Correlation of the Experimental and Theoretical Study for the Cyclisation Reaction of Mesoionic Heterocycle Imidazo[1,5 A] Pyridines in Terms of the Density Functional Descriptors

Recently, Roy et al., published the synthetic procedure of biologically active mesoionic heterocycles. They have observed a peculiar mechanistic feature that substituted mesoionic derivatives do not undergo cyclisation whereas the unsubstituted one readily participates into the cyclisation. It is also revealed from their experimental study that sulphur containing mesoionic heterocycles are less reactive as compared to the oxygen containing derivatives. In this report, we have evaluated theoretical DFT based local reactivity parameters like fukui functions, local softness and local philicity indices to validate the above mentioned experimental facts. We have also calculated the global reactivity parameters to explain the reactivity differences between the substituted and unsubstituted mesoionic derivatives. The nice correlation between the experimental and theoretical counterpart supports our venture.