1,2-Dicarbofunctionalization of Trifluoromethyl Alkenes with Pyridinium Salts via a Cycloaddition/Visible-Light-Enabled Fragmentation Cascade

Org Lett. 2022 Jan 21;24(2):702-707. doi: 10.1021/acs.orglett.1c04148. Epub 2022 Jan 7.

Abstract

Although trifluoromethyl alkenes have great synthetic potential, their 1,2-difunctionalization has been a challenge. In this Letter, we disclose the first 1,2-dicarbofunctionalization of trifluoromethyl alkenes with pyridinium salts via a cascade process involving a base-promoted [3 + 2] cycloaddition followed by a visible-light-mediated Norrish-type-II fragmentation. This protocol allows for the formation of pyridines bearing a trifluoromethyl-substituted quaternary center in moderate to excellent yields under mild conditions.