The classic Norrish-Yang cyclization of ketones and their alkene counterparts is a well-known photochemical rearrangement strategy utilized for building cyclobutanes through hydrogen atom transfer. Herein, a noncanonical Norrish-Yang-type rearrangement involving the migration of functional groups, such as cyano and aryl, is established through energy transfer catalysis, facilitating facile assembly of three-membered cyclopropanes. With a focus on reactions translocating a cyano group, this protocol showcases a broad substrate scope (58 entries), operates under mild reaction conditions, and requires an extremely low catalyst loading (100 ppb, 12 h, 97% yield). Impressively, a total turnover number (TTN) of 1.15 × 10⁷ was recorded. Mechanistic experiments uncovered a unique fluorescence enhancement phenomenon of photocatalysts, characterized by a linear Stern-Volmer plot with an unusual negative slope. The present Norrish-Yang-type cyclization significantly expands the synthetic repertoire of photochemical rearrangement for preparing distinct ring frameworks.

中文翻译：

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Norrish-Yang型环丙烷化，通过光敏剂在ppb负载量下进行官能团迁移


酮及其烯烃对应物的经典 Norrish-Yang 环化是一种众所周知的光化学重排策略，用于通过氢原子转移构建环丁烷。在此，通过能量转移催化建立了涉及氰基和芳基等官能团迁移的非经典 Norrish-Yang 型重排，促进了三元环丙烷的轻松组装。该方案侧重于反应转位氰基，展示了广泛的底物范围（58 个条目），在温和的反应条件下运行，并且需要极低的催化剂负载（100 ppb，12 小时，97% 产率）。令人印象深刻的是，总成交率 （TTN） 为 1.15 × 10⁷。机理实验揭示了光催化剂的一种独特的荧光增强现象，其特征是线性 Stern-Volmer 图具有不寻常的负斜率。目前的 Norrish-Yang 型环化显着扩展了光化学重排的合成库，用于制备不同的环框架。