The Synthesis Of Palladium Complexes Of Benzannulated N-heterocyclic Carbenes And Their Applications To N-arylation Reaction

In this thesis, three new palladium (Ⅱ) complexes of chelating benzannulated N-heterocyclic carbene were synthesized. All the new compounds were fully characterized. The catalytic activity of the palladium (Ⅱ) complexes of chelating benzannulated N-heterocyclic carbene in the N-arylation reaction of imidazoles with aryl and heteroaryl halides was studied. Moreover, three new benzimidazolones were synthesized and characterized. The main results are as follows:1. The benzimidazolium salt la was prepared from commercially available 1,2-benzenediamine,formic acid and benzyl chloride by closing ring reaction and nucleophilic substitution reaction. Then three new palladium (Ⅱ) complexes of benzannulated N-heterocyclic carbene 2a,3a and 4a were successfully synthesized by elimination proton reaction of la with Pd(OAc)2 or Pd(CH3CN)2Cl2. All the new compounds were characterized by IR,1H NMR,13C NMR, ESI-MS spectra and Elemental analysis. The molecular structure of 3a was further confirmed by single-crystal X-ray analysis. 2. All the palladium complexes of benzannulated N-heterocyclic carbene have been successfully employed in N-arylation reaction of imidazoles with aryl and heteroaryl halides. The optimized reaction conditions was t-BuOK as the base in DMSO at 110℃for 24 h under N2 atmosphere with the mole of ratio of benzimidazole, aryl halides and base is 1:1.2:1.4. Compound 3a was found to be the most active. By using 2 mol% of 3a, the coupled products of benzimidazole with aryl halides could be obtained as high as 98%.3. The compounds 1b-d were prepared from commercially available benzimidazole by nucleophilic substitution reaction with aryl halides. Then lb-d gave to benzimidazolones 5b-d by oxidized reaction in DMF. The new compounds 5b-d were characterized by IR, H NMR and 13C NMR. The molecular structures of 1c and 5c were further confirmed by single-crystal X-ray analysis. The new compounds 5b-d have potential application in biomedicine and pharmacology.