3-(2-Oxo-2,3,4,5-tetra­hydro­furan-3-yl)-1-benzofuran-2-carbonitrile

The asymmetric unit of the title compound, C₁₃H₉NO₃, consists of two crystallographically independent mol­ecules. In each mol­ecule, the tetra­hydro­furan (THF) ring adopts an envelope conformation with one of the methyl­ene C atoms positioned at the flap. The dihedral angles between the mean plane of the THF and the benzofuran ring system are 70.85 (5) and 89.59 (6)°. In the crystal, mol­ecules are stacked in a column along the a-axis direction through C—H...O hydrogen bonds, with columns further linked by C—H...N and C—H...O inter­actions.

A triclinic polymorph of 4-cyano­pyridinium hydrogen chloranilate

The asymmetric unit of the triclinic polymorph of the title compound (systematic name: 4-cyano­pyridinium 2,5-dichloro-4-hy­droxy-3,6-dioxocyclo­hexa-1,4-dien-1-olate), C₆H₅N₂⁺·C₆HCl₂O₄⁻, consists of two crystallographically independent cation–anion units, in each of which the cation and the anion are linked by an N—H...O hydrogen bond. In the units, the dihedral angles between the cation and anion rings are 78.43 (11) and 80.71 (11)°. In the crystal, each unit independently forms a chain through N—H...O and O—H...N hydrogen bonds; one chain runs along the c axis while the other runs along [011]. Weak C—H...O, C—H...N and C—H...Cl inter­actions are observed between the chains.

10′-Chloro-3′,4′-dihydro-2′H-spiro­[cyclo­propane-1,7′(6′H)-pyrimido[2,1-a]isoquinolin]-6′-one

In the title compound, C₁₄H₁₃ClN₂O, the fused hydro­pyrimidine ring adopts an envelope conformation with one of the methyl­ene C atoms at the flap. The three-membered ring is approximately perpendicular to the attached isoquinoline ring system, with a dihedral angle of 89.44 (11)°. In the crystal, mol­ecules are linked by a weak C—H...π inter­action, forming a helical chain along the c axis.