organic compounds
(2aR*,5S*,6aS*,8aS*,E)-Ethyl 5-hydroxy-7,7,8a-trimethyl-8-oxo-2,2a,6,6a,7,8,8a,8b-octahydro-1H-pentaleno[1,6-bc]oxepine-4-carboxylate
aDepartment of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India
*Correspondence e-mail: gmsc@uohyd.ernet.in, gm@orgchem.iisc.ernet.in
The title compound, C17H24O5, featuring a 2-carbethoxy-3-oxepanone unit in its intramolecularly O—H⋯O hydrogen-bonded enol form, was obtained via [(CF3CO2)2Rh]2-catalysed intramolecular O—H bond insertion in the α-diazo-ω-hydroxy-β-ketoester, ethyl 4-[(1S,3aS,6R,6aS)-6-hydroxy-2,2,3a-trimethyl-3-oxo-octahydropentalen-1-yl]-2-diazo-3-oxobutanoate. The seven-membered oxacyclic ring, thus constructed on a cis-fused diquinane platform, was found to adopt a distorted boat–sofa conformation.
Related literature
For rhodium carbenoid-mediated intermolecular O—H insertion reactions and their application to natural product synthesis, see: Paulissen et al. (1973); Cox et al. (1994); Haigh (1994); Aller et al. (1995); Shi et al. (1995); Bulugahapitiya et al. (1997); Moody & Miller (1998); Nelson et al. (2000); Medeiros & Wood (2010); Freeman et al. (2010); Morton et al. (2012). For rhodium-catalysed intramolecular O—H insertion reactions, see: Paulissen et al. (1974); Moyer et al. (1985); Moody & Taylor (1987); Heslin & Moody (1988); Davies et al. (1990); Moody et al. (1992); Sarabia-Garciá et al. (1994); Padwa & Sá (1999); Im et al. (2005). For reviews on rhodium-mediated C—H insertion reactions, see: Doyle et al. (2010); Davies & Morton (2011). For the construction of an angularly fused triquinane skeleton via RhII-catalysed intramolecular C—H insertion, see: Srikrishna et al. (2012). For the isolation and synthesis of penifulvin A, see: Shim et al. (2006); Gaich & Mulzer (2009); Mehta & Khan (2012). For the application of p-acetamidobenzenesulfonyl azide as a diazo transfer reagent, see: Baum et al. (1987). For ring conformations, see: Cremer & Pople (1975); Boessenkool & Boeyens (1980).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2007); cell SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009).
Supporting information
10.1107/S1600536812046776/ds2220sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812046776/ds2220Isup2.hkl
As shown in Figure 1, the title compound 1 was prepared from the the β-ketoester 3 via the intermediate diazoester 2. Thus, 3, upon treatment with p-acetamidobenzenesulfonyl azide and triethylamine, afforded 2. The α-diazo-ω-hydroxy-β-ketoester 2 underwent smooth in presence of catalytic rhodium(II) trifluoroacetate dimer to deliver the oxepanone 1, which crystallized as thin colorless plates from 1:1 dichloromethane-hexanes.
The methine (CH) and methylene (CH2) H atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms with C—H distances 0.93 and 0.97 Å respectively, and Uiso(H) = 1.2Ueq(C). The methyl (CH3) hydrogen atoms were constrained to an ideal geometry with C—H distances as 0.96 Å and Uiso(H) = 1.5Ueq(C). During
