rac-(2aS,2a1R,3aR,3a1S,5aS,6aR)-2a-Allyl-2,4-di­chloro-2a,2a1,3a1,5a,6,6a-hexa­hydro-3aH-3-oxadi­cyclo­penta­[cd,gh]penta­len-3a-ol

Kotha, S.; Ansari, S.; Gupta, N.K.

doi:10.1107/S2414314621012608

organic compounds

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ISSN: 2414-3146

Volume 6| Part 12| December 2021| x211260

https://doi.org/10.1107/S2414314621012608

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rac-(2aS,2a¹R,3aR,3a¹S,5aS,6aR)-2a-Allyl-2,4-dichloro-2a,2a¹,3a¹,5a,6,6a-hexahydro-3aH-3-oxadicyclopenta[cd,gh]pentalen-3a-ol

Sambasivarao Kotha,^a ^* Saima Ansari ^a and Naveen Kumar Gupta ^a

^aDepartment of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India
^*Correspondence e-mail: srk@chem.iitb.ac.in

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 8 October 2021; accepted 26 November 2021; online 16 December 2021)

The title racemic triquinane, C₁₄H₁₄Cl₂O₂, is composed of four five-membered rings, one of which is a tetrahydrofuran ring to which an allyl group on one side and a hydroxyl group on the other side are attached. The core of the triquinane unit has a cis–syn–cis configuration. In the crystal, the molecules are linked by pairwise O—H⋯O hydrogen bonds, generating inversion dimers featuring R²₂(8) loops.

Keywords: crystal structure; triquinane; hemiketal; indium-catalysed; transannular cyclization.

CCDC reference: 2114309

Structure description

Compounds with three fused five-membered rings, known as triquinanes, have gained considerable importance because this core is found in several biologically active compounds (Qiu et al., 2018 ; Kotha et al., 2020 ). Therefore, convenient methods to prepare and functionalize triquinanes and the study of their stereochemistry are useful exercises (Mehta & Rao, 1985 ). Our group has prepared triquinanes from cage compounds in a simplified manner using microwave irradiation (Kotha et al., 2019 ). Thereafter, we attempted to functionalize the triquinanes and observed a transannular attack at the keto centre (O1—C1—O2) leading to the formation of the title compound, 1.

Compound 1 has three carbocyclic rings (C1/C2/C3/C4/C5, C4/C5/C6/C7/C8 and C6/C7/C9/C10/C11) and a terahydrofuran ring (O1/C1/C5/C6/C11). The allyl group is unsymmetrically substituted at C11 and the hydroxy group is attached to C1 (Fig. 1a). There are six stereogenic centres in 1: in the arbitrarily chosen asymmetric molecule, the configurations are C1 R, C4 R, C5 S, C6 R, C7 S and C11 S but crystal symmetry generates a racemic mixture.

Figure 1
The molecular structure of 1 (a) viewed from above and (b) viewed from the front. Displacement ellipsoids are drawn at the 50% probability level.

The triquinane ring system consists of a cis–syn–cis configuration, i.e., the hydrogen atoms at the ring junction are all above the plane and the first and the third rings are below the plane (Fig. 1b). The chlorine atoms are attached to the unsaturated bonds C2—C3 and C9—C10 in anti-manner with respect to the H atoms of the ring junction. The middle cyclopentyl ring adopts an envelope conformation and the side rings are almost planar.

In the crystal, the molecules are linked by O—H⋯O hydrogen bonds, generating inversion dimers featuring R₂²(8) loops (Table 1, Fig. 2) but no intramolecular hydrogen bonds are present.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O1ⁱ	0.84	2.06	2.893 (3)	173
Symmetry code: (i) .

Figure 2
The crystal packing of 1, viewed along the b-axis direction. The hydrogen bonding is shown using dotted lines.

