Introduction

Indanes are important class of molecules due to the pharmacological and medicinal properties [1–4] as well as natural product chemistry [5]. Brominations of hydrocarbons are important processes in synthetic chemistry [6–10]. The materials obtained from bromination of hydrocarbons have numerous industrial applications as pesticides, plastics, fire retardants and pharmaceutical chemicals [11]. Bromoindanes are important key intermediates in the industrial and laboratory preparation of hydroxy and epoxide compounds [12], and of indenone and fluorenone compounds [13].

In continuation of our investigations of the synthesis and structure of the bromoindanes, we describe herein the synthesis and structure of a new compound 2′,3′,3′-tribromo-2′,3′-dihydrospiro[1,3-dioxolane-2,1′-indene] (Scheme 1). In addition, a semiempirical quantum-mechanical calculation was carried out using the CNDO approximation. The theoretical CNDO and experimental X-ray structural results has been compared with each other.

Scheme 1
scheme 1

Synthesis of 2′,3′,3′-tribromo-2′,3′-dihydrospiro[1,3-dioxolane-2,1′-indene]

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Experimental

Synthesis

Melting points were determined on a Büchi model 530 apparatus and are uncorrected. 1H and 13C NMR spectra were recorded on 400 (100) MHz spectrometers. Mass spectra (EI) were recorded at 70 eV as m/z. All solvents were dried and distilled before use. Column chromatography was performed on silica gel 60 (70–230 mesh, Merck). TLC was carried out on Merck 0.2 mm silica gel 60 F254 analytical aluminium plates. The substance reported in this paper is in its racemic form.

To a magnetically stirred solution of starting material 3′-bromospiro[1,3-dioxolane-2,1′-indene] (100 mg, 0.4 mmol) in dichloromethane (2 ml) at room temperature was added, dropwise, a solution of bromine (70 mg, 0,44 mmol) in dichloromethane (0.5 ml) over the course of 1 min. After stirring for 10 min at room temperature, the solvent was evaporated and the crude product, 160 mg (98 %) of tribromide, was crystallized from ether/hexane (3:1). m.p. 380–382 K.

1H NMR (400 MHz, CDCl3): 7.78 (d, J = 7.7 Hz, Hz), 7.55 (td, J = 1.0 Hz, J = 7.7 Hz, 2H), 7.42 (td, J = 1.0 Hz, J = 7.7 Hz, 2H), 7.32 (d, J = 7.7 Hz, 2H), 5.06 (s, 2H), 4.47 (m, 2H), 4.37 (m, 2H), 4.29 (m, 2H), 4.22 (m, 2H). 13C NMR (100 MHz, CDCl3): 145.0, 136.2, 131.6, 131.1, 125.8, 122.9, 110.9, 70.5, 66.83, 66.78, 59.6. IR (KBr, cm−1): 2956, 2895, 1465, 1316, 1273, 1193, 1149, 1090, 1052, 1027, 966, 948.

X-Ray Structural Analysis

Crystallographic data are given in Table 1. Pale yellow block crystal (0.2, 0.2, 0.2 mm) was used for data collection. Diffraction data for the title compound were collected at room temperature (T = 294(2) K) using a Rigaku R-AXIS RAPID-S diffractomer with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The data were corrected for Lorentz-polarization and absorption effects using CrystalClear [14]. The structure was solved by the direct method using SIR97 [15] and was refined by full matrix least squares based on F 2 using SHELXL-97 [16]. The molecular graphic were drawn using the ORTEP-3 for Windows [17] and PLATON programs [18].

Table 1 Crystal data and experimental details
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H-atoms were positioned geometrically and refined using a riding model with C–H = 0.93 and 0.97 Å, and with Uiso(H) = 1.2 Ueq(C). All non-hydrogen atoms were refined anisotropically. Two poorly fitted reflections (4 9 0) and (7 2 0) were omitted from the refinement. The atoms, C1 and C2, of the –C–C– bond between the oxygen atoms in the 1,3-dioxolane ring, are disordered over two sites with site-occupancy factors of 0.62(7) and 0.38(7). In the final difference Fourier map, the highest peak is 0.86 Å from atom Br3 and the deepest hole is 1.05 Å from atom Br2.

