Synthetic and theoretical investigation on nano‐Au/TiO2 catalyzed hydrothiolation for construction of C─S bond: Experimental and DFT study

Abstract

AbstractIn this article, we describe a new synthetic and theoretical approach for the construction of C─S bond in heterocyclic molecules undergoing nanogold catalytic hydrothiolation reaction. The experimental studies showed that the reaction proceeded via regioselective Michael‐type anti‐addition and gave the corresponding sulfur bridged 1,3,4‐oxadiazole‐propenone in excellent yield. The compounds were characterized by analytical and spectral techniques. A gas phase molecular modeling study of nanogold‐catalyzed hydrothiolation of acetylenic ketone with 5‐aryl‐1,3,4‐oxadiazol‐2‐thiol was carried out using density functional theory (DFT) calculations. It showed the adsorption of acetylenic ketone on nanogold and preferable coordination at the β carbon of the alkyne group. The charge calculations showed that on adsorption over nanogold, the alkyne group became more polar in nature. The frontier highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analysis showed a possible overlap of molecular orbitals between thiol and acetylenic β carbon to give Z isomer. The experimental and theoretical validation of bond parameters was carried out. A possible mechanism of hydrothiolation reaction was proposed based on the analogy with the results of theoretical calculations and experimental evidence.