Studies in nitrosopyrazoles .1. Preparative and spectroscopic studies of some 3,5-dialkyl-4-nitrosopyrazoles

The preparations of a number of 3,5-disubstituted- and 1,3,5-trisubstituted-4-nitrosopyrazoles are described and a range of physical properties of these compounds are measured. Comparison is made with some 2,6-disubstituted nitrosobenzenes and it is shown from C-13 NMR spectroscopy that the effects of substitution by flanking tert-butyl groups are moderated in the case of the pyrazoles from those in the aromatic Cg ring due to a lessening of steric hindrance. It is also suggested that steric effects are evident in the preparation of 1,3,5-substituted-4-nitrosopyrazoles when one of the flanking groups to the Nd is tert-butyl or phenyl, there being no such effect for the corresponding case of the isobutyl group.