Coumarin or benzoxazinone bearing benzimidazolium and bis(benzimidazolium) salts; involvement in transfer hydrogenation of acetophenone derivatives and hCA inhibition

Abstract

Four new salts of benzimidazolium and bis(benzimidazolium) which include coumarin or benzoxazinone moieties were synthesized and the structures of the newly synthesized compounds were elucidated on the basis of spectral analyses such as 1H-NMR, 13C-NMR, HSQC, IR, LC-MS and elemental analysis. Benzimidazolium salts were used intensively as N-heterocyclic carbene (NHC) precursors in the various catalytic reactions such as transfer hydrogenation (TH), C-H bond activation, Heck, Suzuki reaction etc. With the prospect of potential NHC precursor properties of the synthesized compounds, they were employed in the (TH) reaction of p-substitute acetophenones (acetophenone, p-methyl acetophenone, p-chloro acetophenone) and good yields were observed. Coumarin compounds are known as inhibitor of carbonic anhydrase and inhibition effects of the synthesized compounds on human carbonic anhydrases (hCA) were investigated as in vitro. The in vitro results demonstrated that all compounds inhibited hCA I and hCA II activity. Among the synthesized compounds 1,4-bis(1-((6,8-dimethyl-2H-chromen-2-one-4-yl)methyl)benzimidazolium-3-yl)butane dichloride was found to be the most active IC50= 5.55 mM and 6.06 mM for hCA I and hCA II, respectively.