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The title bicyclic γ-lactone, C19H26O3, (II), the thermodynamically favored lactone, was formed in the reaction of (\pm)-cis-2,6,6-tri­methyl-trans-3-ethyl-4-oxo­cyclo­hexane­carboxyl­ic acid with p-methoxy­phenyl­magnesium bromide, following prolonged treatment under acidic conditions. The kinetically favored isomeric (\pm)-δ-lactone is described in the preceding paper [Xie et al. (2003). Acta Cryst. E59, o403–o405]. In lactone (II), basically composed of an aromatic ring appended to a [3.2.1] bicyclic system, the O—C(O)—C group is asymmetric, its O—C=O angle being 120.80 (15)° and its O=C—C angle being 130.46 (16)°.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803004288/om6134sup1.cif
Contains datablocks global, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803004288/om6134IIsup2.hkl
Contains datablock II

CCDC reference: 209914

Key indicators

  • Single-crystal X-ray study
  • T = 296 K
  • Mean [sigma](C-C) = 0.002 Å
  • R factor = 0.038
  • wR factor = 0.113
  • Data-to-parameter ratio = 14.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry








Comment top

We recently described the preparation, isolation and X-ray analysis of bicyclic δ-lactone (I) (Xie et al., 2003), which is the kinetically favored lactone formed in the reaction of (±)-cis-2,6,6-trimethyl-trans-3-ethyl-4-oxocyclohexanecarboxylic acid with p-methoxyphenylmagnesium bromide, followed by acidification with excess 3 N HCl, and the mixture worked up within an hour. When the acidified mixture was worked up after several days, the thermodynamically favored isomeric bicyclic γ-lactone, namely (±)-5-ethyl-endo-4-(4-methoxyphenyl)-2,2,anti-8-trimethyl-6- oxabicyclo[3.2.1]octan-7-one, (II), was obtained as the major product. This reaction is described in detail in the preceding paper (Xie et al., 2003).

The structure and atom numbering of (II) are shown in Fig. 1. Lactone (II) is basically composed of an aromatic ring appended to a [3.2.1] bicyclic system. The O—C(O)—C group is asymmetric, its O—CO angle being 120.80 (15)° and its OC—C angle being 130.46 (16)°. The four atoms comprising the lactone moiety, C1/C7/O6/C5, are essentially coplanar, as evidenced by the torsion angle, and the least-squares plane of this moiety is nearly perpendicular to the cyclohexane ring, the angle being 89.75 (8)°. Geometric values of interest are given in Table 1.

Experimental top

Compound (II) was prepared by the procedure described for (I) (Xie et al., 2003), except that the brown pasty solid obtained after the addition of 3 N HCl was left untouched for several days before being treated with p-TsOH·H2O. The resulting solid product was purified by recrystallization (ethyl acetate-hexane; m.p. 410.6–411.4 K) and shown to be (II). GC–MS: M+ 302, W·W. calculated: 302; NMR (CDCl3), 1H (300 MHz): δ 0.73 (t, J = 7.5 Hz, 3H), 1.02 (d, J = 6.9 Hz, 3H), 1.12 (s, 3H),1.18 (s, 3H), 1.53 (m, J = 7.2 Hz, 2H), 1.66 (d, J = 10.5 Hz, 1H), 1.67 (d, J = 7.5 Hz, 1H), 2.06 (s, 1H), 2.44 (q, J = 6.9 Hz, 1H), 2.92 (dd, J = 7.8 Hz, 10.5 Hz, 1H), 3.79 (s, 3H), 6.83 (d, J = 9.0 Hz, 2H), 7.24 (d, J = 9.0 Hz, 2H); 13C (75 MHz): δ 6.72, 14.30, 23.68, 25.99, 28.30, 31.80, 39.49, 44.49, 44.95, 55.16, 59.84, 91.52, 113.69, 129.66, 133.67 (2 C), 158.33 (2 C), 177.72.

Refinement top

The rotational orientations of the methyl H atoms were refined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997). All H atoms were refined as riding, with C—H distances ranging from 0.93 to 0.98 Å.

