Chemical properties of ylidene derivatives of azines. 1. Structure of the products of protonation of dihydro-2-pyrimidylidene- and dihydro-4-pyrimidylidenecyanoacetic esters
The structure of the products of protonation of dihydro-2-pyrimidylidene- and dihydro-4-pyrimidylidenecyanoacetic esters was investigated by means of IR, UV, and 1H and 13C NMR spectroscopy. It is shown that, in contrast to the corresponding α-derivative of pyridine. the investigated compounds have an ylidene structure in solutions of strong acids and in the form of perchlorates; the protons are attached to the heterocyclic nitrogen atoms.