Intramolecular cyclization of phenol derivatives with CC double bond in a side chain

Intramolecular cyclization of phenol derivatives with CC double bond on a side chain was examined using copper and silver catalyst. For example, 2-allylphenol (1a) was converted to 2,3-dihydro-2-methylbenzofuran (2a) in 70% yield using Cu(OTf)2 or in 90% yield using AgClO4. This catalysis was applied to cyclization of 2-allylphenol derivatives, 2-(3-butenyl)phenol, benzoic acids with CC double bond, 2-allyl-N-tosylaniline, and 2-(3-butenyloxy)phenol. Furthermore, allyl phenyl ether was converted to 2a via Claisen rearrangement and cyclization.

Graphical abstractPhenols with olefinic side chain were effectively cyclized to 2,3-dihydrobenzofuran, 3,4-dihydro-2H-1-benzopyrane, 3,4-dihydro-2H-1,5-benzodioxepin by copper or silver catalyst.Figure optionsDownload full-size imageDownload as PowerPoint slide