The effect of chirality of adjacent atoms of the carbene carbon of NHC organocatalyst on the stereoselectivity of the nucleophilic addition: a computational study

Stereoselectivity is an important concept in chemistry and biochemistry. Stereoselectivity can influence both of the biological activities and the interaction of drug-drug[1]. In other words, two enantiomers of a compound show very different characteristics. Therefor it is important to have a deep understanding about the efficiency of products in stereoselective reactions. N-heterocyclic carbene (NHC) is an organocatalyst that frequently used in the synthesis of asymmetric compound [2]. In this work, nucleophilic addition of a chiral NHC with two different enantiomers (A, B) and enal is investigated by computational method at DFT M062x/6-31g(d, p) with the solvent effects of 1,4 dioxane to shed light on the effect of chirality of adjacent atoms of carbene carbon of NHC on the chirality of product in nucleophilic addition of NHC to enal[3]. The calculated results show that for enantiomer A, the energy barrier via Si-face is higher than Re-face about 3.07 Kcal/mol while for enantiomer B, that the chirality of adjacent atoms of carbenecarbon of NHC is inversed to the above case, the energy barrier of Re-face is higher than Si-face. Thus, according to the calculatedresults, we can conclude that the chirality of adjacent atoms of the carbene carbon of NHC has a direct influence on the determinationof the chirality of products.

Keywords:

N-heterocyclic carbene , Stereoselectivity , Chirality