The superbase-mediated pairwise substitution of the 2,2′- and 6,6′-positions in a biphenyl derivative

The superbasic mixture of butyllithium and potassium tertbutoxide is powerful enough to enable the double proton abstraction from one ortho and one ortho' position of 4,4'di-tert-butylbiphenyl. In this way, a series of functionalized derivatives becomes readily accessible, among them 4,4'-ditert-butylbiphenyldiyl-2,2'-dicarboxylic acid (2a) and 4,4'-di- tert-butylbiphenyl-2,2'-diol (2d). The latter compound can be subjected again to a superbase-promoted double metalation, thus giving rise to 2,2',6,6'-tetrasubstituted biphenyl derivatives. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.