Rhodium-Catalyzed Regiodivergent [3 + 2] and [5 + 2] Cycloadditions of Quinolinium Ylides with Alkynes

Org Lett. 2019 Jul 5;21(13):5167-5171. doi: 10.1021/acs.orglett.9b01765. Epub 2019 Jun 18.

Abstract

Rhodium-catalyzed regiodivergent [3 + 2] and [5 + 2] cycloadditions of quinolinium ylides with alkynes are reported, providing highly functionalized five-membered indolizine derivatives and seven-membered 1,4-oxazepine compounds, respectively, in moderate to excellent yields under mild reaction conditions. Importantly, quinolinium ylides are derived from donor-acceptor diazo compounds, and different types of donor-acceptor diazo compounds exhibit distinct selectivity and reactivity for the reactions. The [3 + 2] cycloadditions involve an unusual 1,3-ester migration process.