Regioselective Hydroformylation of Butadiene:  Density Functional Studies^†

The HCo(CO)₃-catalyzed hydroformylation of butadiene has been investigated at the B3LYP density functional level of theory. It is found that butadiene hydroformylation favors the formal 1,4-addition product in high regioselectivity. The enhanced stability of the syn-η³-allyl complex ((η³-CH₂CHCH(CH₃))Co(CO)₃) presents a distinctly thermodynamic preference for the Markovnikov insertion, and the following CO addition favors forming the 1,4-addition intermediate over the branched intermediate both kinetically and thermodynamically. Neither linear nor branched 1,2-addition product is favored. These results agree perfectly with the experimental findings. Furthermore, it is shown that methanol as solvent does not change the mechanistic picture significantly.