Synthesis, characterization, and microwave-assisted catalytic activity in Heck, Suzuki, Sonogashira, and Buchwald-Hartwig cross-coupling reactions of novel benzimidazole salts bearing N-phthalimidoethyl and benzyl moieties

Abstract

Five novel benzimidazole salts (1-5) having N-phthalimidoethyl and 4-substituted benzyl were synthesized and identified by H-1 NMR, C-13 NMR, and IR spectroscopic methods and microanalysis. A mixture of the benzimidazole salts (1-5), Pd(OAc)(2), and K2CO3 in DMF-H2O catalyzed, in high yield, the Suzuki-Miyaura and the Heck-Mizoroki cross-coupling reactions assisted by microwave irradiation in 5 min. The novel benzimidazole salts (1-5), Pd(OAC)(2), CS2CO3, PEG, and Cu nanoparticles catalyzed, in high yield, the Sonogashira coupling reaction promoted by microwave irradiation in 10 min. The same benzimidazole salts (1-5), Pd(OAc)(2), CS2CO3, and TBAB catalyzed, in moderate or low yield, the Buchwald-Hartwig reaction assisted by microwave irradiation in 60 min. The efficiency of the catalyst system in these four reactions was discussed as well as the electron-releasing and withdrawing substituent effects on the benzimidazole ligands.