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

The superbasic mixt. of butyllithium and potassium tert-butoxide 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 derivs. becomes readily accessible, among them 4,4'-di-tert-butylbiphenyldiyl-2,2'-dicarboxylic acid and 4,4'-di-tert-butylbiphenyl-2,2'-diol. The latter compd. can be subjected again to a superbase-promoted double metalation, thus giving rise to 2,2',6,6'-tetrasubstituted biphenyl derivs. [on SciFinder (R)]