2-Arylnaphthoxazole-derived palladium(II) complexes as phosphine-free catalysts for Heck reactions

Four air- and moisture-stable new palladium(II) complexes 2a–2c and 4 have been synthesized from easily available 2-arylnaphthoxazole derivatives. The detailed structures of 2c and 4 have been determined by single-crystal X-ray analysis. The Pd–N, Pd–C bonds in palladacycle complexes 2a–2c and the Pd–N, Pd–O bonds in complex 4 form the basis for five- and six-membered chelate rings, respectively. These complexes were applied as efficient phosphine-free catalysts for Heck reactions with aryl bromides and ethyl acrylate. Typically, in the presence of two equivalent n-Bu4NBr, using 0.01% of palladacycle complex 2c as catalyst and two equivalent of K2CO3 as base in DMF at 140 °C provided coupled products in moderate to high yields.

Graphical abstractFour air- and moisture-stable palladium(II) complexes have been synthesized from 2-arylnaphthoxazoles and shown to function as efficient phosphine-free catalysts for the Heck reaction with aryl bromides and ethyl acrylate.Figure optionsDownload full-size imageDownload as PowerPoint slide