One-Pot Synthesis of Enantiopure Spiro[3,4-dihydrobenzo[b][1,4]oxazine-2,3'-oxindole] via Regio- and Stereoselective Tandem Ring Opening/Cyclization of Spiroaziridine Oxindoles with Bromophenols.

A highly efficient regio- and stereoselective spiroaziridine ring opening with 2-bromophenols and a subsequent tandem cyclization reaction was developed for the one-pot synthesis of enantiopure 3,4-dihydrospiro[benzo[b][1,4]oxazine-2,3'-oxindole] with excellent enantiopurity (ee up to >99%). It is further extended to asymmetric synthesis of NH-free 3,4-dihydrospiro[benzo[b][1,4]oxazine-2,3'-xindole] retaining the optical activity.

Organocatalytic Domino Reaction of Spiroaziridine Oxindoles and Malononitrile for the Enantiopure Synthesis of Spiro[dihydropyrrole-3,3'-oxindoles].

The first organocatalytic regio- and stereoselective domino reactions of spiroaziridine oxindoles and malononitrile have been developed using DBU as a catalyst without any metal/Lewis acid activation for the enantiopure synthesis of spiro[dihydropyrrole-3,3'-oxindoles] (ee up to >99%). The protocol is also equally effective for the phenyl aziridine with excellent regio- and stereoselectivity.