Chiral Phosphoric Acid-Catalyzed Enantioselective Formal [3+2] Cycloaddition of Azomethine Imines with Enecarbamates
The first catalytic asymmetric inverse electron demand 1,3-dipolar cycloaddition of azomethine imines with enecarbamates has been developed. Isoquinolinefused pyrazolidines containing two or three contiguous stereogenic centers were obtained in high yields with excellent regio-, diastereo-, and enantioselectivities. The pyrazolidine ring can be opened to install an aminal, a amino nitrile, or homoallylamine function with an excellent control of the newly generated stereogenic center. Access to aminobenzo[a]quinolizidine is also documented.