Computing details top

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Burla et al., 1989); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: TEXSAN, SHELXL97 and PLATON (Spek, 2000).

Figures top
[Figure 1] Fig. 1. The molecular structure and atom-numbering scheme for (II), with displacement ellipsoids at the 30% probability level.
(±)-5-Ethyl-endo-4-(4-methoxyphenyl)-2,2,anti-8-trimethyl-6- oxabicyclo[3.2.1]octan-7-one top
Crystal data top
C19H26O3F(000) = 656
Mr = 302.40Dx = 1.194 Mg m3
Monoclinic, P21/cMelting point = 410.6–411.4 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71069 Å
a = 18.318 (2) ÅCell parameters from 25 reflections
b = 7.597 (3) Åθ = 19.6–21.3°
c = 12.0935 (13) ŵ = 0.08 mm1
β = 91.86 (1)°T = 296 K
V = 1682.2 (7) Å3Prism, colorless
Z = 40.48 × 0.46 × 0.27 mm
Data collection top
Rigaku AFC-5S
diffractometer
Rint = 0.008
Radiation source: fine-focus sealed tubeθmax = 25.1°, θmin = 2.2°
Graphite monochromatorh = 021
ω scansk = 09
3069 measured reflectionsl = 1414
2971 independent reflections3 standard reflections every 100 reflections
2145 reflections with I > 2σ(I) intensity decay: 1.6%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.113H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0574P)2 + 0.3918P]
where P = (Fo2 + 2Fc2)/3
2971 reflections(Δ/σ)max < 0.001
204 parametersΔρmax = 0.14 e Å3
0 restraintsΔρmin = 0.19 e Å3
Crystal data top
C19H26O3V = 1682.2 (7) Å3
Mr = 302.40Z = 4
Monoclinic, P21/cMo Kα radiation
a = 18.318 (2) ŵ = 0.08 mm1
b = 7.597 (3) ÅT = 296 K
c = 12.0935 (13) Å0.48 × 0.46 × 0.27 mm
β = 91.86 (1)°
Data collection top
Rigaku AFC-5S
diffractometer
Rint = 0.008
3069 measured reflections3 standard reflections every 100 reflections
2971 independent reflections intensity decay: 1.6%
2145 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0380 restraints
wR(F2) = 0.113H-atom parameters constrained
S = 1.01Δρmax = 0.14 e Å3
2971 reflectionsΔρmin = 0.19 e Å3
204 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.93628 (7)0.3563 (2)0.63097 (11)0.0632 (4)
O20.53075 (6)0.60610 (17)0.89125 (10)0.0534 (3)
O60.81709 (6)0.38375 (14)0.59134 (9)0.0392 (3)
C10.89193 (9)0.5729 (2)0.49339 (13)0.0396 (4)
C20.88546 (9)0.7544 (2)0.55194 (14)0.0442 (4)
C30.81738 (9)0.7504 (2)0.62315 (14)0.0429 (4)
C40.74931 (8)0.6614 (2)0.56946 (13)0.0367 (4)
C50.77099 (8)0.4869 (2)0.51302 (12)0.0360 (4)
C70.88847 (9)0.4283 (2)0.57833 (14)0.0420 (4)
C80.82449 (9)0.5286 (2)0.42097 (13)0.0385 (4)
C90.95324 (10)0.7874 (3)0.62595 (18)0.0647 (6)
