Theoretical modeling of the interaction chiral modifier/substrate as a key step in the enantioselective hydrogenation of α-ketoesters and vicinal diketones

Abstract

This paper deals with the computational modeling of the chiral modifier/substrate interaction for chiral modifiers studied in our laboratory, different from those conventionally used in enantioselective hydrogenation reactions. (S)- (+)-1-Aminoindane and (R)-(-)-1-aminoindane were chosen as chiral modifiers and the selected substrates were methyl pyruvate, ethyl pyruvate and 1-ethyl-4,4-dimethyl-pyrrolidin-2,3,5-trione. The geometry of each of the chiral modifier/substrate complexes was optimized using DFT calculations and a BLYP functional. The theoretical enantiomeric excess was calculated from the energy of each of the proposed complexes. The calculations were carried out considering different reaction solvents through the use of COSMO program. It was found that this simple model allows predicting the experimental values of both the sense of enantiodifferentiation and the enantiomeric excess with a good approximation. It was also able to predict the inversion of configuration when using the (S)-(+)-1-aminoindane as chiral modifier in polar solvents such as acetic acid and 2-propanol.