Rice straw ash extract, an efficient solvent for regioselective hydrothiolation of alkynes

Herein, we describe a simple and inexpensive protocol for the hydrothiolation of alkynes. In this context, water extract of rice straw ash (WERSA) has been proven to be a green, mild and efficient solvent for the preparation of vinyl thioethers. Generally, it was found that alkyne and thiol derivatives were excellent reaction partners, producing the corresponding products with good yields and good stereoselectivity with the predominant formation of the Z isomer. Moreover, WERSA was recovered and reused for further catalytic reactions without a significant loss of activity.