Synthesis and crystallization

The synthesis scheme is shown in Fig. 3. Indium ingots (51 mg, 2.7 eq) were cut into small pieces and transferred to a two-neck round-bottomed flask. Tetrahydrofuran (3 ml) was transferred to the flask under nitrogen at room temperature. Allyl iodide (0.5 ml) was added to this solution via a syringe. After one h, the starting material 2 (40 mg) and trimethylchlorosilane (3 drops) was added to the reaction mixture. On completion of the reaction (TLC monitoring) after 1 h, water was added to the reaction mixture. The aqueous layer was extracted with diethyl ether (Lee et al. 2001 ). The compound was purified with column chromatography and silica gel (100–200 mesh) was used. Ethyl acetate:petroleum ether (8% of ethyl acetate in total in 100 ml of solution) was used an eluent. After that, the crystals suitable for X-ray crystallographic analysis were grown in air in a glass vial using ethyl acetate as solvent (Fig. 3).

Figure 3
Synthesis scheme for 1.

Characterization: colourless crystalline solid; m.p. 120–122°C; ¹H NMR (500 MHz, CDCl₃): δ = 5.73–5.62 (m, 3H), 5.20–5.14 (m, 2H), 3.39–3.30 (m, 2H), 3.23–3.20 (m, 1H), 3.02–2.98 (m, 1H), 2.63 (dd, J = 13.8, 7.0 Hz, 1H), 2.55 (dd, J = 13.8, 7.0 Hz, 1H), 1.95–1.87 (m, 1H), 1.78 (d, J = 13.9 Hz, 1H) p.p.m.; ¹³C NMR (125 MHz, CDCl₃): δ = 134.1, 133.2, 133.1, 133.0, 132.5, 119.1, 115.5, 97.7, 58.8, 54.8, 47.7, 46.4, 40.4, 35.2 p.p.m.; HRMS (ESI): m/z calculated for C₁₄H₁₄Cl₂NaO₂ [M + Na]⁺: 307.0262; found: 307.0263.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₄H₁₄Cl₂O₂
M_r	285.15
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	150
a, b, c (Å)	7.2687 (10), 8.3648 (11), 11.7460 (18)
α, β, γ (°)	80.448 (4), 83.441 (4), 65.285 (4)
V (Å³)	638.96 (16)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.50
Crystal size (mm)	0.32 × 0.29 × 0.09

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2016 )
T_min, T_max	0.655, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	19764, 2241, 1662
R_int	0.106
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.107, 1.09
No. of reflections	2241
No. of parameters	164
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.33
Computer programs: APEX2 and SAINT (Bruker, 2016), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Structural data

CCDC reference: 2114309

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314621012608/hb4394sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314621012608/hb4394Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: ShelXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

rac-(2aS,2a¹R,3aR,3a¹S,5aS,6aR)-2a-Allyl-2,4-dichloro-2a,2a¹,3a¹,5a,6,6a-hexahydro-3aH-3-oxadicyclopenta[cd,gh]pentalen-3a-ol top

Crystal data top

C₁₄H₁₄Cl₂O₂	Z = 2
M_r = 285.15	F(000) = 296
Triclinic, P1	D_x = 1.482 Mg m⁻³
a = 7.2687 (10) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.3648 (11) Å	Cell parameters from 3239 reflections
c = 11.7460 (18) Å	θ = 2.7–25.0°
α = 80.448 (4)°	µ = 0.50 mm⁻¹
β = 83.441 (4)°	T = 150 K
γ = 65.285 (4)°	Plate, clear light colourless
V = 638.96 (16) Å³	0.32 × 0.29 × 0.09 mm

Data collection top

Bruker APEXII CCD diffractometer	1662 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.106
Absorption correction: multi-scan (SADABS; Bruker, 2016)	θ_max = 25.0°, θ_min = 2.7°
T_min = 0.655, T_max = 0.746	h = −8→8
19764 measured reflections	k = −9→9
2241 independent reflections	l = −13→13

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.048	H-atom parameters constrained
wR(F²) = 0.107	w = 1/[σ²(F_o²) + (0.0235P)² + 1.1376P] where P = (F_o² + 2F_c²)/3
S = 1.09	(Δ/σ)_max < 0.001
2241 reflections	Δρ_max = 0.27 e Å⁻³
164 parameters	Δρ_min = −0.33 e Å⁻³
0 restraints

