Diels-Alder reaction of acrolein with 1,3-dien-1-ylcarbamate. The detailed structural analysis of these bis-phosphoric acid catalysts, coupled with the stereochemical outcome of the Diels-Alder reaction, led to the identification of the specific properties of the bis-phosphoric acid catalysts responsible for the high enantioselectivity.