Hydroacylation is a useful synthetic method, allowing an aldehyde and alkene to form a ketone. Experimental research has shown that rhodium catalyzed hydroacylation of vinyl benzaldehyde follows strict substitution effects. The mechanism of this reaction with the Rh(I)-DTBM-SEGPHOS catalyst was computationally determined using the M06L density functional with 6-31G(d) on nonmetal atoms and SDD basis set and effective core potential for rhodium for optimization. Single point solvent calculations were performed using the M05-2X functional and the SMD implicit solvent model with THF. Single point energy calculations were performed with the M05-2X functional and the 6-311+G(2d,p) basis set. When the alkene is a cyclopentene ring, no product is formed; however, when the alkene is cyclohexene, product is formed with high yield. The transition state between intermediates two and three shows a 3.0 kcal/mol barrier height for cyclohexene, and a 6.4 kcal/mol barrier height for cyclopentene, explaining the experimental difference in reactivity. Computational results predict the trans-product to be formed, but experimental results show epimerization of trans-product to cis-product under reaction conditions. The mechanism of epimerization is being investigated computationally.

Substitution effects in rhodium-catalyzed intramolecular hydroacylation

251st National Meeting (2016)

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