7-Amino-2-tert-butyl-5-methyl­pyrazolo[1,5-a]pyrimidine: a three-dimensional framework structure built from two N-H...N hydrogen bonds

The bond distances in the title compound, C₁₁H₁₆N₄, provide evidence for peripheral delocalization of [pi] electrons. The mol­ecules are linked by two independent N-H...N hydrogen bonds into a three-dimensional framework structure.

3-(3-Oxo-1,3-dihydro­isobenzofuran-1-yl­idene)pentane-2,4-dione

In the title compound, C₁₃H₁₀O₄, prepared by the condensation reaction between phthalic anhydride and pentane-2,4-dione, one of the acetyl groups in the pentane-2,4-dione fragment is almost coplanar with the isobenzofuran ring system, while the other group is twisted out of this plane by almost 80°. The corresponding C-C and C-O distances in the two acetyl units are consistent with dipolar delocalization into the coplanar unit only. There is no supra­molecular aggregation of the mol­ecules, but a number of rather short inter­molecular contacts of C-H...O, O...O and O...C types occur.

2,5-Dimethyl-6,7-dihydro­benzo[h]­pyrazolo[1,5-a]quinazoline and 2-tert-butyl-5-methyl-6,7-dihydro­benzo[h]pyrazolo[1,5-a]quinazoline

In both 2,5-dimethyl-6,7-dihydro­benzo[h]pyrazolo[1,5-a]­quinazoline, C₁₆H₁₅N₃, (I), and 2-tert-butyl-5-methyl-6,7-dihydro­benzo[h]pyrazolo[1,5-a]quinazoline, C₁₉H₂₁N₃, (II), which crystallizes with Z' = 2 in the space group P, the non-aromatic carbocyclic rings adopt screw-boat conformations. The mol­ecules of (I) are linked into chains of rings by a combination of C-H...N and C-H...[pi](arene) hydrogen bonds, while in (II) there are no hydrogen bonds of any kind.

8-tert-Butyl-7-(4-chloro­phen­yl)-10-phenyl-5,6-dihydro-10H-benzo[h]pyrazolo[3,4-b]quinoline

The title compound, C₃₀H₂₆ClN₃, crystallizes with Z' = 3 in the P space group. The three independent mol­ecules have very similar, although not identical, conformations, with almost perfect screw-boat forms adopted by the non-aromatic carbocyclic rings. Four independent C-H...[pi](arene) hydrogen bonds link the mol­ecules into centrosymmetric six-component aggregates.

(E)-3-{2-Amino-4-eth­oxy-6-[N-(4-meth­oxy­phen­yl)-N-methyl­amino]pyrimidin-5-yl}-1-phenyl­prop-2-en-1-one: a boat-shaped pyrimidine ring and a chain of hydrogen-bonded R⁴₂(8) and R²₂(20) rings

In the title compound, C₂₃H₂₄N₄O₃, the pyrimidine ring adopts an almost perfect boat conformation, and the bond distances provide evidence for some polarization of the mol­ecular-electronic structure. Two independent N-H...O hydrogen bonds link the mol­ecules into chains of edge-fused R²₄(8) and R²₂(20) rings.