A method to search the most stable reaction pathway and its application to the Pinner Pyrimidine Synthesis reaction

The development of synthetic routes for functional chemicals has been heavily depending on experience and intuition of synthetic organic chemists. In case that target molecules have complex structures, there are many possible synthetic routes, and it is often difficult to determine which one should be adopted. In order to decrease synthesis routes for experiments, we introduced “in silico screening” which requires to search TSs for synthesis routes, we have proposed a method to locate the new TS structure of a target reaction by using TS structures in TSDB. However, this method seldom gives the most stable TS structure within possible conformers. That is, the stability of transition states (TS), reactants and products is highly dependent on initial structures used for optimization. Therefore, this method is likely to give inadequate data to compare calculated and measured values of other synthetic reactions. For these purposes, we have to find reaction mechanisms with the most stable TS and molecules involved in the reactions. In this paper, we proposed a method to search the most stable reaction pathway and applied it to the Pinner Pyrimidine reaction of ethyl 3-oxobutanoate and 3-ethoxypropanimidamide.