Construction of azaheterocycles via Pd-catalyzed migratory cycloannulation reaction of unactivated alkenes.

Abstract

Azahetereocycles constitute important structural components in many biologically active natural compounds and marketed drugs, and represent the most promising scaffolds in drug discovery. Accordingly, the development of efficient and general synthetic methods for the construction of diverse azaheterocycles is the major goal in synthetic chemistry. Herein, we report the efficient construction of a wide range of azaheterocycles via a Pd-catalyzed migratory cycloannulation strategy with unactivated alkenes. This strategy enables the rapid synthesis of a series of 6-, 7- and 8-membered azaheterocycles in high efficiency, and features a broad substrate scope, excellent functional group tolerance under redox-neutral conditions. The significance of this finding is demonstrated by the efficient synthesis of drug-like molecules with high step-economy. Preliminary mechanistic investigations reveal that this reaction underwent a sequentially migratory insertion to alkenes, metal migration process, and the aza-Michael addition to a quinone methide intermediate.