Useful preparation of 6-phenyl-2,2'-bipyridine ligands bearing Di-n-butylaminophenyl or gallate derivatives substituted in the 3-or 4-positions

A simple protocol for the efficient preparation of substituted 6-phenyl-2,2'-bipyridine derivatives is described. A reverse type of Diels-Alder reaction between a 6-phenyl-2-pyridyl-1,3,4-triazine and 4-N,N-di-n-butylaminophenyl- or gallate-ethynyl derivatives at high temperature provide a mixture of two products easily separable by column chromatography. A variety of ligands suitable for the synthesis of cyclometalated platinum complexes have been produced. Additional substitution of the Pt-Cl by various donor-acceptor ethynyl fragments is feasible by mean of copper(I) catalysis.