One-pot tandem conversion of alkenes into 1,2-diols over efficient bifunctional tin-tungsten oxide catalysts

Tandem catalysis reaction, which integrates two consecutive steps into a single one, can efficiently eliminate the separation of intermediate products, shortening the reaction time and decreasing energy expenditure. Therefore, the development of an efficient method for catalyzing tandem conversion of alkenes to prepare 1,2-diols is extremely fascinating. In this work, we reported the hydrothermal synthesis of tin-tungsten oxide catalysts at different pH values and their application as bifunctional catalyst for the one-pot tandem catalysis of alkenes to 1,2-diols. The SnWO₄ catalyst prepared at pH = 5 revealed the best tandem conversion performance and could attain a 95.4 % of cyclohexene conversion as well as a 77.2 % of 1,2-cyclohexanediol selectivity within 4 h of reaction. A possible mechanism corresponding to the tandem catalytic conversion of cyclohexene into 1,2-cyclohexanediol over SnWO₄ catalyst was proposed. Moreover, quenching experiments, density functional theory (DFT) calculations and in-situ infrared characterizations were further utilized to verify the reaction mechanism. Sn(II) could stabilize tungstate through the formation of W-O-Sn bonds and effectively reduced the energy of tungsten active centre binding to hydrogen peroxide, promoting the tandem catalysis reaction of cyclohexene to 1,2-cyclohexanediol. In addition, the one-pot tandem catalysis system could be further extended to the majority of linear and cyclic alkene substrates. This work can give a basis for the development of more green and efficient tandem conversion reaction of alkenes into 1,2-diols.