Visible-Light-Triggered Oxidative C-H Aryloxylation of Phenolic Amidines; Photocatalytic Preparation of 2-Aminobenzoxazoles

Visible light efficiently mediates an intramolecular cyclization reaction of o-hydroxy-N-aryl-N,N-dialkylformamidines (phenolic amidines) leading to 2-aminobenzoxazole derivatives in the presence of only 1 mol% tris(2,2-bipyridine)ruthenium(II) as a photoredox catalyst along with air as terminal oxidant. The protocol involves oxidative functionalization of an amidinic C-H bond to a C-O bond and affords excellent yields of products in a simple one-pot operation under mild conditions. The method represents the first example of an oxidative C-H aryloxylation reaction implementing visible-light-driven aerobic photoredox catalysis.