Rotation barriers around N-C=bond in some cyclic α,β-enaminoketones and α,β-enaminothioketones

Employing the method of complete analysis of the line shapes, we determined the activation parameters of the hindered rotation around the N-C=bond in 3-N, N-dimethylamino-5, 5-dimethyl-3-cyclohexene-1-thione, 3-N, N-dimethylamino-2-phenylindene-1-thione, and its oxygen analog. The values of the rotation barriers in the indene compounds are lower than in the cyclohexene derivatives, which can testify to a lower degree of p-π conjugation between the unshared electron pair of the nitrogen atom and the π electrons of the C=X (X=O, S) group in the indene ring.