DBU-catalyzed [3 + 2] cycloaddition and Michael addition reactions of 3-benzylidene succinimides with 3-ylidene oxindoles and chalcones.

A metal-free DBU catalyzed protocol has been developed for the regioselective [3 + 2] cycloaddition reactions of 3-benzylidene succinimides with 3-ylidene oxindoles to furnish spirooxindole derivatives. The 3-benzylidene succinimides underwent Michael addition with chalcones to provide benzylidene succinimide-tethered propanones. All the reactions proceeded under mild conditions and the products were isolated by simple filtration and washing with ethanol in good yields. The current methodology utilizes simple precursors and provides functionally-rich succinimides with two to five contiguous stereocenters in excellent diastereoselectivity and with complete regioselectivity.