One-pot synthesis of alcohols from olefins catalyzed by rhodium and ruthenium complexes

The one-pot synthesis of butanol and heptanol from propene and I-hexene, respectively, was performed using Ru-3(PPh3)Cl-2 and Rh(CO)(2)(acac) in the presence of triphenylphosphene. The effects of various reaction parameters, including catalyst concentration, gas partial pressures, and temperature, were investigated. Two methods for performing the one-pot synthesis were developed and are discussed. In the first method, stoichiometric quantities of CO and propene or 1-hexene were fed to the autoclave. It was found that residual carbon monoxide necessary for the hydroformylation poisoned the Ru catalyst used for the hydrogenation. Venting the hydroformylation gases was therefore necessary for hydrogenation of the aldehyde to proceed. In the second method, sub-stoichiometric quantities of CO relative to olefin were fed to the autoclave, and CO conversion was driven to nearly 100%. In this case, the low residual CO concentration allowed the hydrogenation to proceed readily. The optimal temperatures and gas pressures for the hydroformylation were not the optimal temperatures and pressures for the hydrogenation. A strategy is described for maximizing the performance of both steps. Under optimal conditions, 100% conversion of propene to butanol could be achieved with 97% selectivity, and 99% conversion of 1-hexene to hepatanol could be achieved with 98% selectivity. The only byproduct observed in the latter case was a small amount of 2-hexene, which did not undergo hydroformylation. A possible reaction mechanism is proposed for both the hydroformylation of the olefin and the hydrogenation of aldehyde based on spectroscopic evidence. (C) 2009 Elsevier B.V. All rights reserved.