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	0.06076 (13)	0.17026 (12)	0.42861 (8)	0.0269 (3)
Cl2	−0.06759 (13)	0.53279 (13)	0.15245 (8)	0.0328 (3)
O1	0.1461 (3)	0.5253 (3)	0.37821 (19)	0.0191 (5)
O2	0.2783 (3)	0.3694 (3)	0.55085 (19)	0.0221 (6)
H2	0.157708	0.391949	0.574798	0.033*
C1	0.2966 (5)	0.3622 (4)	0.4322 (3)	0.0185 (8)
C11	0.2225 (5)	0.5758 (4)	0.2653 (3)	0.0192 (8)
C3	0.4551 (5)	0.0894 (4)	0.3551 (3)	0.0209 (8)
H3	0.474728	−0.022512	0.335419	0.025*
C10	0.1821 (5)	0.4890 (4)	0.1739 (3)	0.0194 (8)
C6	0.4571 (5)	0.4848 (4)	0.2673 (3)	0.0179 (7)
H6	0.518199	0.572267	0.266037	0.021*
C2	0.2846 (5)	0.1995 (4)	0.4009 (3)	0.0198 (8)
C9	0.3446 (5)	0.3828 (4)	0.1197 (3)	0.0211 (8)
H9	0.342144	0.317963	0.061141	0.025*
C4	0.6154 (5)	0.1623 (4)	0.3377 (3)	0.0203 (8)
H4	0.732882	0.086130	0.386498	0.024*
C7	0.5363 (5)	0.3772 (4)	0.1626 (3)	0.0206 (8)
H7	0.604311	0.435233	0.101481	0.025*
C8	0.6874 (5)	0.1927 (5)	0.2120 (3)	0.0240 (8)
H8A	0.688215	0.100747	0.168389	0.029*
H8B	0.826068	0.188696	0.207430	0.029*
C5	0.5042 (5)	0.3485 (4)	0.3779 (3)	0.0195 (8)
H5	0.584893	0.371253	0.431830	0.023*
C13	0.1802 (5)	0.8510 (5)	0.1251 (3)	0.0270 (9)
H13	0.152010	0.810452	0.061014	0.032*
C12	0.1281 (5)	0.7775 (4)	0.2438 (3)	0.0253 (8)
H12A	−0.021149	0.820022	0.254500	0.030*
H12B	0.174476	0.823785	0.301924	0.030*
C14	0.2611 (6)	0.9658 (5)	0.1035 (4)	0.0399 (11)
H14A	0.291514	1.009520	0.165285	0.048*
H14B	0.289666	1.006095	0.025767	0.048*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0202 (5)	0.0279 (5)	0.0360 (6)	−0.0142 (4)	−0.0005 (4)	−0.0023 (4)
Cl2	0.0145 (5)	0.0479 (6)	0.0353 (6)	−0.0122 (4)	−0.0051 (4)	−0.0026 (5)
O1	0.0093 (12)	0.0173 (12)	0.0240 (14)	0.0000 (10)	0.0021 (10)	−0.0013 (10)
O2	0.0154 (13)	0.0278 (14)	0.0207 (14)	−0.0065 (11)	0.0014 (10)	−0.0045 (11)
C1	0.0109 (17)	0.0171 (18)	0.023 (2)	−0.0020 (14)	0.0003 (14)	−0.0012 (15)
C11	0.0128 (18)	0.0183 (18)	0.022 (2)	−0.0031 (15)	0.0037 (14)	−0.0039 (15)
C3	0.0184 (19)	0.0157 (18)	0.027 (2)	−0.0049 (15)	−0.0040 (15)	−0.0026 (15)
C10	0.0112 (18)	0.0185 (18)	0.028 (2)	−0.0057 (15)	−0.0039 (15)	0.0008 (15)
C6	0.0095 (17)	0.0166 (18)	0.026 (2)	−0.0038 (14)	0.0024 (14)	−0.0049 (15)
C2	0.0189 (19)	0.0156 (18)	0.024 (2)	−0.0074 (16)	−0.0053 (15)	0.0039 (15)
C9	0.023 (2)	0.0166 (18)	0.022 (2)	−0.0073 (16)	−0.0035 (16)	−0.0008 (15)
C4	0.0108 (18)	0.0173 (18)	0.026 (2)	0.0015 (15)	−0.0040 (14)	−0.0026 (15)
C7	0.0134 (18)	0.0202 (18)	0.025 (2)	−0.0049 (15)	0.0038 (14)	−0.0021 (15)
C8	0.0125 (18)	0.024 (2)	0.030 (2)	−0.0022 (16)	−0.0001 (15)	−0.0045 (16)
C5	0.0116 (17)	0.0228 (19)	0.025 (2)	−0.0075 (15)	−0.0002 (14)	−0.0042 (15)
C13	0.026 (2)	0.0174 (19)	0.032 (2)	−0.0030 (16)	−0.0035 (16)	−0.0018 (16)
C12	0.019 (2)	0.0178 (19)	0.031 (2)	−0.0016 (16)	0.0050 (16)	−0.0032 (16)
C14	0.056 (3)	0.043 (3)	0.032 (2)	−0.033 (2)	−0.002 (2)	−0.0005 (19)

