Photocatalyst- and transition-metal-free syntheses of furan-fused dihydroazepines by visible light

Abstract

The visible-light-induced atom-economical synthesis of furan-fused dihydroazepine derivatives under transition-metal and photocatalyst-free conditions is presented. This efficient new method exhibits a broad scope and is environmentally benign and mild with metal-/photocatalyst and external additive-free conditions and moderate to good yields. Several late-stage modifications of the obtained compounds have been accomplished, including the successful synthesis of tetrahydro-6H-benzo[4′,5′]azepino[3′,2′:4,5]furo[3, 2-c]quinolin-6-ones. Additionally, the reaction mechanism has been studied by several control experiments, including the successful isolation of the reaction intermediate. These results reveal that the transition-metal and photocatalyst-free transformation may proceed via non-radical pathways. The gram-scale reaction renders the approach practical and attractive. Also, the green chemistry metrics evaluation signifies that the process is green and cost-effective.