organic compounds
(3S*,4S*,E)-tert-Butyl 3,4-dibromo-5-oxocyclooct-1-enecarboxylate
aDepartamento de Quimica Organica, Universidad de Salamanca, Plaza de los Caidos, 37008 Salamanca, Spain, and bServicio General de Rayos X, Universidad de Salamanca, Plaza de los Caidos, 37008 Salamanca, Spain
*Correspondence e-mail: nmg@usal.es
The title compound, C13H18Br2O3, was prepared by a bromination reaction of (1E,3Z)-methyl 5-oxocycloocta-1,3-dienecarboxylate, which was obtained by an epoxydation reaction of tert-butyl cyclooct-1,3-dienecarboxylate. The confirms unequivocally the of both chiral centres to be S. In the crystal, C—H⋯O interactions link the molecules into chains running along the c axis.
Related literature
For the Michael addition of enantiomerically pure lithium et al. (2005). For their importance in pharmacology, see: Fülöp et al. (2001). For the reactivity of the cycloocta-1,5-diene in basic medium, see: Huber et al. (1969, 1970). For the preparation of analogous unsaturated cyclooctane see: Garrido et al. (2008).
see: DaviesExperimental
Crystal data
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Data collection: APEX2 (Bruker 2006); cell SAINT (Bruker 2006); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Supporting information
10.1107/S1600536811053852/bt5753sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811053852/bt5753Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536811053852/bt5753Isup3.cml
Epoxydation reaction, synthesis of (1E,3Z)-tert-butyl 5-oxocycloocta-1,3-dienecarboxylate 4. Compound 1 (623.8 mg, 3.0 mmol, 1 equiv) was dissolved in DCM (30 ml), and stirred at 0°C, MCPBA (568.5 mg, 3.3 mmol, 1.1 equiv) was added slowly and the solution was stirred for 5 h at room temperature. The reaction mixture was quenched with saturated Na2S2O3 (10 ml), extracted with DCM (3 x 80 ml), washed with H2O, saturated NaHCO3 and Na2S2O3. The combined organic extracts were dried over Na2SO4, filtered and concentrated in vacuo. Purification by silica gel for flash νmax (neat): 2976 and 2868 (C—H), 1707 (C=OOtBu), 1663 (C=O), 1456, 1370, 1292 (C—O), 1252, 1157 cm-1. 1H NMR (400 MHz; CDCl3): δ 1.52 (9H, s, COOC(CH3)3); 2.10 (2H, quint, J 6.6, H-7); 2.50 (2H, t, J 6.6, H-8); 2.57 (2H, t, J 6.6, H-6); 6.03 (1H, d, J 12.6, H-4); 6.57 (1H, dd, J 5.5 and 12.6, H-3); 7.26 (1H, d, J 5.5, H-2). 13C RMN (50 MHz; CDCl3): δ 26.3 (CH2, C-7); 28.0 (CH3 x 3, COOC(CH3)3); 31.8 (CH2, C-8); 38.5 (CH2, C-6); 81.4 (C, COOC(CH3)3); 133.6 (CH, C-4); 134.7 (CH, C-2); 135.8 (CH, C-3); 140.1 (C, C-1); 165.5 (C, COOC(CH3)3); 205.2 (C, C-5). m/z (Cl+) (rel. intensity): 222 (M+, 5) 205 (3), 186 (5), 166 (19), 149 (19), 121 (22), 94 (13), 77 (26), 57 (100).
