[3+2] Cycloaddition is a step- and atom-economic method for the synthesis of five-membered rings. Despite the great success of 1,3-dipolar cycloadditions, the radical [3+2] annulation of alkynes remains a formidable challenge. Herein, a photoinduced decatungstate-catalyzed [3+2] cycloaddition of various internal alkynes using abundant aliphatic aldehydes as a three-carbon synthon is developed, producing elaborate cyclopentanones in 100% atom economy with excellent site-, regio-, and diastereoselectivity under mild conditions. The catalytic cycle consists of hydrogen atom abstraction from aldehydes, radical addition, 1,5-hydrogen atom transfer, anti-Baldwin 5-endo-trig cyclization, and back hydrogen abstraction. The power of this method is showcased by the late-stage elaboration of medicinally relevant molecules and total or formal synthesis of (±)-β-cuparenone, (±)-laurokamurene B, and (±)-cuparene.

[3+2] 环加成是一种合成五元环的步骤和原子经济方法。尽管 1,3-偶极环加成反应取得了巨大成功，但炔烃的自由基 [3+2] 环化反应仍然是一项艰巨的挑战。在此，开发了一种使用丰富的脂肪醛作为三碳合成子的光诱导十钨酸盐催化的各种内部炔烃的 [3+2] 环加成反应，在温和条件下以 100% 的原子经济性生产出具有优异的位点选择性、区域选择性和非对映选择性的精细环戊酮。条件。催化循环包括从醛中提取氢原子、自由基加成、1,5-氢原子转移、抗鲍德温 5-endo-trig 环化和反氢提取。