Modeling stereoselective reactions in solution

Abstract

In this study, ring-chain-ring tautomerization and asymmetric desymmetrization reactions are investigated by taking the solvent effect into account. In the first part, ring-chain-ring tautomerization mechanism is investigated by taking the effect of solvation into account in order to explain the enantiomeric interconversion of heterocyclic 2-oxazolidinone derivatives which are isolated as single enantiomers and have potential to be used as axially chiral catalysts. Density functional calculations reveal that there are two possible pathways with two different intermediary species which are amido and imino intermediates. This part of the study sheds light on the mechanistic details of both possible pathways to be able to understand and predict the ring-chain-ring tautomerization mechanism of similar heterocyclic systems. In the second part, the asymmetric desymmetrization mechanism is subjected to a computational analysis in an effort to investigate the alcoholysis of cyclic meso anhydrides in the presence of cinchona alkaloids. In the first step of this part of the study, the conformational analysis of cinchona alkaloids is carried out since the conformation plays a crucial role in enantioselectivity. Then, the mechanism of methanolysis of cyclic meso anhydrides catalyzed by cinchona alkaloids is considered by studying both stepwise and concerted pathways.