Molecular Design of a Chiral Bronsted 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 Bronsted acid containing two different acidic sites, chiral carboxylic acid monophosphoric acid la, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels Alder reactions of azopyridine-carboxylate with amidodienes. The multipoint hydrogen bonding interactions among the carboxylic acid, mono phosphoric acid, azopyridinecarboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydropyridazines with excellent stereo control in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels Alder reactions by chiral Bronsted acid catalysis.