Syntheses of Benzofuranoquinolines and Analogues via Photoinduced Acceptorless Dehydrogenative Annulation of o-Phenylfuranylpyridines

A strategy for the syntheses of benzofuranoquinolines and its analogues via the irradiation of o-phenylfuranyl/thienylpyridines/pyrimidines in DCM with UV light at rt under an argon atmosphere is described. The mechanism of this reaction through the process of 6 pi-electrocyclization, [1,5]-hydrogen shift, and 1,3-eneamine tautomerism leading to H-2 evolution was elucidated. Notably, the syntheses of cis-8b-methyl-8b,13a-dihydrobenzo [f]-benzofuro [3,2-h] quinolone via the photoinduced rearrangement of 2-(3-methylbenzofuran-2-yl)-3-phenylpyridine relevant to the mechanism of this reaction highlights the importance of the developed methodology.