each methyl group was however allowed to rotate freely about its C—C bond. The position of the hydroxyl hydrogen atom was refined freely, along with an isotropic displacement parameter.Data collection: APEX2 (Bruker, 2007); cell
SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009).C17H24O5 | F(000) = 1328 |
Mr = 308.36 | Dx = 1.209 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 939 reflections |
a = 8.447 (5) Å | θ = 2.8–19.5° |
b = 18.454 (14) Å | µ = 0.09 mm−1 |
c = 21.735 (15) Å | T = 291 K |
V = 3388 (4) Å3 | Plate, colorless |
Z = 8 | 0.20 × 0.18 × 0.08 mm |
Bruker APEXII CCD diffractometer | 3153 independent reflections |
Radiation source: fine-focus sealed tube | 1408 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.087 |
ϕ and ω scans | θmax = 25.5°, θmin = 1.9° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −10→7 |
Tmin = 0.983, Tmax = 0.993 | k = −22→18 |
14606 measured reflections | l = −26→26 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.053 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.149 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.89 | w = 1/[σ2(Fo2) + (0.0717P)2] where P = (Fo2 + 2Fc2)/3 |
3153 reflections | (Δ/σ)max < 0.001 |
207 parameters | Δρmax = 0.17 e Å−3 |
0 restraints | Δρmin = −0.17 e Å−3 |
C17H24O5 | V = 3388 (4) Å3 |
Mr = 308.36 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 8.447 (5) Å | µ = 0.09 mm−1 |
b = 18.454 (14) Å | T = 291 K |
c = 21.735 (15) Å | 0.20 × 0.18 × 0.08 mm |
Bruker APEXII CCD diffractometer | 3153 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1408 reflections with I > 2σ(I) |
Tmin = 0.983, Tmax = 0.993 | Rint = 0.087 |
14606 measured reflections |
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.149 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.89 | Δρmax = 0.17 e Å−3 |
3153 reflections | Δρmin = −0.17 e Å−3 |
207 parameters |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 | ||
O1 | 0.1027 (3) | 0.15812 (15) | 1.02261 (10) | 0.0990 (9) | |
O2 | 0.0947 (2) | 0.13477 (12) | 0.69261 (9) | 0.0655 (6) | |
H2O | 0.125 (4) | 0.0976 (18) | 0.6660 (15) | 0.090 (12)* | |
O3 | 0.1391 (2) | −0.00529 (10) | 0.80956 (7) | 0.0545 (5) | |
O4 | 0.1993 (2) | 0.01550 (12) | 0.64764 (8) | 0.0717 (6) | |
O5 | 0.2612 (2) | −0.07327 (12) | 0.71407 (8) | 0.0678 (6) | |
C1 | 0.0661 (3) | 0.12205 (14) | 0.86389 (11) | 0.0471 (7) | |
H1 | −0.0058 | 0.0810 | 0.8699 | 0.057* | |
C2 | 0.0332 (3) | 0.17697 (15) | 0.91600 (12) | 0.0544 (8) | |
C3 | 0.1256 (3) | 0.14428 (17) | 0.96932 (13) | 0.0623 (8) | |
C4 | 0.2513 (3) | 0.09177 (16) | 0.94596 (12) | 0.0568 (8) | |
C5 | 0.2035 (5) | 0.01234 (18) | 0.95976 (14) | 0.0888 (11) | |
H5A | 0.2518 | −0.0039 | 0.9978 | 0.107* | |
H5B | 0.0895 | 0.0083 | 0.9637 | 0.107* | |
C6 | 0.2602 (5) | −0.03189 (19) | 0.90749 (14) | 0.0906 (12) | |
H6A | 0.1898 | −0.0726 | 0.9006 | 0.109* | |
H6B | 0.3655 | −0.0504 | 0.9158 | 0.109* | |
C7 | 0.2627 (3) | 0.01697 (15) | 0.85202 (12) | 0.0575 (8) | |
H7 | 0.3661 | 0.0139 | 0.8317 | 0.069* | |
C8 | 0.2347 (3) | 0.09461 (14) | 0.87520 (11) | 0.0474 (7) | |
