Purple-light-induced synthesis of spiro-oxindole oximes from BCBs and TBN via strain release

Herein, we report a photocatalyst-free, visible-light-driven synthesis of spiro-oxindole oximes from bicyclo[1.1.0]butane (BCBs)-containing o-iodoanilides and tert-butyl nitrite (TBN). TBN serves a dual function in this transformation, acting as both a hydrogen atom transfer (HAT) reagent and the oxime group source. Its homolytic cleavage under visible light irradiation generates key radical species, enabling the subsequent steps. This strategy allows for the efficient and modular incorporation of diverse heterocycles onto the spiro-oxindole oxime scaffold under mild and operationally simple conditions. The successful downstream derivatizations further highlight the synthetic utility of this methodology.