Crystal structure and Hirshfeld surface analysis of ethyl 2′-amino-5-bromo-3′-cyano-6′-methyl-2-oxospiro[indoline-3,4′-pyran]-5′-carboxylate

In the title structure, the 2,3-dihydro-1H-indole ring system is nearly planar, while the conformation of the 4H-pyran ring is close to a flattened boat. The mean planes of these fragments are approximately perpendicular to each other. In the crystal, the molecules are connected into layers by N—H⋯N and N—H⋯O hydrogen bonds.


Chemical context
The reactions that form C-C, C-N and C-O bonds play critical roles in various applications and in different fields of chemistry (Aliyeva et al., 2011;Zubkov et al., 2018;Viswanathan et al., 2019;Duruskari et al., 2020). Nitrogen heterocycles, especially those comprising indole fragments, are parts of various natural products and medicinal agents. This fragment constitutes the core of spiro-oxindole alkaloids, which exhibit a broad spectrum of biological activity (Edmondson et al., 1999;Ma & Hecht, 2004). The main synthetic pathway for the construction of spiro[4H-pyran-oxindole] compounds is based on three-component reactions ( Fig. 1) of two 1,3dicarbonyl (or other active methylene) compounds with isatin derivatives (Rad-Moghadam & Youseftabar-Miri, 2011).

Supramolecular features and Hirshfeld surface analysis
In the crystal, the molecules are linked by N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds, forming double layers parallel to (001) ( Table 1;  . In addition, C-HÁ Á Á interactions involving the centroids of the 4H-pyran and benzene rings link adjacent molecules within these layers (Table 1; Fig. 7). The layers are joined by van der Waals interactions ( The molecular structure of the title compound with the atom labelling and displacement ellipsoids drawn at the 50% probability level. Only the major position of Br1 [0.9676 (11)] is shown. Table 1 Hydrogen-bond geometry (Å , ).
A Hirshfeld surface analysis was performed to visualize the intermolecular interactions, and the accompanying twodimensional fingerprint plots were generated with Crystal-Explorer17 (Turner et al., 2017). Fig. 8 depicts the Hirshfeld surface plotted over d norm in the range À0.5859 to 1.4054 a.u. N-HÁ Á ÁN and N-HÁ Á ÁO contacts appear as red spots on the Hirshfeld surface.

Figure 5
The packing of the title compound viewed along the b axis and showing N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds.

Figure 6
The packing of the title compound viewed along the c axis and showing N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds.

Figure 7
A general view of the packing in the unit cell of the title compound with C-HÁ Á Á interactions shown as dashed lines.
In the crystal of I, the molecular conformation is maintained by an intramolecular C-HÁ Á ÁO interaction, generating a S(6) ring motif. The molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds into ribbons extending along the b-axis direction and consisting of R 2 2 (8) and R 2 2 (14) rings. Between the ribbons, there are weak van der Waals contacts.
In the crystal of II, the six-membered pyran ring adopts a conformation close to a flattened boat, as in the title structure. The molecules are joined by pairs of N-HÁ Á ÁN hydrogen bonds into dimers, those are linked by N-HÁ Á ÁO contacts to form ribbons along the a-axis direction.
In the crystal of III, the pyran ring is nearly planar. The molecules are joined by pairs of N-HÁ Á ÁN hydrogen bonds into centrosymmetric dimers, which are linked by N-HÁ Á ÁO contacts into ribbons along the c-axis direction.

Synthesis and crystallization
The title compound was synthesized using the reported procedure (Rad-Moghadam & Youseftabar-Miri, 2011), and colourless crystals were obtained upon isothermal recrystallization from an ethanol/water (3:1) solution.   Table 2 Summary of short interatomic contacts (Å ) in the title compound.

Figure 9
The

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. The Br1 and Br1 0 atoms connected to the C5 and C7 atoms have occupancy ratios of 0.9676 (11):0.0324 (11). EXYZ and EADP instructions were used to refine the positional and displacement parameters of C5, C7 and their counterparts C5 0 , C7 0 . The H atoms of the NH and NH 2 groups were located in a difference map, and their positional parameters were allowed to freely refine [N1-H1 = 0.88 (3), N8-H8A = 0.88 (3) and N8-H8B = 0.86 (3) Å ], but their isotropic displacement parameters were constrained to take a value of 1.2U eq (N). All H atoms bound to C atoms were positioned geometrically and refined as riding with C-H = 0.95 (aromatic), 0.99 (methylene) and 0.98 Å (methyl), with-U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for all others.