Visible-Light-Induced Oxazoline Formations from N-Vinyl Amides Catalyzed by an Ion-Pair Charge-Transfer Complex

Abstract

Visible-light photoredox catalysis plays an important role in various reactions which are inaccessible under typical thermal conditions. Distinctly different from common visible-light photoredox catalysis which often involves transition-metal complexes, conjugated organic dyes, or electron donor–acceptor complexes, herein, the use of ion-pair charge-transfer (IPCT) complex-induced visible-light photoredox catalytic reactions are described, wherein the cyclization–methoxylation of N-vinyl amides in methanol was achieved under irradiation with blue LEDs. The reaction employs a heteroarenium iodide as the photocatalyst and can be extended to cyclization–alkoxylation, −acyloxylation, and −hydroxylation. This protocol provides an eco-friendly synthetic route to a wide range of oxazoline derivatives. Mechanistic investigations with UV–visible spectroscopy and control experiments confirm the existence of the IPCT absorption band in the visible region for the heteroarenium iodide, which is responsible for the observed reactivity.