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

Abstract

Four new salts of benzimidazolium andbis(benzimidazolium)which include coumarin or benzoxazinone moieties weresynthesized and the structures of the newly synthesized compounds were elucidated on the basis ofspectral analyses such as1H-NMR, 13C-NMR, HSQC, IR, LC-MS and elemental analysis. Benzimidazoliumsalts 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 andinhibition effectsof the synthesized compoundson human carbonic anhydrases(hCA)were investigated as in vitro. The in vitro results demonstratedthat all compounds inhibitedhCA I and hCA IIactivity.The inhibitory effects of the synthesized compounds on the hydratase and esterase activities of these isoenzymes (esterase activity is for hCA I) were studied in vitro.In relation to these activities, the inhibition equilibrium constants (Ki) were determined. The results showed that coumarin based benzimidazolium and bisbenzimidazolium salts are more active than benzoxazinones derivatives.