(Hex/EtOAc (99:1 v/v) gave recovery of starting material (16%), (1Z,3R*,4S*) tert-butyl cycloocta-1,3-diene carboxylate 3,4 oxide 2 (450 mg, 67%), (1R*,2S*,3E) tert-butyl cycloocta-3,4-diene carboxylate 1,2 oxide 3 (47 mg, 7%), (1E,3Z)-tert-butyl 5-hydroxycycloocta-1,3-dienecarboxylate 5 (47 mg, 7%) and (1E,3Z)-tert-butyl 5-oxocycloocta-1,3-dienecarboxylate 4 as a pale yellow oil (27 mg, 4%), IRSynthesis of (3R*,4R*,E)-tert-butyl 3,4-dibromo-5-oxocycloocta-1-enecarboxylate 6. Compound 4 (27.00 mg, 0.12 mmol) was dissolved in CCl4 (10 ml) and the reaction system was stirred and cooled down at 0°C. After, Br2 (0.01 ml, 31 mmol) was added and stirred for 30 min, the ice bath was removed and stirred for 4 h at r.t. The reaction mixture was dissolved in DCM (20 ml), washed with HCl 2 N., NaHCO3(sat.), H2O and NaCl (sat.); dried over Na2SO4, filtered and concentrated in vacuo. It afforded tert-butyl 3,4-dibromo-5-oxocyclooct-1-enecarboxylate 6 (43.00 mg, 91%) which crystallizes in Hex/EtOAc (1:1 v/v), mp 161–162 °C, IR νmax (neat): 2976 and 2930 (C—H), 1712 (C=O), 1449 (C=C), 1369, 1292 (C—O), 1253, 1159, 1127, 1110 (C—Br) cm-1. 1H NMR (400 MHz; CDCl3): δ 1.47 (9H, s, COOC(CH3)3); 2.00–3.02 (6H, m, H-6, H-7, H-8); 4.23 (1H, d, J 11.2, H-4); 5.01 (1H, dd, J 11.2 and 9.6, H-3); 6.80 (1H, d, J 9.6, H-2). 13C RMN (50 MHz; CDCl3): δ 27.1 (CH2, C-7); 27.8 (CH2, C-8); 28.2 (CH3 x 3, COOC(CH3)3); 37.8 (CH2, C-6); 46.8 (CH); 60.4 (CH); 82.2 (C,COOC(CH3)3); 137.5 (CH, C-2); 138.1 (C, C-1); 164.7 (C, COOC(CH3)3); 202.0 (C, C-5). HRMS (ESI) m/z calcd.for C13H18Br2O3 [M+Na]:402.9515; found 402.9543; R—X.
The hydrogen atoms were positioned geometrically, with C—H distances constrained to 0.93 Å (aromatic CH), 0.96 Å (methyl CH3), 0.97 Å methylene CH2), 098 Å (methine CH) and refined in riding mode with Uiso(H) = xUeq(C), where x = 1.5 for methyl H atoms and x = 1.2 for all other atoms.
Data collection: APEX2 (Bruker 2006); cell
SAINT (Bruker 2006); data reduction: SAINT (Bruker 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C13H18Br2O3 | F(000) = 760 |
Mr = 382.09 | Dx = 1.669 Mg m−3 |
Orthorhombic, Pca21 | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: P 2c -2ac | Cell parameters from 9578 reflections |
a = 14.0658 (4) Å | θ = 4.6–66.5° |
b = 9.5990 (3) Å | µ = 6.76 mm−1 |
c = 11.2657 (3) Å | T = 298 K |
V = 1521.07 (8) Å3 | Prismatic, colourless |
Z = 4 | 0.24 × 0.14 × 0.10 mm |
Bruker APEXII CCD area-detector diffractometer | 2170 independent reflections |
Radiation source: fine-focus sealed tube | 2153 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.048 |
phi and ω scans | θmax = 66.5°, θmin = 4.6° |
Absorption correction: multi-scan (SADABS; Bruker, 2006) | h = −16→16 |
