Organocatalytic (3+3)-cycloaddition of ortho -substituted phenyl nitrones with aryl cyclopropane carbaldehydes: a facile access to enantioenriched 1,2-oxazinanes.

The first asymmetric (3+3)-cycloaddition of ortho -substituted phenyl nitrones with aryl cyclopropane carbaldehydes has been demonstrated by secondary amine catalysts. While the other ortho -substituents gave 1,2-oxazinanes, ortho -hydroxy ones provided a novel class of tetrahydrochromeno-1,2-oxazine cores via rare 1,3-aryl migration, followed by cyclization. An unusual type of asymmetric approach was also recognized.