Crystal structure of 1′-(prop-2-yn-1-yl)-1,4-dihydrospiro[benzo[d][1,3]oxazine-2,3′-indolin]-2′-one

In the title compound, C18H14N2O2, the six-membered oxazine ring adopts a half-chair conformation and its mean plane makes a dihedral angle of 83.23 (7)° with the pyrrolidine ring of the indoline ring system. In the crystal, molecules are linked via N—H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by C—H⋯π interactions, forming slabs parallel to (001).


S1. Synthesis and crystallization
A mixture of N-propargylisatin (1.0 mmol), and 2-aminobenzylalcohol (1.0 mmol) was refluxed in ethanol, in the presence of InCl 3 (10 mol%), for 2 h. After the reaction was complete as indicated by TLC, the reaction mixture was cooled to room temperature. The solid that formed was filtered, dried and recrystallized in ethanol or dichloromethane to obtain in good yield (89%) of the pure title product as block-like colourless crystals.

S2. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The N-and C-bound H atoms were positioned geometrically (N-H = 0.86 Å, C-H = 0.93-0.97 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (N,C).

S3. Structural commentary
Spiro compounds represent an important class of naturally occurring substances, which in many cases exhibit useful biological properties (Kobayashi et al., 1991;James et al., 1991). 1,3-dipolar cycloaddition reactions are widely used for construction of spiro-compounds (Caramella & Grunanger, 1984). It has also been reported that spiro-oxazine derivatives have real or potential applications in many fields such as protection, decoration, display, memory, switches, photography, photometry and photomechanics (Chibisov & Görner, 1999). Efforts have been made to design this industrially and biologically active hetrocyclic compounds by making or breaking carbon-carbon (C-C) and carbon-hetero atom (C-X) (Kamalraja et al., 2014). This InCl 3 -mediated compound have been synthesized as a part of the effort carried to develop eco-friendly potential compound by new synthetic method.
The molecular structure of the title compound is illustrated in Fig 1. The oxazine ring (O1/N1/C7/C8/C9/C14) adopts a half chair confirmation, and its mean plane makes a dihedral angle of 83.23 (7) ° with the pyrrolidine ring (O1/N1/C8/C9/C14) of the indolinone ring system. The indole ring system is essentially planar, with atoms C16 and O2 deviating from its mean plane by -0.0130 and 0.0273 Å, respectively. The dihedral angle between the benzene ring (C1-C6) of the indoline ring system and the benzene ring (C9-C14) of the mean plane of the 2,4-dihydro-1H-benzo  The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The crystal packing of the title compound, viewed along the c axis. Hydrogen bonds are shown as dashed lines (see Table   1 for details).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (7)  C15 0.0260 (7) 0.0342 (7) 0.0321 (7) −0.0102 (6) 0.0018 (6) 0.0012 (6)  C8 0.0350 (8) 0.0468 (9) 0.0310 (7) −0.0155 (7) 0.0041 (6) −0.0023 (6)  C10 0.0388 (9) 0.0531 (9) 0.0352 (8) −0.0096 (7) 0.0022 (7) −0.0084 (7)  C1 0.0317 (7) 0.0305 (7)