Green Organocatalytic Synthesis of Dihydrobenzofurans by Oxidation–Cyclization of Allylphenols

Abstract

A green and cheap protocol for the synthesis of dihydrobenzofurans via an organocatalytic oxidation of o-allylphenols is presented. The use of 2,2,2-trifluoroacetophenone and H2O2 as the oxidation system, leads to a highly useful synthetic method, where a variety of substituted o-allylphenols were cyclized in high yields.

Organocatalytic activation of hydrogen peroxide: towards green and sustainable oxidations

“…Kokotos and coworkers, having developed a series of organic transformations using 2,2,2-trifluoroacetophenone (3) as a potent catalyst, expanded its use towards one-pot transformations. A strategically placed functional group next to the formed epoxide was able to perform an intramolecular cyclization reaction, leading to the formation of various substrates, such as dihydrobenzofurans, 31 isoxazolines, 32 lactones, 33 indolines and pyrrolidines ( Scheme 12 ). 34 In these cases, the aqueous buffer solution also provides the appropriate pH for the in situ deprotonation of the OH, N–OH, COOH and NH groups, enhancing their nucleophilicity and facilitating the ring opening of the epoxide ( Scheme 12 ).…”