Application of Molecular Mechanics Calculations to some Organic Reactions

This article describes the application of molecular mechanics calculation to the analysis of stereochemical outcome of some organic reactions using a semi-empirical transition state modeling. The combination of ab initio quantum mechanical calculations and molecular mechanics calculations was employed for the modeling the transition state. The modeling of the transition states of intramolecular [4+2] cycloaddition reaction of 14-membered carbocyclic triene has succeeded to predict the preferential formation of a single product with correct stereochemistries. Theoretical calculations can disclose the precise transition structure of a simple model system of [2,3] Wittig rearrangement. The obtained structure was then employed for further analysis and succeeded to predict the correct stereochemistry of the ring contraction product of the intramolecular [2,3] Wittig rearrangement of 13-membered diallyl ether. The stereochemistry of addition products of MeLi to ketone which is incorporated within a macrocyclic system is also mentioned