Convergent Assembly of 1,4-Benzothiazide Spiroindolinones via [4 + 2] Spiroannulation Under Open-Air Conditions

This report discloses a transition-metal-free [4 + 2] spirocyclization of isatin-derived β-silylcarbinols and 2-aminobenzenethiols, providing a facile approach to 1,4-benzothiazide spiroindolinones in decent yields. Control experiments indicate that 3-methylene oxindoles and disulfides are key intermediates in this tandem reaction. Moreover, the resulting products can be facilely converted into pharmaceutically significant sulfone and sulfoxide scaffolds, which further demonstrates the potential utility of this protocol.