ZnO-nanoparticles as an Efficient Catalyst for the Synthesis of Functionalized Benzenes: Multicomponent Reactions of Sulfonoketenimides.

Abstract

Functionalized benzenes are prepared from the reaction of sulfonoketenimides that is produced from the Copper catalyzed reaction of terminal alkynes and sulfonyl azides with zwitterionic intermediate that is generated from the reaction of dialkyl acetylenedicarboxylates, alkyl bromides and triphenylphosphine in the presence of ZnO-nanoparticles in good yields. All chemicals employed in this work were prepared from Fluka (Buchs, Switzerland) and were used without further purification. Nanoparticles of ZnO were synthesized according to literature report. Melting points were measured on an Electrothermal 9100 apparatus. Elemental analyses for C, H, and N were performed using a Heraeus CHN–O-Rapid analyzer. Mass spectra were recorded on a FINNIGAN-MAT 8430 spectrometer operating at an ionization potential of 70 eV. IR spectra were measured on a Shimadzu IR-460 spectrometer. 1H, and 13C NMR spectra were measured with a BRUKER DRX-500 AVANCE spectrometer at 500.1 and 125.8 MHz, respectively. In these reactions, the first step is optimization of reaction conditions for achieving best conditions. For this reason, solvent, catalyst, and reaction time is changed so that the best result is obtained. For optimization, several catalysts such as CuI, CuBr, CuCl, ZnO-nanoparticles, CM-ZnO, pyridine, piperidine, CuO-NPs, TiO2-NPs and copper powder were checked. Among them CuI and ZnO-NPs give the best results. Also, several solvents such as CH3CN, H2O, solvent-free conditions, toluene and diethyl ether are employed and CH3CN is the best solvent. In summary, sulfonoketenimides react with intermediate that is generated from the reaction of dialkyl acetylenedicarboxylate, alkyl bromides and triphenylphosphine in the presence of ZnO-NPs (10 mol%) to produce benzene derivatives in good yields.