N\u3csup\u3e1\u3c/sup\u3e-Acetyl-3\u27-methylandrosta-4,16-dieno[16,17-\u3cem\u3ed\u3c/em\u3e]pyrazole-3-one

In an attempt to find the structural features promoting the thermal isomerization of the N-acylated steroid [16,17-d]pyrazoles into [17,16-c]pyrazole derivatives,the X-ray structure analysis of the title compound, C23H30N2O3, (1), has been carried out. The steroid moiety of (I) has the usual conformation. The dihedral angle between the planar pyrazole ring and the N-acetyl group is very small [5.6 (2)°], but the amide C-N bond seems to be substantially elongated [1.404 (3) Å ]. The d-pyrazole ring junction via a double bond leads to deformations of some bond and torsion angles, which would be decreased in the case of a ring junction via a single bond in the [17, 16-c]pyrazole isomer