An Effective Catalytic Hydroboration of Alkynes in Supercritical CO2 under Repetitive Batch Mode

A facile method for the synthesis of unsaturated organoboron compounds by hydroboration of terminal and internal alkynes in supercritical (sc) CO2 has been presented for the first time. The reactions performed in scCO(2) in the presence of Ru catalysts (selectivity, productivity) are compared with those in a traditionally used solvent or without it. Moreover, the catalytic systems based on the application of scCO(2) have been successfully tested for the processes under repetitive batch conditions. This strategy permitted us to obtain boryl-substituted olefins with high yields and selectivities up to the 16th catalytic cycle if using Ru(CO)Cl(H)(PPh3)(3) as a catalyst. The process applied the self-dosing catalyst, which is gradually released to the reaction mixture under supercritical conditions in the individual batch. Such an approach has a positive impact on process sustainability and economy.