Indium triflate catalyzed microwave-assisted alkenylation of methoxyphenols: synthesis of indenes and chromenes

Abstract

In(OTf)₃ catalyzed microwave-assisted alkenylation of methoxyphenols was investigated. Exclusive formation of either indenes or chromenes was observed depending on the position of the methoxy group on phenol. The structures of 1H-inden-4-ol derivatives (4a–e) and 4H-chromene derivatives (5a–j) were established by NMR (¹H & ¹³C) and high-resolution mass spectra, which were further supported by single crystal X-ray analysis of 4c and 5a.