Tmin = 0.370, Tmax = 0.509 | k = −11→11 |
10215 measured reflections | l = −10→13 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.029 | H-atom parameters constrained |
wR(F2) = 0.075 | w = 1/[σ2(Fo2) + (0.0448P)2 + 0.2923P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max = 0.001 |
2170 reflections | Δρmax = 0.32 e Å−3 |
166 parameters | Δρmin = −0.46 e Å−3 |
1 restraint | Absolute structure: Flack (1983), 803 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.06 (3) |
C13H18Br2O3 | V = 1521.07 (8) Å3 |
Mr = 382.09 | Z = 4 |
Orthorhombic, Pca21 | Cu Kα radiation |
a = 14.0658 (4) Å | µ = 6.76 mm−1 |
b = 9.5990 (3) Å | T = 298 K |
c = 11.2657 (3) Å | 0.24 × 0.14 × 0.10 mm |
Bruker APEXII CCD area-detector diffractometer | 2170 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2006) | 2153 reflections with I > 2σ(I) |
Tmin = 0.370, Tmax = 0.509 | Rint = 0.048 |
10215 measured reflections |
R[F2 > 2σ(F2)] = 0.029 | H-atom parameters constrained |
wR(F2) = 0.075 | Δρmax = 0.32 e Å−3 |
S = 1.09 | Δρmin = −0.46 e Å−3 |
2170 reflections | Absolute structure: Flack (1983), 803 Friedel pairs |
166 parameters | Absolute structure parameter: 0.06 (3) |
1 restraint |
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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.76354 (2) | 0.96781 (4) | 0.67951 (5) | 0.04630 (14) | |
Br2 | 0.94176 (3) | 0.72748 (4) | 0.77399 (5) | 0.05922 (16) | |
O1 | 0.9457 (2) | 1.4186 (4) | 1.0183 (4) | 0.0671 (10) | |
O2 | 0.79492 (19) | 1.3427 (3) | 0.9957 (3) | 0.0429 (6) | |
O3 | 0.9590 (2) | 0.9175 (4) | 1.0552 (3) | 0.0605 (8) | |
C1 | 0.9148 (3) | 1.2311 (3) | 0.8856 (4) | 0.0368 (7) | |
C2 | 0.8510 (2) | 1.1346 (3) | 0.8551 (3) | 0.0359 (7) | |
H2 | 0.7890 | 1.1450 | 0.8824 | 0.043* | |
C3 | 0.8733 (2) | 1.0108 (3) | 0.7796 (4) | 0.0350 (7) | |
H3 | 0.9285 | 1.0313 | 0.7294 | 0.042* | |
C4 | 0.8964 (3) | 0.8890 (4) | 0.8617 (3) | 0.0403 (7) | |
H4 | 0.8391 | 0.8632 | 0.9060 | 0.048* | |
C5 | 0.9749 (3) | 0.9286 (4) | 0.9494 (4) | 0.0403 (8) | |
C6 | 1.0669 (3) | 0.9841 (5) | 0.9021 (4) | 0.0481 (10) | |
H6B | 1.0700 | 0.9652 | 0.8176 | 0.058* | |
H6A | 1.1189 | 0.9347 | 0.9398 | 0.058* | |
C7 | 1.0806 (3) | 1.1419 (5) | 0.9221 (5) | 0.0503 (10) | |
H7B | 1.0685 | 1.1627 | 1.0050 | 0.060* | |
H7A | 1.1463 | 1.1655 | 0.9057 | 0.060* | |
C8 | 1.0164 (3) | 1.2335 (4) | 0.8455 (4) | 0.0455 (9) | |
H8B | 1.0396 | 1.3286 | 0.8479 | 0.055* | |
H8A | 1.0197 | 1.2018 | 0.7638 | 0.055* | |
C9 | 0.8876 (3) | 1.3426 (3) | 0.9735 (3) | 0.0407 (8) | |
C10 | 0.7509 (3) | 1.4418 (4) | 1.0807 (5) | 0.0488 (10) | |
C11 | 0.7934 (4) | 1.4216 (6) | 1.2022 (4) | 0.0701 (13) | |
H11A | 0.7917 | 1.3246 | 1.2227 | 0.105* | |
H11B | 0.7576 | 1.4740 | 1.2594 | 0.105* | |
