Asymmetric Brønsted Acid Catalyzed Cycloadditions of ortho-Quinone Methides and Related Compounds

Abstract This review summarizes recent developments in the area of Brønsted acid catalyzed, enantioselective cycloadditions of ortho-quinone methides, ortho-quinone methide imines as well as heterocyclic indole- and pyrrole-based methides. In a straightforward and single-step transformation complex polycyclic N- and O-heterocyclic scaffolds are accessible, with typically good yields and excellent stereocontrol, from simple benzyl and heterobenzyl alcohols upon acid-catalyzed dehydration. The transient precursors are hydrogen-bonded to a chiral Brønsted acid which controls the enantioselectivity of the process. 1 Introduction 2 Cycloadditions of ortho-Quinone Methides 2.1 Brønsted Acid Catalyzed Processes 2.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes 3 Cycloadditions of ortho-Quinone Methide Imines 4 Cycloadditions of Indolyl-3-methides 5 Cycloadditions of Indolyl-2-methides 5.1 Brønsted Acid Catalyzed Processes 5.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes 6 Cycloadditions of Pyrrolyl-2-methides 7 Cycloadditions of Pyrrolyl-3-methides 8 Conclusions