Conformational preferences of 4-(para-substituted phenyl)2-isopropoxy-2,3-dihydropyran[2,3-c]pyrazoles: an example of dipole–dipole interaction

Abstract

A linear dependence between conformational free energy and dipole moments was observed for a series of 4–(para-substituted phenyl)-cis[2,4]- and trans[2,4]-2-isopropoxy-2,3-dihydropyran[2,3-c]-pyrazoles. The interaction is rationalized in terms of dipole–dipole interactions, and this is supported to a certain extent by CNDO/2 calculation of electron densities is model compounds.