Pokhriyal Ayushi, Singh Karki Bhupal, Kant Ruchir, Rastogi Namrata
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
J Org Chem. 2021 Mar 19;86(6):4661-4670. doi: 10.1021/acs.joc.1c00082. Epub 2021 Mar 6.
A novel visible light mediated redox-neutral 1,3-dipolar cycloaddition of 2-azirines with 2,4,6-triarylpyrylium tetrafluoroborate salts providing tetrasubstituted pyrroles has been developed. The 2,4,6-triarylpyrylium salt acts as dipolarophile as well as photosensitizer in the reaction, under blue light irradiation. The control experiments indicated single electron oxidation of 2-azirines by photoexcited pyrylium salts, followed by coupling between an azaallenyl radical cation and triarylpyranyl radical as the key mechanistic feature. The mild conditions, wide substrate scope, and complete regioselectivity are the noticeable attributes of the reaction.
已开发出一种新型可见光介导的2-氮杂环丙烷与四氟硼酸2,4,6-三芳基吡喃鎓盐的氧化还原中性1,3-偶极环加成反应，可提供四取代吡咯。在蓝光照射下，2,4,6-三芳基吡喃鎓盐在反应中既作为亲偶极体又作为光敏剂。对照实验表明，光激发的吡喃鎓盐对2-氮杂环丙烷进行单电子氧化，随后氮杂烯丙基自由基阳离子与三芳基吡喃基自由基之间发生偶联，这是关键的机理特征。该反应的温和条件、广泛的底物范围和完全的区域选择性是其显著特点。
