J. Heterocycl. Chem., 38, 1387-1391 (2001)

DOI: 10.1002/jhet.5570380622

A Density Functional Theoretical Study of the Influence of Cavities and Water Molecules on Tautomerism: the Case of Pyridones and 1,2,4-Triazoles Linked to Crown Ethers and Esters

The tautomerism of pyridones and 1,2,4-triazoles related to two crown ethers and two crown esters derived from these heterocycles was studied theoretically. For the four macrocycles, Bradshaw identified a single tautomer by X-ray crystallography. To rationalize these findings, a series of calculations from simple models to crown derivatives have been carried out. The most interesting case concerns the observation, for the first time, of a 4H-1,2,4-triazole tautomer. To explain this result it was necessary to calculate the whole crown ester plus a caged water molecule was necessary.