Geometric parameters (Å, º) top

Cl1—C2	1.731 (3)	C3—C4	1.506 (5)
Cl2—C10	1.734 (3)	C10—C9	1.315 (5)
O1—C1	1.444 (4)	C6—C7	1.557 (5)
O1—C11	1.445 (4)	C6—C5	1.545 (5)
O2—C1	1.394 (4)	C9—C7	1.515 (5)
C1—C2	1.506 (5)	C4—C8	1.526 (5)
C1—C5	1.536 (4)	C4—C5	1.552 (5)
C11—C10	1.508 (5)	C7—C8	1.534 (5)
C11—C6	1.550 (4)	C13—C12	1.501 (5)
C11—C12	1.520 (5)	C13—C14	1.300 (5)
C3—C2	1.316 (5)

C1—O1—C11	110.0 (2)	C5—C6—C11	105.6 (3)
O1—C1—C2	112.9 (3)	C5—C6—C7	106.9 (3)
O1—C1—C5	107.0 (3)	C1—C2—Cl1	119.8 (2)
O2—C1—O1	107.8 (3)	C3—C2—Cl1	126.3 (3)
O2—C1—C2	113.5 (3)	C3—C2—C1	113.9 (3)
O2—C1—C5	113.0 (3)	C10—C9—C7	111.3 (3)
C2—C1—C5	102.5 (3)	C3—C4—C8	114.6 (3)
O1—C11—C10	111.4 (3)	C3—C4—C5	103.4 (3)
O1—C11—C6	106.4 (2)	C8—C4—C5	106.3 (3)
O1—C11—C12	106.8 (3)	C9—C7—C6	103.2 (3)
C10—C11—C6	101.7 (3)	C9—C7—C8	115.4 (3)
C10—C11—C12	113.9 (3)	C8—C7—C6	105.4 (3)
C12—C11—C6	116.5 (3)	C4—C8—C7	105.9 (3)
C2—C3—C4	111.8 (3)	C1—C5—C6	105.2 (3)
C11—C10—Cl2	118.3 (2)	C1—C5—C4	107.3 (3)
C9—C10—Cl2	126.5 (3)	C6—C5—C4	106.6 (3)
C9—C10—C11	115.1 (3)	C14—C13—C12	125.0 (4)
C11—C6—C7	107.5 (3)	C13—C12—C11	113.3 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1ⁱ	0.84	2.06	2.893 (3)	173

Symmetry code: (i) −x, −y+1, −z+1.

Acknowledgements

We thank Darshan S. Mhatre for his help in collecting the X-ray data and with the structure refinement.

Funding information

Funding for this research was provided by: Defence Research and Development Organisation, Aeronautics Research and Development Board (grant No. ARDB/01/104189/M/I to Prof. S Kotha); University Grants Commission (scholarship to Saima Ansari); Council of Scientific and Industrial Research, India (scholarship to Naveen Kumar Gupta).

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