C100.87955 (12)0.9020 (2)0.46579 (18)0.0618 (5)
C110.70693 (9)0.3694 (2)0.48118 (15)0.0457 (4)
C120.65405 (11)0.4516 (3)0.39665 (17)0.0639 (6)
C130.83925 (11)0.3767 (2)0.34180 (15)0.0531 (5)
C140.68951 (8)0.6455 (2)0.65255 (13)0.0371 (4)
C150.69860 (9)0.5449 (2)0.74874 (14)0.0438 (4)
C160.64470 (9)0.5352 (2)0.82512 (14)0.0441 (4)
C170.57972 (9)0.6252 (2)0.80858 (13)0.0395 (4)
C180.56888 (9)0.7245 (2)0.71410 (14)0.0444 (4)
C190.62381 (9)0.7334 (2)0.63789 (14)0.0432 (4)
C200.46665 (11)0.7094 (3)0.88672 (19)0.0685 (6)
H10.93670.56530.45140.048*
H3a0.80480.87050.64190.051*
H3b0.82980.68960.69170.051*
H40.73100.74020.51080.044*
H80.80810.63270.37930.046*
H9a0.99570.79040.58150.097*
H9b0.95830.69460.67950.097*
H9c0.94830.89810.66330.097*
H10a0.83310.89480.42690.093*
H10b0.91800.88970.41420.093*
H10c0.88381.01390.50220.093*
H11a0.68070.34090.54720.055*
H11b0.72540.26020.45130.055*
H12a0.63190.55370.42820.096*
H12b0.61690.36770.37600.096*
H12c0.68000.48550.33230.096*
H13a0.87900.40750.29560.080*
H13b0.79630.35430.29640.080*
H13c0.85180.27300.38360.080*
H150.74190.48330.76140.053*
H160.65210.46740.88850.053*
H180.52520.78490.70150.053*
H190.61610.80120.57450.052*
H20a0.47960.83160.88300.103*
H20b0.43930.68870.95180.103*
H20c0.43750.67800.82230.103*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0442 (7)0.0797 (10)0.0655 (8)0.0093 (7)0.0023 (6)0.0243 (8)
O20.0429 (7)0.0645 (8)0.0537 (7)0.0063 (6)0.0142 (6)0.0048 (6)
O60.0373 (6)0.0401 (6)0.0403 (6)0.0004 (5)0.0023 (5)0.0101 (5)
C10.0382 (9)0.0418 (9)0.0393 (8)0.0025 (7)0.0085 (7)0.0018 (7)
C20.0416 (9)0.0449 (10)0.0464 (9)0.0106 (7)0.0052 (7)0.0039 (8)
C30.0425 (9)0.0420 (9)0.0443 (9)0.0051 (7)0.0036 (7)0.0075 (7)
C40.0374 (8)0.0356 (9)0.0371 (8)0.0002 (7)0.0010 (7)0.0025 (7)
C50.0387 (8)0.0333 (8)0.0359 (8)0.0022 (7)0.0022 (7)0.0047 (7)
C70.0389 (9)0.0467 (10)0.0407 (9)0.0004 (8)0.0034 (7)0.0030 (8)
C80.0479 (9)0.0329 (8)0.0349 (8)0.0002 (7)0.0026 (7)0.0025 (7)
C90.0440 (11)0.0780 (14)0.0720 (13)0.0166 (10)0.0013 (9)0.0165 (11)
C100.0754 (14)0.0426 (11)0.0683 (13)0.0161 (10)0.0129 (11)0.0041 (9)
C110.0458 (10)0.0404 (9)0.0507 (10)0.0084 (8)0.0043 (8)0.0009 (8)
C120.0617 (12)0.0611 (13)0.0675 (13)0.0088 (10)0.0210 (10)0.0027 (10)
C130.0697 (13)0.0463 (10)0.0438 (10)0.0014 (9)0.0074 (9)0.0042 (8)
C140.0360 (8)0.0380 (9)0.0372 (8)0.0005 (7)0.0006 (7)0.0007 (7)
C150.0375 (9)0.0481 (10)0.0459 (9)0.0100 (7)0.0011 (7)0.0062 (8)
C160.0459 (10)0.0439 (10)0.0426 (9)0.0066 (8)0.0035 (8)0.0092 (8)
C170.0358 (9)0.0406 (9)0.0423 (9)0.0008 (7)0.0049 (7)0.0017 (7)
