Radical arylation of phenols, phenyl ethers, and furans

Abstract

Radical arylations of parasubstituted phenols and phenyl ethers proceeded with good regioselectivity at the ortho position with respect to the hydroxy or alkoxy group. The reactions were conducted with arenediazonium salts as the aryl radical source, titaniumACHTUNGTRENUNG(III) chloride as the reductant, and diluted hydrochloric acid as the solvent. Substituted biaryls were obtained from hydroxy- and alkoxy-substituted benzylamines, phenethylamines, and aromatic amino acids. The methodology described offers a fast, efficient, and cost-effective new access todiversely functionalized biphenyl alcohols and ethers. Free phenolic hydroxyl groups, aromatic and aliphatic amines, as well as amino acid substructures, are well tolerated. Two examples for the applicability of the methodology are the partial synthesis of a b-secretase inhibitor and the synthesis of a calciumchannel modulator© 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.