H11C | 0.8581 | 1.4534 | 1.2020 | 0.105* | |
C12 | 0.7647 (6) | 1.5884 (5) | 1.0332 (7) | 0.086 (2) | |
H12A | 0.8314 | 1.6092 | 1.0295 | 0.130* | |
H12B | 0.7338 | 1.6537 | 1.0849 | 0.130* | |
H12C | 0.7377 | 1.5950 | 0.9552 | 0.130* | |
C13 | 0.6482 (4) | 1.3957 (6) | 1.0791 (6) | 0.0723 (14) | |
H13A | 0.6223 | 1.4091 | 1.0011 | 0.108* | |
H13B | 0.6125 | 1.4497 | 1.1353 | 0.108* | |
H13C | 0.6444 | 1.2988 | 1.1000 | 0.108* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.0408 (2) | 0.0566 (2) | 0.0415 (2) | −0.00053 (14) | −0.0054 (2) | −0.01174 (18) |
Br2 | 0.0757 (3) | 0.0393 (2) | 0.0626 (3) | 0.01023 (16) | −0.0059 (2) | −0.0133 (2) |
O1 | 0.0599 (18) | 0.0619 (19) | 0.079 (3) | −0.0142 (15) | 0.0064 (16) | −0.0333 (17) |
O2 | 0.0436 (13) | 0.0401 (12) | 0.0451 (15) | 0.0075 (11) | 0.0017 (12) | −0.0121 (11) |
O3 | 0.0719 (19) | 0.0752 (19) | 0.0343 (17) | −0.0037 (15) | −0.0071 (14) | 0.0051 (16) |
C1 | 0.0403 (17) | 0.0328 (15) | 0.0374 (19) | 0.0002 (13) | 0.0039 (17) | −0.0032 (14) |
C2 | 0.0355 (16) | 0.0375 (15) | 0.0347 (18) | 0.0076 (13) | 0.0050 (14) | −0.0044 (14) |
C3 | 0.0347 (17) | 0.0374 (14) | 0.0330 (17) | −0.0026 (13) | 0.0021 (16) | −0.0025 (15) |
C4 | 0.0439 (18) | 0.0394 (15) | 0.038 (2) | −0.0016 (14) | 0.0021 (17) | −0.0007 (14) |
C5 | 0.0402 (19) | 0.0435 (16) | 0.037 (2) | 0.0070 (16) | −0.0026 (16) | −0.0026 (16) |
C6 | 0.0339 (19) | 0.057 (2) | 0.054 (3) | 0.0070 (16) | −0.0030 (17) | −0.0068 (19) |
C7 | 0.0347 (17) | 0.060 (2) | 0.056 (3) | −0.0034 (17) | 0.0025 (17) | −0.0164 (19) |
C8 | 0.044 (2) | 0.0453 (17) | 0.047 (2) | −0.0076 (15) | 0.0098 (17) | −0.0082 (15) |
C9 | 0.050 (2) | 0.0352 (15) | 0.037 (2) | 0.0011 (15) | 0.0018 (16) | −0.0017 (14) |
C10 | 0.066 (2) | 0.0397 (17) | 0.040 (2) | 0.0135 (17) | 0.009 (2) | −0.0088 (18) |
C11 | 0.088 (3) | 0.082 (3) | 0.041 (3) | −0.001 (3) | 0.006 (2) | −0.006 (2) |
C12 | 0.138 (5) | 0.038 (2) | 0.083 (4) | 0.026 (3) | 0.038 (4) | 0.002 (2) |
C13 | 0.063 (3) | 0.076 (3) | 0.078 (4) | 0.019 (2) | 0.005 (3) | −0.023 (3) |
Br1—C3 | 1.956 (4) | C6—H6A | 0.9700 |
Br2—C4 | 1.946 (4) | C7—C8 | 1.528 (7) |
O1—C9 | 1.206 (5) | C7—H7B | 0.9700 |
O2—C9 | 1.328 (5) | C7—H7A | 0.9700 |
O2—C10 | 1.486 (5) | C8—H8B | 0.9700 |
O3—C5 | 1.217 (5) | C8—H8A | 0.9700 |
C1—C2 | 1.334 (5) | C10—C11 | 1.507 (7) |
C1—C8 | 1.499 (5) | C10—C13 | 1.511 (7) |
C1—C9 | 1.508 (5) | C10—C12 | 1.518 (7) |
C2—C3 | 1.495 (5) | C11—H11A | 0.9600 |
C2—H2 | 0.9300 | C11—H11B | 0.9600 |
C3—C4 | 1.526 (5) | C11—H11C | 0.9600 |
C3—H3 | 0.9800 | C12—H12A | 0.9600 |
C4—C5 | 1.529 (6) | C12—H12B | 0.9600 |
C4—H4 | 0.9800 | C12—H12C | 0.9600 |
C5—C6 | 1.498 (6) | C13—H13A | 0.9600 |
C6—C7 | 1.543 (6) | C13—H13B | 0.9600 |