C180.0348 (9)0.0493 (10)0.0491 (9)0.0078 (7)0.0014 (7)0.0013 (8)
C190.0415 (9)0.0459 (10)0.0420 (9)0.0045 (8)0.0025 (7)0.0069 (8)
C200.0459 (11)0.0875 (16)0.0731 (13)0.0171 (11)0.0182 (10)0.0035 (12)
Geometric parameters (Å, º) top
C1—C71.507 (2)C3—H3a0.9700
O6—C71.3646 (19)C3—H3b0.9700
O6—C51.4741 (18)C4—H40.9800
O1—C71.198 (2)C8—H80.9800
O2—C171.3724 (19)C9—H9a0.9600
O2—C201.412 (2)C9—H9b0.9600
C1—C81.529 (2)C9—H9c0.9600
C1—C21.556 (2)C10—H10a0.9600
C2—C91.528 (2)C10—H10b0.9600
C2—C101.532 (3)C10—H10c0.9600
C2—C31.539 (2)C11—H11a0.9700
C3—C41.543 (2)C11—H11b0.9700
C4—C141.515 (2)C12—H12a0.9600
C4—C51.549 (2)C12—H12b0.9600
C5—C111.514 (2)C12—H12c0.9600
C5—C81.540 (2)C13—H13a0.9600
C8—C131.529 (2)C13—H13b0.9600
C11—C121.520 (3)C13—H13c0.9600
C14—C191.383 (2)C15—H150.9300
C14—C151.397 (2)C16—H160.9300
C15—C161.376 (2)C18—H180.9300
C16—C171.382 (2)C19—H190.9300
C17—C181.378 (2)C20—H20a0.9600
C18—C191.388 (2)C20—H20b0.9600
C1—H10.9800C20—H20c0.9600
O1—C7—C1130.46 (16)C5—C4—H4106.9
C1—C7—O6108.74 (14)C13—C8—H8110.2
C5—O6—C7108.97 (11)C1—C8—H8110.2
C17—O2—C20118.39 (14)C5—C8—H8110.2
C7—C1—C8100.30 (13)C2—C9—H9a109.5
C7—C1—C2109.29 (13)C2—C9—H9b109.5
C8—C1—C2112.57 (14)H9a—C9—H9b109.5
C9—C2—C10108.45 (16)C2—C9—H9c109.5
C9—C2—C3109.48 (14)H9a—C9—H9c109.5
C10—C2—C3110.76 (15)H9b—C9—H9c109.5
C9—C2—C1109.85 (15)C2—C10—H10a109.5
C10—C2—C1110.11 (14)C2—C10—H10b109.5
C3—C2—C1108.19 (13)H10a—C10—H10b109.5
C2—C3—C4115.57 (13)C2—C10—H10c109.5
C14—C4—C3110.34 (13)H10a—C10—H10c109.5
C14—C4—C5115.17 (13)H10b—C10—H10c109.5
C3—C4—C5110.21 (13)H11a—C11—H11b107.7
O6—C5—C11105.83 (12)C5—C11—H11a108.8
O6—C5—C8102.06 (11)C12—C11—H11a108.8
C11—C5—C8116.32 (13)C5—C11—H11b108.8
O6—C5—C4108.76 (12)C12—C11—H11b108.8
C11—C5—C4114.16 (14)C11—C12—H12a109.5
C8—C5—C4108.73 (12)C11—C12—H12b109.5
O1—C7—O6120.80 (15)H12a—C12—H12b109.5
C13—C8—C1111.65 (14)C11—C12—H12c109.5
C13—C8—C5115.31 (14)H12a—C12—H12c109.5
C1—C8—C598.78 (12)H12b—C12—H12c109.5
C5—C11—C12113.60 (15)C8—C13—H13a109.5
C19—C14—C15116.79 (15)C8—C13—H13b109.5
C19—C14—C4121.43 (14)H13a—C13—H13b109.5
C15—C14—C4121.77 (14)C8—C13—H13c109.5
C16—C15—C14121.30 (15)H13a—C13—H13c109.5
C15—C16—C17120.66 (15)H13b—C13—H13c109.5
O2—C17—C18125.58 (15)C14—C19—H19118.7
O2—C17—C16115.00 (14)C18—C19—H19118.7
C18—C17—C16119.42 (15)O2—C20—H20a109.5
C17—C18—C19119.29 (15)O2—C20—H20b109.5
C14—C19—C18122.54 (15)H20a—C20—H20b109.5
C7—C1—H1111.4O2—C20—H20c109.5
C8—C1—H1111.4H20a—C20—H20c109.5
C2—C1—H1111.4H20b—C20—H20c109.5
C2—C3—H3a108.4C16—C15—H15119.3
