Ru-Catalyzed Repetitive Batch Borylative Coupling of Olefins in Ionic Liquids or Ionic Liquids/scCO2 Systems

The first, recyclable protocol for the selective synthesis of (E)-alkenyl boronates via borylative coupling of olefins with vinylboronic acid pinacol ester in monophasic (cat@IL) or biphasic (cat@IL/scCO(2)) systems is reported in this article. The efficient immobilization of [Ru(CO)Cl(H)(PCy3)(2)] (1 mol%) in [EMPyr][NTf2] and [BMIm][OTf] with the subsequent extraction of products withn-heptane permitted multiple reuses of the catalyst without a significant decrease in its activity and stability (up to 7 runs). Utilization of scCO(2)as an extractant enabled a significant reduction in the amount of catalyst leaching during the separation process, compared to extraction withn-heptane. Such efficient catalyst immobilization allowed an intensification of the processes in terms of its productivity, which was indicated by high cumulative TON values (up to 956) in contrast to the traditional approach of applying volatile organic solvents (TON = similar to 50-100). The reaction was versatile to styrenes with electron-donating and withdrawing substituents and vinylcyclohexane, generating unsaturated organoboron compounds, of which synthetic utility was shown by the direct transformation of extracted products in iododeborylation and Suzuki coupling processes. All synthesized compounds were characterized using(1)H,C-13 NMR and GC-MS, while leaching of the catalyst was detected with ICP-MS.