Highly stereoselective construction of novel dispirooxindole-imidazolidines via self-1,3-dipolar cyclization of ketimines.

An acid-promoted self-1,3-dipolar cycloaddition of ketimines derived from isatins and benzylamines was successfully developed to assemble unprecedented dispirooxindole-imidazolidine ring systems. Generally, excellent diastereoselectivities (only a single stereoisomer formed) and good yields (up to 94%) were obtained. Consequently, this self-1,3-dipolar cycloaddition protocol offers facile access to a novel dispiroheterocyclic skeleton.