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In the title compound, C18H16N2O2S, the 5-dihydroisoxazol-5-yl ring and its phenyl substituent are nearly coplanar, with the largest deviation from the mean plane being 0.0184 (16) Å. The thiomorpholin-3-one ring adopts a screw-boat conformation and the attached benzene ring makes a dihedral angle of 42.26 (7)° with the mean plane through the 3-phenyl-4,5-dihydroisoxazol-5-yl ring system. In the crystal, molecules are linked by pairs of C—H...N hydrogen bonds, forming inversion dimers. These dimers are linkedviaC—H...O hydrogen bonds, generating a three-dimensional network.

The title compound, C19H22O2, was synthesized in three steps from a mixture of α-, β- and γ-himachalene, which was isolated from an essential oil of the Atlas cedar (Cedrus atlantica). In the crystal, molecules are linked by C—H...O hydrogen bonds into chains running parallel to thebaxis.

À, is approximately planar, with the pyridine and pyridinium rings being inclined to the central thiadiazole ring by 6.51 (9) and 9.13 (9) , respectively. The dihedral angle between the pyridine and pyridinium rings is 12.91 (10) . In the crystal, the cations are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, involving the perchlorate anion, forming chains propagating along the [100] direction. The chains are linked by weak offset -interactions [inter-centroid distance = 3.586 (1) Å ], forming layers parallel to the ab plane. Structure descriptionTransition metal complexes with the ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole (L) have attracted considerable attention owing to their magnetic properties (Klingele et al., 2010) and biological activity (Zine et al., 2016). Indeed, the ligand (L) can coordinate to different metal ions in many modes (Bentiss et al., 2002(Bentiss et al., , 2011Ahmed et al., 2015;Laachir et al., 2013Laachir et al., , 2015a. However, we observed the formation of the title compound with the same ligand after the addition of perchloric acid, as a result of the proton donor-acceptor reaction between perchloric acid and 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole (L). In this case, no metallic salt was used.The structure of the title molecular salt is shown in Fig. 1. The cation is almost planar with the pyridine (N1/C1-C5) and pyridinium (N4/C8-C12) rings being inclined to the central thiadiazole (S1/N2/N3/C6/C7) ring by 6.51 (9) and 9.13 (9) , respectively. The dihedral angle between the pyridine and pyridinium rings is 12.91 (10).

All the non-H atoms of the title compound, C 15 H 17 NO 2 , except the CH 3 groups of the isopropyl unit and the O atoms of the nitro group, lie on a crystallographic mirror plane. The dihedral angle between the naphthalene plane and the nitro group is constrained to be 90 by symmetry. In the crystal, molecules are linked by -interactions [centroid-centroid separation = 3.6591 (4) Å ] and stacked along the b-axis direction. Structure descriptionThe bicyclic sesquiterpenes -and -himachalene are the main constituents of the essential oil of the Atlas cedar (Cedrus atlantica) (Benharref et al., 2015;Loubidi et al., 2014). As part of our ongoing studies of such systems (Benharref et al., 2016), we now report the synthesis and crystal structure of the title compound.The molecular structure of the title compound is illustrated in Fig. 1. The naphthalene ring system is perfectly planar (all atoms lie on a crystallographic mirror plane). The O atom of the nitro group (N1/O1/O1a) and the isopropyl group (C13/C13a) lie perfectly normal to the mean plane of the naphthalene moieties with the same dihedral angle of 90 . In the crystal, molecules are linked through -interactions between naphthalene ring systems stacked along b axis, as shown in Fig. 2, the intercentroid distance being 3.6591 (4) Å . Synthesis and crystallizationIn a reactor of 250 ml volume equipped with a magnetic stirrer and a dropping funnel, were introduced 60 ml of dichloromethane, 3 ml of nitric acid and 5 ml of concentrated

In the title compound, C15H10BrNO2, the indoline ring system, the two ketone O atoms and the Br atom lie in a common plane, with the largest deviation from the mean plane being 0.073 (1) Å for the Br atom. The fused-ring system is nearly perpendicular to the benzyl ring, as indicated by the dihedral angle between them of 74.58 (10)°. In the crystal, molecules are linked by weak C—H...O hydrogen bonds and by π–π interactions [inter-centroid distance = 3.625 (2) Å], forming a two-dimensional structure.