A highly active phosphine-borane organocatalyst for the reduction of CO2 to methanol using hydroboranes

Article abstract of DOI:10.1021/ja404585p

In this work, we report that organocatalyst 1-Bcat-2-PPh₂-C ₆H₄ ((1); cat = catechol) acts as an ambiphilic metal-free system for the reduction of carbon dioxide in presence of hydroboranes (HBR₂ = HBcat (catecholborane), HBpin (pinacolborane), 9-BBN (9-borabicyclo[3.3.1]nonane), BH₃·SMe₂ and BH ₃·THF) to generate CH₃OBR₂ or (CH ₃OBO)₃, products that can be readily hydrolyzed to methanol. The yields can be as high as 99% with exclusive formation of CH ₃OBR₂ or (CH₃OBO)₃ with TON (turnover numbers) and TOF (turnover frequencies) reaching >2950 and 853 h^-1, respectively. Furthermore, the catalyst exhibits "living" behavior: once the first loading is consumed, it resumes its activity on adding another loading of reagents.