4-Phenyl-1-(prop-2-yn-1-yl)-1H-1,5-benzodiazepin-2(3H)-one

4-Phenyl-1H-1,5-benzodiazepin-2(3H)-one reacts in the presence of a concentrated aqueous solution of sodium hydroxide and a quaternary ammonium salt (as catalyst) in benzene (phase transfer catalysis) with propargyl bromide, affording the title benzodiazepine derivative, C18H14N2O. In the molecule, the mean plane of the propargyl substituent is almost perpendicular with that of the amide group [dihedral angle = 87.81 (8)°]. In the crystal, the molecules are linked by C—H⋯O and C—H⋯N interactions.

4-Phenyl-1H-1,5-benzodiazepin-2(3H)-one reacts in the presence of a concentrated aqueous solution of sodium hydroxide and a quaternary ammonium salt (as catalyst) in benzene (phase transfer catalysis) with propargyl bromide, affording the title benzodiazepine derivative, C 18 H 14 N 2 O. In the molecule, the mean plane of the propargyl substituent is almost perpendicular with that of the amide group [dihedral angle = 87.81 (8) ]. In the crystal, the molecules are linked by C-HÁ Á ÁO and C-HÁ Á ÁN interactions.
We are grateful to the Fundaçã o para a Ciê ncia e a Tecnologia (FCT, Portugal) for their general financial support, for the post-doctoral research grant No. SFRH/BPD/63736/ 2009 (to JAF) and for specific funding toward the purchase of the single-crystal diffractometer.

Comment
Benzodiazepine derivatives are an important class of heterocyclic compounds in the field of drugs, pharmaceuticals and synthetic organic chemistry (Bird, 1996;Wolff, 1996), as they show antiviral (Di Braccio et al., 2001), analgesic (Di Braccio et al., 1990), and antipsychotic (Kavita et al., 1988) activities. These compounds are used worldwide as anticonvulsant agents (Sieghart & Schuster, 1984) or as sedative or hypnotics Ahmed et al., 1983). Examples of well known diazepines are Alprazolam, Diazepam and Flunitrazepam (Wolff, 1996). Their pharmacological effects come from the activation of the benzodiazepine receptor which interacts with the GABA recognition site (Meldrum & Chapman, 1986). Research in this area is highly active being directed towards the synthesis of compounds with enhanced pharmacological activity. Following the research efforts from some of us concerning novel synthetic pathways of new benzodiazepines (Aatif et al., 2000;Baouid et al., 2001;Boudina et al., 2007), and our interest on the structural features of organic crystals (Fernandes et al., 2011;Amarante, Figueiredo et al., 2009;Paz & Klinowski, 2003;Paz et al., 2002), here we wish to report the synthesis via phase transfer catalysis and the crystallographic studies of the title compound (I).
The asymmetric unit is composed of a whole molecular moiety of I ( Fig. 1). All atoms are distributed over four medium planes (see Table 1 for details), which converge in the diazepine ring. The plane of the substituent aromatic ring is extended to the imine group from the diazepine moiety (plane A) and subtends an angle of 71.78 (4)° with the amide plane (C). The plane of the benzo ring (B) subtends, on the other hand, two almost similar angles with the previously described planes  Table 2 for details), namely the C-H and CH 2 groups of the propargyl moiety interact with N2 from the imine and O1 from the amide of neighbouring molecules, respectively.

Experimental
Melting points were taken in an open capillary tube on a Buchi 510 apparatus and are uncorrected. The FT-IR spectrum was obtained from KBr pellets using a Bruker Tensor 27 spectrophotometer. NMR Spectra were recorded with the following instruments: 1 H, Bruker AC-300; 13 C, Bruker AC-75. TMS was used as an internal reference. Mass spectra were recorded using a Jeol JMS DX 300 instrument. Column chromatography was carried out using E-Merck silica gel 60F 254 . All reagents were purchased from commercial sources and were used without further purification.
A mixture of 1 g (4.6 mmol) of II, 0.43 g (2.3 mmol) of benzyltriethylammonium chloride (TBA-Cl) and 3 ml of a 50% sodium hydroxide aqueous solution in benzene (25 ml) was stirred at ambient temperature. After 15 min, propargyl bromide was added slowly. After 6 h of stirring at 298 K, the reaction mixture was diluted with water (30 ml). The organic layer was extracted with benzene (3 × 10 ml), dried over anhydrous sodium sulfate and evaporated under vacuum. The title compound was isolated by column chromatography on silica gel using hexane/ethyl acetate as eluent. The solid product was

Refinement
Hydrogen atoms bound to carbon were placed at their idealized positions and were included in the final structural model in riding-motion approximation with C-H = 0.95 Å (aromatic and acetylenic), and C-H = 0.99 Å (aliphatic -CH 2 -). The isotropic thermal displacement parameters for these atoms were fixed at 1.2×U eq of the respective parent carbon atom. Fig. 1. Asymmetric unit of the title compound showing all non-hydrogen atoms represented as thermal ellipsoids drawn at the 50% probability level and hydrogen atoms as small spheres with arbitrary radii.