IR spectra and structure of 6-methylimidazo[1,2-a]pyrimidine-2, 5-dione and its 3-ylidene derivatives
The structures of 6-R-7-methylimidazo[1,2-a]pyrimidine-2,5-diones and their 3-alkylidene and 3-arylidene derivatives were studied by IR spectroscopy. It was established that these compounds exist in the solid phase in the form of a mixture of tautomers. The most probable tautomers were identified. It is shown that the νC=O band of the imidazole fragment correlates with the σ parameters of the substituents in the arylidene grouping. The geometry of this grouping is discussed.