3-Hy­droxy-2,2-bis­(1H-pyrazol-1-yl)­cyclo­penta­none

The title compound, C₁₁H₁₂N₄O₂, was unexpectedly obtained in the reaction of α,α′-disubstituted cyclo­penta­none with 1,1,3,3-tetra­meth­oxy­propane in the presence of dioxane saturated with HCl. It belongs to a previously unknown class of gem-bihetaryl ketones which may be useful for screening of new substances with biological activity. In the studied structure, the cyclo­penta­none moiety adopts an envelope conformation, with the hy­droxy-bearing C atom as the flap [deviation from basal plane = 0.643 (3) Å]. The dihedral angle between the two pyrazole rings is 80.02 (8)°. In the crystal, inversion dimers are formed via a pair of O—H...N hydrogen bonds.

(1R,3R,3aS,8aR)-4-Oxo-3-phenyl-1-[(1R)-1-phenyl­eth­yl]deca­hydro­cyclo­hepta­[b]pyrrol-1-ium bromide

The title chiral compound, C₂₃H₂₈NO⁺·Br⁻, was obtained from an optically active amino­ethanol precursor. The pyrrolidine heterocycle has an envelope conformation, with the C atom α-positioned with respect to the keto group deviating by 0.570 (6) Å from the mean plane of other atoms. The trans-fused seven-membered ring adopts a pseudo-chair conformation. The two phenyl rings form a dihedral angle of 85.1 (2)°. The cationic center and the bromide anion are connected through an N—H...Br hydrogen bond.