Trifluoromethyl-substituted tetrakis(triphenylphosphine)palladium catalysts, process for their preparation and their use in Suzuki coupling.

Abstract

Pd{P[3,5-(CF3)2C6H3]3}4 (I) and Pd{P[4-(CF3)C6H4]3}4 were prepd. by complexation of a Pd(II) salt with indicated ligands (L) followed by redn. of thus-formed PdIIL4 complexes with hydrazine hydrate, and evaluated as catalysts for Suzuki coupling. Thus, e.g., reaction of 2-(4-ethoxy-3-methylphenyl)-1,3,2-dioxaborolane with 2-bromopyridine (substrate) in 10:1 vol:vol MeOH:H2O at 110° afforded 89% 2-(4-ethoxy-3-methylphenyl)pyridine with 100% conversion using 1 mol % I (relative to substrate) in 1 h; 39% yield with 50% conversion was obsd. with use of only 0.005 mol % I in 1 h, and in no case was Pd black obsd. When Pd(PPh3)4 was used in place of I the reaction mixt. darkened within minutes and even after removal of Pd black the product remained orange-yellow (vs. snow-white using I). [on SciFinder(R)]