3-Amino-5-(4-chlorophenylamino)-4-cyanofuran-2-carboxamide (2) was used as the key molecule for preparation of various furopyrimidines 3-9 and formation of spiro-cycloalkane furopyrimidines 10, 11. Also, poly fused heterocyclic compounds 13-17 were prepared from compound 2. The synthesized compounds were screened for their antimicrobial activity.

The title compound, C(23)H(20)N(4)O, is a heterocyclic phenyl-hydrazone Schiff base with a pyrazole moiety. In the crystal, a variety of inter-actions occur, including N-H⋯π and π-π stacking between the phenyl ring of the phenyl-hydrazinyl group and its symmetry-generated equivalent [centroid-centroid distance = 3.6512 (7) Å].

In the title compound, C(21)H(19)N(3)O(4), two intramolecular N-H⋯O hydrogen bonds generate two six-membered rings. The dihedral angles between the central heterocyclic ring and the two pendant rings are 61.5 (2) and 63.5 (1)°.

In the title compound, C(17)H(14)ClNO(2), the p-chloro-benz-yloxy residue assumes an E conformation with respect to the benzofuran system. The carbo- and heterocyclic systems make a dihedral angle of 47.99 (4)°. In the crystal, there are no significant intermolecular interactions present.

In the crystal structure of the title compound, C(11)H(11)NO(3)S, the mol-ecules are linked by inter-molecular C-H⋯O hydrogen-bond inter-actions. The heterocyclic thia-zine ring adopts a conformation inter-mediate between twist and boat.

The title compound, C(12)H(14)O(4), is an important inter-mediate in the synthesis of biologically active heterocyclic compounds. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules. There are also C-H⋯π contacts between the benzene ring and the methyl-ene groups.

In the title compound, C(20)H(18)ClN(3)O, the dihedral angle between the pyrazole and the 3H-indole components is only 13.28 (6)°, indicating that there is conjugation between the two heterocyclic subunits. The N-methoxy-phenyl unit makes a dihedral angle of 25.10 (7)° with the pyrazole ring.

In the title compound, C10H13NO2S, the heterocyclic ring adopts a half-chair conformation and the bond-angle sum at the N atom is 347.9°. In the crystal, inversion dimers linked by pairs of C-H⋯O hydrogen bonds generate R 2 (2)(8) loops.

The title compound, C(21)H(25)NO(2)S, consists of a five-membered heterocyclic ring, with pendant phenyl groups, an isopropyl group and a thio-ether residue. The thio-ether bonds to the heterocycle via the N atom. The absolute configuration results from an inversion of the configuration of substrate during the synthesis.

In the title compound, C(19)H(19)N(3)O(3)Se, the selenadiazole ring is essentially planar (r.m.s. deviation = 0.001 Å). The heterocyclic ring makes dihedral angles of 50.2 (2) and 76.3 (9)°, respectively, with the meth-oxy-phenyl and phenyl rings.