Catalyzed Chemoselective Acrolein Hydrogenation. Density Functional Studies

The catalytic chemoselective hydrogenation of C O and C C bonds of acrolein by HCo(CO) 3 has been investigated at the B3LYP density functional level of theory. For the C O hydrogenation to allyl alcohol, it is found that the reaction path with the allyloxy intermediate is more favored than the alternative path with the hydroxyallyl intermediate both kinetically and thermodynamically. For the C C hydrogenation to propanal, the reaction path of the hydride transfer to C β is more favored than to C α by the lower barrier of the Co−H insertion and the overall lower free energy barriers. The larger stability of the π complex HCo(CO) 3 (η 2 -H 2 C CHCHO) determines the C C chemoselectivity. Thus, propanal is the expected principal product, while the formation of allyl alcohol is almost suppressed, in line with the experimental finding.