H8 | 0.3125 | 0.1280 | 0.8574 | 0.057* | |
C9 | 0.4153 (4) | 0.1103 (2) | 0.97087 (15) | 0.0970 (12) | |
H9A | 0.4449 | 0.1580 | 0.9573 | 0.145* | |
H9B | 0.4908 | 0.0757 | 0.9559 | 0.145* | |
H9C | 0.4133 | 0.1090 | 1.0150 | 0.145* | |
C10 | −0.1415 (4) | 0.1859 (2) | 0.93120 (14) | 0.0795 (11) | |
H10A | −0.1868 | 0.1394 | 0.9400 | 0.119* | |
H10B | −0.1952 | 0.2072 | 0.8967 | 0.119* | |
H10C | −0.1527 | 0.2168 | 0.9664 | 0.119* | |
C11 | 0.1093 (4) | 0.25222 (16) | 0.90386 (15) | 0.0781 (10) | |
H11A | 0.1031 | 0.2811 | 0.9405 | 0.117* | |
H11B | 0.0537 | 0.2761 | 0.8711 | 0.117* | |
H11C | 0.2183 | 0.2460 | 0.8925 | 0.117* | |
C12 | 0.0415 (3) | 0.14979 (16) | 0.79823 (11) | 0.0569 (8) | |
H12A | −0.0704 | 0.1595 | 0.7925 | 0.068* | |
H12B | 0.0971 | 0.1955 | 0.7940 | 0.068* | |
C13 | 0.0951 (3) | 0.10042 (16) | 0.74780 (12) | 0.0510 (7) | |
C14 | 0.1445 (3) | 0.03157 (16) | 0.75362 (11) | 0.0512 (7) | |
C15 | 0.2038 (3) | −0.00865 (17) | 0.70042 (13) | 0.0572 (8) | |
C16 | 0.3258 (4) | −0.11534 (19) | 0.66252 (15) | 0.0833 (11) | |
H16A | 0.2406 | −0.1329 | 0.6366 | 0.100* | |
H16B | 0.3950 | −0.0852 | 0.6378 | 0.100* | |
C17 | 0.4146 (6) | −0.1765 (2) | 0.68814 (18) | 0.1264 (17) | |
H17A | 0.4935 | −0.1587 | 0.7161 | 0.190* | |
H17B | 0.4650 | −0.2027 | 0.6554 | 0.190* | |
H17C | 0.3435 | −0.2081 | 0.7097 | 0.190* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.113 (2) | 0.137 (2) | 0.0465 (13) | 0.0369 (16) | −0.0008 (12) | −0.0152 (14) |
O2 | 0.0791 (15) | 0.0722 (16) | 0.0452 (12) | 0.0013 (12) | −0.0053 (10) | 0.0083 (12) |
O3 | 0.0605 (13) | 0.0555 (13) | 0.0474 (11) | −0.0043 (9) | 0.0016 (9) | −0.0012 (9) |
O4 | 0.0820 (16) | 0.0883 (16) | 0.0448 (12) | 0.0032 (12) | 0.0027 (10) | −0.0031 (11) |
O5 | 0.0850 (16) | 0.0645 (14) | 0.0540 (12) | 0.0051 (12) | 0.0061 (10) | −0.0092 (11) |
C1 | 0.0407 (18) | 0.0550 (17) | 0.0456 (16) | −0.0004 (13) | −0.0013 (12) | −0.0012 (13) |
C2 | 0.0495 (19) | 0.060 (2) | 0.0541 (17) | 0.0038 (15) | −0.0001 (13) | −0.0068 (15) |
C3 | 0.063 (2) | 0.078 (2) | 0.0463 (18) | −0.0012 (17) | −0.0008 (15) | −0.0052 (16) |
C4 | 0.054 (2) | 0.073 (2) | 0.0438 (15) | 0.0052 (16) | −0.0048 (13) | −0.0029 (15) |
C5 | 0.117 (3) | 0.085 (3) | 0.064 (2) | 0.019 (2) | 0.0199 (19) | 0.023 (2) |
C6 | 0.128 (3) | 0.076 (2) | 0.067 (2) | 0.010 (2) | −0.022 (2) | 0.013 (2) |
C7 | 0.058 (2) | 0.0618 (19) | 0.0524 (16) | 0.0087 (15) | −0.0061 (14) | −0.0047 (15) |
C8 | 0.0385 (17) | 0.0557 (18) | 0.0481 (15) | 0.0009 (14) | −0.0004 (12) | −0.0002 (13) |
C9 | 0.060 (2) | 0.151 (4) | 0.080 (2) | 0.010 (2) | −0.0213 (18) | −0.031 (2) |
C10 | 0.059 (2) | 0.103 (3) | 0.076 (2) | 0.0165 (19) | 0.0071 (17) | −0.0200 (19) |
C11 | 0.091 (2) | 0.063 (2) | 0.081 (2) | −0.0007 (19) | −0.0015 (18) | −0.0131 (18) |
C12 | 0.059 (2) | 0.0625 (19) | 0.0496 (16) | 0.0101 (15) | −0.0062 (13) | 0.0010 (14) |
C13 | 0.0500 (18) | 0.063 (2) | 0.0404 (15) | −0.0043 (15) | −0.0073 (12) | 0.0002 (15) |
C14 | 0.0520 (19) | 0.063 (2) | 0.0388 (15) | −0.0052 (15) | 0.0005 (12) | −0.0016 (14) |
