A recyclable Ru(CO)Cl(H)(PPh₃)₃/PEG catalytic system for regio‐ and stereoselective hydroboration of terminal and internal alkynes

Abstract

Abstract This paper reports on the first repetitive batch selective hydroboration of terminal and internal alkynes in a series of poly(ethylene glycols) (PEGs), used as solvents and media for the immobilization of a Ru(CO)Cl(H)(PPh 3 ) 3 catalyst. The system based on 2 mol% of Ru−H complex and poly(ethylene glycol) with α‐methyl/ω‐trimethylsilyl ending groups (Mw=2000) was found to be the most efficient, and was able to carry out over 19 complete runs with the Z ‐addition of pinacolborane to the phenylacetylene. With the use of one portion of the developed catalytic system, the hydroboration of five different alkynes was performed consecutively, and led to five different products being obtained with high yields and purities. The developed strategy was characterized by high TON values and it was found to be the best recyclable protocol, leading to alkenyl boronates in all reported cases. magnified image