Beugungseffekte in gespannten Cyclohexanderivaten

Abstract

The flexional, reflexional and inversion properties of some derivatives of constrained cyclohexanes are described. In the case of the nopinols, isonopinols and pinocamphols, it is seen that in general the gem-dimethylcyclohexane ring prefers a flattened chair conformation except when there is a severe non-honded interaction between ring substituents and the gem-dimethyl grouping. Moreover it appears that the so-called reflex effect springs mainly from the pinching together of the C₁ and C₅ atoms which leads in turn to a flattening of the chair conformation.
Substituent effects on the ring inversion process of the gem-difluorocyclohexane chair conformation are also described. The syn-axial methyl-fluorine interaction has a negligible effect on the rate of inversion, whereas the syn-axial methyl-methyl interaction has an appreciable effect.