Photosensitized O2 enables intermolecular alkene cyclopropanation by active methylene compounds

• 成果类型: Article
• 署名作者: Poudel, Dhruba P.; Pokhrel, Amrit; Tak, Raj Kumar; Shankar, Majji; Giri, Ramesh
• 署名单位: Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-10835
• DOI: 10.1126/science.adg3209
• 发表日期: 2023-08-04
• 页码: 545-553
• 关键词: light photoredox catalysis; intramolecular cyclopropanation; esters; reactivity; complexes; efficient; alkyl

摘要

Cyclopropanes are key features in many preclinical, clinical, and commercial drugs, as well as natural products. The most prolific technique for their synthesis is the metal-catalyzed reaction of an alkene with a diazoalkane, a highly energetic reagent requiring stringent safety precautions. Discovery of alternative innocuous reagents remains an ongoing challenge. Herein, we report a simple photoredox-catalyzed intermolecular cyclopropanation of unactivated alkenes with active methylene compounds. The reaction proceeds in neutral solvent under air or dioxygen (O-2) with a photoredox catalyst excited by blue light-emitting diode light and an iodine co-catalyst that is either added as molecular iodine or generated in situ from alkyl iodides. Mechanistic investigations indicate that photosensitized O-2 plays a vital role in the generation of carbon-centered radicals for both the addition of active methylene compounds to alkenes and the ring closure.