The chemistry of pentavalent organobismuth reagents. Part 8. Phenylation and oxidation of alcohols by tetraphenylbismuth esters

Abstract

Tetraphenylbismuth trifluoroacetate under neutral or slightly acidic conditions O-phenylates primary alcohols in reasonable (65–75%) yield, but gives only moderate yields with secondary alcohols and no O-phenylation with tertiary alcohols. An S_N2 type mechanism is proposed with attack of oxygen on aryl carbon. In contrast, the reaction of Bi^V reagents with alcohols under basic conditions gives, exclusively, oxidation, often with benzene as a leaving group. The presence of a Bi^V intermediate with a bismuth–oxygen bond has been proved in several different ways using n.m.r. spectroscopy. Thus the reactions of alcohols with Bi^V reagents parallel the corresponding reactions with phenols.