Tautomerism of hydroxychromenopyrazoles

Annular tautomerism (OH⋯N and/or NH⋯O) of hydroxychromenopyrazoles was studied by NMR-spectroscopy and B3LYP/6-311++G(d,p) theoretical calculations. The experimental chemical shifts of 4,4-dimethyl-7-pentyl-2,4-dihydrochromeno[4,3-c]pyrazol-9-ol have been compared with absolute shieldings calculations performed using the GIAO approximation. This study shows that the title compound exists mainly as an OH⋯N tautomer in solution. © 2012 Elsevier B.V. All rights reserved.Peer Reviewe