C6—H6B | 0.9700 | C13—H13C | 0.9600 |
C9—O2—C10 | 122.1 (3) | C1—C8—C7 | 112.6 (4) |
C2—C1—C8 | 125.0 (3) | C1—C8—H8B | 109.1 |
C2—C1—C9 | 119.5 (3) | C7—C8—H8B | 109.1 |
C8—C1—C9 | 115.4 (3) | C1—C8—H8A | 109.1 |
C1—C2—C3 | 123.9 (3) | C7—C8—H8A | 109.1 |
C1—C2—H2 | 118.1 | H8B—C8—H8A | 107.8 |
C3—C2—H2 | 118.1 | O1—C9—O2 | 125.9 (3) |
C2—C3—C4 | 108.0 (3) | O1—C9—C1 | 122.2 (3) |
C2—C3—Br1 | 109.3 (2) | O2—C9—C1 | 111.9 (3) |
C4—C3—Br1 | 110.8 (2) | O2—C10—C11 | 109.7 (4) |
C2—C3—H3 | 109.6 | O2—C10—C13 | 101.7 (4) |
C4—C3—H3 | 109.6 | C11—C10—C13 | 110.7 (5) |
Br1—C3—H3 | 109.6 | O2—C10—C12 | 108.3 (4) |
C3—C4—C5 | 110.8 (3) | C11—C10—C12 | 112.9 (5) |
C3—C4—Br2 | 111.9 (3) | C13—C10—C12 | 113.0 (5) |
C5—C4—Br2 | 106.8 (2) | C10—C11—H11A | 109.5 |
C3—C4—H4 | 109.1 | C10—C11—H11B | 109.5 |
C5—C4—H4 | 109.1 | H11A—C11—H11B | 109.5 |
Br2—C4—H4 | 109.1 | C10—C11—H11C | 109.5 |
O3—C5—C6 | 122.5 (4) | H11A—C11—H11C | 109.5 |
O3—C5—C4 | 118.6 (4) | H11B—C11—H11C | 109.5 |
C6—C5—C4 | 118.9 (3) | C10—C12—H12A | 109.5 |
C5—C6—C7 | 113.9 (3) | C10—C12—H12B | 109.5 |
C5—C6—H6B | 108.8 | H12A—C12—H12B | 109.5 |
C7—C6—H6B | 108.8 | C10—C12—H12C | 109.5 |
C5—C6—H6A | 108.8 | H12A—C12—H12C | 109.5 |
C7—C6—H6A | 108.8 | H12B—C12—H12C | 109.5 |
H6B—C6—H6A | 107.7 | C10—C13—H13A | 109.5 |
C8—C7—C6 | 114.1 (4) | C10—C13—H13B | 109.5 |
C8—C7—H7B | 108.7 | H13A—C13—H13B | 109.5 |
C6—C7—H7B | 108.7 | C10—C13—H13C | 109.5 |
C8—C7—H7A | 108.7 | H13A—C13—H13C | 109.5 |
C6—C7—H7A | 108.7 | H13B—C13—H13C | 109.5 |
H7B—C7—H7A | 107.6 |
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O3i | 0.98 | 2.57 | 3.525 (5) | 165 |
C8—H8A···O3i | 0.97 | 2.63 | 3.590 (6) | 172 |
Symmetry code: (i) −x+2, −y+2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C13H18Br2O3 |
Mr | 382.09 |
Crystal system, space group | Orthorhombic, Pca21 |
Temperature (K) | 298 |
a, b, c (Å) | 14.0658 (4), 9.5990 (3), 11.2657 (3) |
V (Å3) | 1521.07 (8) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 6.76 |
Crystal size (mm) | 0.24 × 0.14 × 0.10 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2006) |
Tmin, Tmax | 0.370, 0.509 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10215, 2170, 2153 |
Rint | 0.048 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.075, 1.09 |
No. of reflections | 2170 |
No. of parameters | 166 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.32, −0.46 |
Absolute structure | Flack (1983), 803 Friedel pairs |
Absolute structure parameter | 0.06 (3) |
Computer programs: APEX2 (Bruker 2006), SAINT (Bruker 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2006), SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O3i | 0.9800 | 2.5700 | 3.525 (5) | 165.00 |
