Regio- and Stereospecific Nucleophilic C3-Azidation of Spiroaziridine Oxindoles: Synthesis of Enantiopure 3-Azido- and 3-Triazole-2-oxindoles

The first regio- and stereospecific nucleophilic azidation at the tertiary C3-(sp³-carbon) center of spiroaziridine oxindoles is developed using inexpensive trimethylsilyl azide (TMS-azide) under catalyst-free and ambient conditions for the exclusive synthesis of 3-azido oxindoles with excellent yield and enantioselectivity (ee up to >99%). The method is robust and scalable. 3-Azido oxindole is employed to synthesize 3-amino- and 3-triazole oxindoles via Staudinger reduction and click chemistry, respectively. Further, it provides an opportunity to merge oxindole units with clinically used drugs like norethindrone and danazol.