Asymmetric palladacycle complexes with N,O-bidentate barbiturate ligands: Preparation, characterization and catalytic application in Suzuki-Miyaura reaction

Three N,O-chelate ligands (1a-1c) were synthesized by the reaction of aniline derivatives with 1,3-dimethyl-2,4,6-trioxohexahydropyrimidine-5-carbaldehyde. The corresponding palladacycles complexes (2a-2c) were prepared from treatment of N,O-chelate ligands (1a-1c) with [Pd(mu-OAc)(ppy)](2). The structures of all synthesized compounds were characterized by elemental analyses, ATR-FTIR, H-1- and C-13 NMR spectroscopy. Crystal structures of Pd(II) complexes 2a and 2c were determined by single crystal X-ray diffraction. X-ray diffraction studies revealed that the palladium atom in 2a and 2c has distortion of square-planar geometry. Synthesized complexes were tested as catalyst in Suzuki-Miyaura cross-coupling reaction of various aryl bromide with phenyl boronic acid. All complexes behaved as efficient catalyst to produce the biaryls with both high yields and short time under mild reaction conditions. (C) 2019 Elsevier B.V. All rights reserved.