C8—H8A···O3i | 0.97 | 2.63 | 3.590 (6) | 171.8 |
Symmetry code: (i) −x+2, −y+2, z−1/2. |
Acknowledgements
The authors are grateful to the FSE, the Spanish MICINN (EUI 2008–00173) and (CTQ 2009–11172/BQU) and the Junta de Castilla y Leon (Spain) for financial support (GR-178 and SA001A09). The authors also thank Grupo Santander for the doctoral fellowship awarded to MB.
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Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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In our research group there has been an enormous interest in the synthesis of conjugated unsaturated esters used as starting material in the Michael addition of enantiomerically pure lithium amides (Davies et al., 2005) as a base tool in the asymmetric synthesis of β-amino acids and alkaloids because of their interest and value in the development of biologically active compounds for the pharmacology industry (Fülöp et al., 2001). Considering that the reactivity of the cycloocta-1,5-diene is very peculiar, highlighting its trend in basic medium to conjugate its double bonds (Huber et al., 1969) because of the greater thermodynamic stability (Huber et al., 1970), is necessary and important to establish the exact structure in this class of unsaturated rings. This conjugation was determined previously for an isomer of compound 1 (tert-butyl cyclooct-1,7-dienecarboxylate) (Garrido et al., 2008) and herein for compound 1 (tert-butylcyclooct-1,3-dienecarboxylate) by R—X spectroscopy of compound 6 which confirms unequivocally its configuration and structure. The crystal was afforded by epoxydation reaction of compound 1 with MCPBA and bromination reaction of compound 4 (Fig. 1).
The crystal contains an unique molecule in the asymmetric unit. The title molecule consists of a ring cyclooctene with two bromine atoms, a carbonyl group and a tert-butoxycarbonyl group as susbtituents. All the bond lengths and angles are within the normal ranges. The Br1—C3 and Br2—C4 bond lengths are 1.956 (4) Å and 1.946 (4) Å, respectively. The bromine atoms at C3 and C4 are nearly coplanar with the cycloctene ring being the Br1—C3—C4—C5 and Br2—C4—C3—C2 torsion angles of 173.6 (3)° and -173.0 (1)°, respectively. In the case of the tert-butoxycarbonyl group at C1 is also coplanar with the cycloctene ring being the O2—C9—O1—C1 torsion angle of 178.2 (7)°. The carbonyl group at atom C5 is twisted with the cycloctene ring being the O3—C5—C4—C3 torsion angle of 123.3 (8)°.
In the crystal structure, molecules are connected by intermolecular C—H···O interactions to form infinite chains running along [001] direction, which seems to be effective in the stabilization of the structure (Table 1).