C4—C3—H3a108.4C14—C15—H15119.3
C2—C3—H3b108.4C15—C16—H16119.7
C4—C3—H3b108.4C17—C16—H16119.7
H3a—C3—H3b107.4C17—C18—H18120.4
C14—C4—H4106.9C19—C18—H18120.4
C3—C4—H4106.9
C1—C7—O6—C53.11 (17)C7—C1—C8—C1378.85 (16)
C3—C4—C14—C19115.85 (17)C2—C1—C8—C13165.11 (13)
C3—C4—C14—C1562.6 (2)C7—C1—C8—C542.94 (14)
C7—C1—C2—C967.45 (18)C2—C1—C8—C573.10 (15)
C8—C1—C2—C9177.97 (14)O6—C5—C8—C1377.10 (16)
C7—C1—C2—C10173.18 (15)C11—C5—C8—C1337.5 (2)
C8—C1—C2—C1062.66 (18)C4—C5—C8—C13168.08 (14)
C7—C1—C2—C352.01 (17)O6—C5—C8—C141.99 (14)
C8—C1—C2—C358.51 (17)C11—C5—C8—C1156.63 (14)
C9—C2—C3—C4161.17 (16)C4—C5—C8—C172.83 (14)
C10—C2—C3—C479.29 (18)O6—C5—C11—C12177.93 (15)
C1—C2—C3—C441.48 (19)C8—C5—C11—C1265.4 (2)
C2—C3—C4—C14172.88 (14)C4—C5—C11—C1262.49 (19)
C2—C3—C4—C544.59 (19)C5—C4—C14—C19118.61 (17)
C7—O6—C5—C11147.30 (13)C5—C4—C14—C1562.9 (2)
C7—O6—C5—C825.17 (15)C19—C14—C15—C160.3 (2)
C7—O6—C5—C489.63 (15)C4—C14—C15—C16178.20 (15)
C14—C4—C5—O676.93 (15)C14—C15—C16—C170.0 (3)
C3—C4—C5—O648.68 (16)C20—O2—C17—C186.9 (3)
C14—C4—C5—C1140.99 (18)C20—O2—C17—C16172.94 (17)
C3—C4—C5—C11166.60 (13)C15—C16—C17—O2179.41 (15)
C14—C4—C5—C8172.69 (12)C15—C16—C17—C180.5 (3)
C3—C4—C5—C861.70 (16)O2—C17—C18—C19179.23 (16)
C5—O6—C7—O1177.40 (16)C16—C17—C18—C190.6 (3)
C8—C1—C7—O1150.4 (2)C15—C14—C19—C180.2 (2)
C2—C1—C7—O191.1 (2)C4—C14—C19—C18178.38 (15)
C8—C1—C7—O630.16 (16)C17—C18—C19—C140.3 (3)
C2—C1—C7—O688.32 (16)

Experimental details

Crystal data
Chemical formulaC19H26O3
Mr302.40
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)18.318 (2), 7.597 (3), 12.0935 (13)
β (°) 91.86 (1)
V3)1682.2 (7)
Z4
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.48 × 0.46 × 0.27
Data collection
DiffractometerRigaku AFC-5S
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3069, 2971, 2145
Rint0.008
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.113, 1.01
No. of reflections2971
No. of parameters204
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.14, 0.19

Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996), MSC/AFC Diffractometer Control Software, PROCESS in TEXSAN (Molecular Structure Corporation, 1997), SIR92 (Burla et al., 1989), LS in TEXSAN and SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), TEXSAN, SHELXL97 and PLATON (Spek, 2000).

Selected bond and torsion angles (º) top
O1—C7—C1130.46 (16)C5—O6—C7108.97 (11)
C1—C7—O6108.74 (14)
C1—C7—O6—C53.11 (17)C3—C4—C14—C1562.6 (2)
C3—C4—C14—C19115.85 (17)
 

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