Istituto di Chimica Organica "Alessandro Marchesini", Facoltà di Farmacia, Università degli Studi di
Milano, Via Venezian 21, 20133 Milano, Italy
alessandro.contini@unimi.it
Received September 14, 2005
Abstract:
Benzopyranoimidazolones could virtually exist in four tautomeric forms, namely N3-H, N1-H, coumarin
O-H, and C2-H. Experimental evidence reported thus far has been unable to lead to a unique statement
about the preferred tautomeric forms in solution. In this work, tautomeric equilibria for a series of
2-substituted [1]benzopyrano[3,4-d]imidazol-4(3H)-ones were investigated by DFT calculations, in both
gas phase and solution. The influence of the solvent was included in the calculations by the CPCM
solvent model. 13C chemical shifts of all tautomers were computed at different levels of theory and then
compared with experiments to assign the preferred tautomers. Theoretical findings were then compared
to dynamic 1H NMR experiments results.
