Synthesis of Benzazepines Bearing Three Contiguous Carbon Stereocenters through Pd(II)-Catalyzed [3 + 2] Cycloaddition of -Aryl Nitrones with Allenoates.

A cascade reaction of Pd(II)/dppben-catalyzed [3 + 2] cycloaddition of -aryl nitrones with allenoates and sequential reduction has been developed for the synthesis of functionalized benzazepines bearing three contiguous carbon stereocenters in moderate to good yields ranging from 15 to 82% and high diastereoselectivity. The obtained benzazepines could be converted into various benzazepine scaffolds, and an estrone-derived benzazepine scaffold was prepared over four steps from estrone. More importantly, chiral benzazepine bearing three contiguous carbon stereocenters could be obtained in 88% ee value with chiral auxiliary.