A highly diastereoselective [5+1] annulation to 2,2,3-trisubstituted tetrahydroquinoxalines via intramolecular Mannich-type trapping of ammonium ylides.

A novel tandem intermolecular ammonium ylide formation/intramolecular Mannich-type [5+1] cyclization reaction of aryl diazoacetates and ortho-aminophenyl imine derivatives was developed. The reaction provides an efficient methodology for direct synthesis of diverse trisubstituted tetrahydroquinoxalines bearing a quaternary stereogenic carbon center in moderate to good yields with excellent diastereoselectivity. This process features high efficiency, mild reaction conditions, and high stereoselectivity.