2-Aminocyclobutanols are important motifs found in natural product synthesis and pharmaceuticals. Although their synthesis has been reported by modification of cyclobutanes, sustainable methods for polysubstituted 2-aminocyclobutanols remain underdeveloped due to challenges with reactivity and selectivity. In this work, we introduce a visible-light-mediated intermolecular 2 + 2 photocycloaddition for producing polysubstituted 2-aminocyclobutanols. By leveraging triplet energy transfer, oxazolones undergo 2 + 2 cycloaddition with various alkenes, both activated and unactivated. This approach is notable for its simplicity, mild conditions, broad substrate scope, and high regio- and diastereoselectivity, enabling complex molecule synthesis from readily available materials. Additionally, we also demonstrate a highly unusual cycloaddition with vinylcyclopropanes to construct 6,5-fused scaffolds. Finally, mechanistic studies are included, revealing that cycloaddition is achieved through the radical addition of excited state oxazolones to alkenes, followed by radical-radical recombination.
Wang et al. (Mon,) studied this question.