Visible-light-driven synthesis of benzoxepine derivatives from aromatic diazo compounds

Abstract

The most well-known reaction between diazo compounds and alkenes is cyclopropanation, which proceeds via a metal carbene or free carbene intermediate. In recent years, significant progress has been made in visible-light photocatalysis of diazo compounds to generate radicals and subsequent functionalization reactions. In this work, the photocatalytic intramolecular radical cyclization of aryl diazo compounds has been developed, resulting in the formation of benzoxepine derivatives with moderate yields. Mechanistic experiments support the formation of a carbon-centered radical from the diazoalkane via a proton-coupled electron transfer (PCET) process. This reaction, which is easy to perform, allowing the rapid conversion of aryl diazo compounds into benzoxepine derivatives under mild conditions.