Results and Discussion

Crystal Structure

As shown in the title compound, (Fig. 1), the cyclopentane ring (C4–C9) fused to the benzene ring of the nine-membered ring system (C3–C11) adopts an envelope conformation with C11 at the tip of the envelope [the puckering parameters [19] are Q(2) = 0.330(11) Å and ϕ(2) = 141.5(19)°].

Fig. 1
figure 1

Molecular structure and atomic numbering scheme for the title compound. Displacement ellipsoids for non-H atoms are drawn at the 30% probability level. Only the major components of the disordered 1,3-dioxolane ring are shown for clarity

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The C atoms of the CH2 groups of the 1,3-dioxolane ring, are disordered over two sites with an occupancy ratio of 0.62(7):0.38(7). In the disordered 1,3-dioxolane ring, its minor component adopts an envelope conformation with C3 at the tip of the envelope [the puckering parameters are Q(2) = 0.20(3) Å and ϕ(2) = 31(9)°].

In the title compound, the values of the C–Br bond lengths range from 1.915(10) to 1.972(10) Å. The relatively wide range of the Br–C–C bond angles are within the range 108.6(7)–116.2(7)° and this may indicate repulsion between the neighbouring Br atoms. In a related structure (1RS,2SR)-1,2,4,5,7-pentabromo-5-methoxyindane [9], the five Br–C distances vary from 1.884(7)° to 1.980(7)° Å. The Br–C–C angles are within the range 107.2(5)°–117.0(4)°. In trans,trans,trans-2,3,5,8-tetrabromo-1,4-dihydroxy-1,2,3,4-tetrahydronaphthalene [20], very similar values for the corresponding parameters [1.938(5)Å and 107.0(3)–121.6(4)°, respectively] were observed. All the bond lengths are within normal values (Table 1) [21].

In the crystal structure, the C–H···Br and C–H···O hydrogen bonding interactions (Table 2) help to stabilize the crystal packing of the title compound. Figure 2 shows the packing and hydrogen bonding in Table 3 of the title compound, along the a-axis.

Table 2 Selected geometric parameters (Å, °)
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Fig. 2
figure 2

View of the packing and hydrogen bonding of the title compound, along the a-axis. H atoms not involved in hydrogen bonding and the minor components of the disordered 1,3-dioxolane ring are omitted for the sake of clarity

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Table 3 Hydrogen-bond parameters (Å, °)
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Semiempirical CNDO Calculations

Theoretical calculations were carried out using the semiempirical quantum-mechanical complete neglect of differential overlap (CNDO) method [22]. The spatial view of the single molecule calculated as closed-shell in a vacuum is shown in Fig. 3 with atomic labels. When we compare the theoretical CNDO and experimental X-ray structural results with each other, it is shown that due to the intermolecular interactions in the crystal structure of the title compound, the spatial configurations obtained by the theoretical CNDO and experimental X-rays for the title compound are almost the same (see Figs. 1, 3, Table 2). We may state that the theoretical calculation (based on isolated molecules) of the title compound supports the suggestion that the present intra and intermolecular interactions in the title compound influence crystal packing. The HOMO and LUMO energy levels of the title compound are −4.1128 and 0.8545 eV, respectively. Its calculated molecule dipole moment is 8.507 Debye (1D = 3.33564 × 10−30 C.m.). The charges at atoms C10, C11, O1, O2, Br1, Br2 and Br3 are −0.3025, −0.3029, 0.0535, 0.1285, 0.2418, 0.1724 and −0.5880 e−, respectively.

Fig. 3
figure 3

The spatial view of the title molecule (I), calculated by the CNDO approximation

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Supplementary Material

CCDC 917443 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_resquest/cif.