Molecular Design of a Chiral Brønsted Acid with Two Different Acidic Sites: Regio‑, Diastereo‑, and Enantioselective Hetero-Diels–Alder Reaction of Azopyridine­carboxylate with Amidodienes Catalyzed by Chiral Carboxylic Acid–Monophosphoric Acid

A chiral Brønsted acid containing two different acidic sites, chiral carboxylic acid–monophosphoric acid <b>1a</b>, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels–Alder reactions of azopyridine­carboxylate with amidodienes. The multipoint hydrogen-bonding interactions among the carboxylic acid, monophosphoric acid, azopyridine­carboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydro­pyridazines with excellent stereocontrol in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels–Alder reactions by chiral Brønsted acid catalysis