C15 | 0.054 (2) | 0.064 (2) | 0.0535 (19) | −0.0055 (17) | 0.0008 (14) | −0.0021 (16) |
C16 | 0.100 (3) | 0.077 (2) | 0.073 (2) | 0.005 (2) | 0.0090 (19) | −0.026 (2) |
C17 | 0.194 (5) | 0.076 (3) | 0.109 (3) | 0.047 (3) | 0.008 (3) | −0.010 (2) |
O1—C3 | 1.202 (3) | C6—H6B | 0.9700 |
O2—C13 | 1.357 (3) | C7—C8 | 1.537 (4) |
O2—H2O | 0.93 (3) | C7—H7 | 0.9800 |
O3—C14 | 1.394 (3) | C8—H8 | 0.9800 |
O3—C7 | 1.452 (3) | C9—H9A | 0.9600 |
O4—C15 | 1.231 (3) | C9—H9B | 0.9600 |
O5—C15 | 1.321 (3) | C9—H9C | 0.9600 |
O5—C16 | 1.468 (3) | C10—H10A | 0.9600 |
C1—C12 | 1.530 (3) | C10—H10B | 0.9600 |
C1—C8 | 1.531 (3) | C10—H10C | 0.9600 |
C1—C2 | 1.545 (3) | C11—H11A | 0.9600 |
C1—H1 | 0.9800 | C11—H11B | 0.9600 |
C2—C10 | 1.521 (4) | C11—H11C | 0.9600 |
C2—C3 | 1.522 (4) | C12—C13 | 1.496 (4) |
C2—C11 | 1.553 (4) | C12—H12A | 0.9700 |
C3—C4 | 1.525 (4) | C12—H12B | 0.9700 |
C4—C9 | 1.526 (4) | C13—C14 | 1.343 (4) |
C4—C8 | 1.545 (4) | C14—C15 | 1.462 (4) |
C4—C5 | 1.550 (4) | C16—C17 | 1.465 (5) |
C5—C6 | 1.479 (4) | C16—H16A | 0.9700 |
C5—H5A | 0.9700 | C16—H16B | 0.9700 |
C5—H5B | 0.9700 | C17—H17A | 0.9600 |
C6—C7 | 1.505 (4) | C17—H17B | 0.9600 |
C6—H6A | 0.9700 | C17—H17C | 0.9600 |
C13—O2—H2O | 102 (2) | C4—C8—H8 | 110.7 |
C14—O3—C7 | 113.1 (2) | C4—C9—H9A | 109.5 |
C15—O5—C16 | 116.3 (2) | C4—C9—H9B | 109.5 |
C12—C1—C8 | 112.7 (2) | H9A—C9—H9B | 109.5 |
C12—C1—C2 | 116.1 (2) | C4—C9—H9C | 109.5 |
C8—C1—C2 | 105.5 (2) | H9A—C9—H9C | 109.5 |
C12—C1—H1 | 107.4 | H9B—C9—H9C | 109.5 |
C8—C1—H1 | 107.4 | C2—C10—H10A | 109.5 |
C2—C1—H1 | 107.4 | C2—C10—H10B | 109.5 |
C10—C2—C3 | 112.0 (2) | H10A—C10—H10B | 109.5 |
C10—C2—C1 | 113.9 (2) | C2—C10—H10C | 109.5 |
C3—C2—C1 | 101.9 (2) | H10A—C10—H10C | 109.5 |
C10—C2—C11 | 110.0 (3) | H10B—C10—H10C | 109.5 |
C3—C2—C11 | 105.7 (2) | C2—C11—H11A | 109.5 |
C1—C2—C11 | 112.8 (2) | C2—C11—H11B | 109.5 |
O1—C3—C2 | 124.6 (3) | H11A—C11—H11B | 109.5 |
O1—C3—C4 | 124.6 (3) | C2—C11—H11C | 109.5 |
C2—C3—C4 | 110.8 (2) | H11A—C11—H11C | 109.5 |
C3—C4—C9 | 111.8 (2) | H11B—C11—H11C | 109.5 |
C3—C4—C8 | 104.3 (2) | C13—C12—C1 | 116.0 (2) |
C9—C4—C8 | 115.3 (2) | C13—C12—H12A | 108.3 |
C3—C4—C5 | 110.8 (2) | C1—C12—H12A | 108.3 |
C9—C4—C5 | 112.3 (3) | C13—C12—H12B | 108.3 |
C8—C4—C5 | 101.6 (2) | C1—C12—H12B | 108.3 |
C6—C5—C4 | 106.8 (3) | H12A—C12—H12B | 107.4 |
C6—C5—H5A | 110.4 | C14—C13—O2 | 121.7 (3) |
C4—C5—H5A | 110.4 | C14—C13—C12 | 127.0 (3) |
C6—C5—H5B | 110.4 | O2—C13—C12 | 111.3 (3) |
C4—C5—H5B | 110.4 | C13—C14—O3 | 122.2 (2) |
H5A—C5—H5B | 108.6 | C13—C14—C15 | 120.8 (3) |
C5—C6—C7 | 106.8 (3) | O3—C14—C15 | 117.0 (3) |
C5—C6—H6A | 110.4 | O4—C15—O5 | 123.2 (3) |
C7—C6—H6A | 110.4 | O4—C15—C14 | 122.9 (3) |
C5—C6—H6B | 110.4 | O5—C15—C14 | 114.0 (3) |
C7—C6—H6B | 110.4 | C17—C16—O5 | 107.9 (3) |
H6A—C6—H6B | 108.6 | C17—C16—H16A | 110.1 |
O3—C7—C6 | 109.2 (3) | O5—C16—H16A | 110.1 |
O3—C7—C8 | 111.2 (2) | C17—C16—H16B | 110.1 |
C6—C7—C8 | 107.1 (2) | O5—C16—H16B | 110.1 |
O3—C7—H7 | 109.8 | H16A—C16—H16B | 108.4 |
C6—C7—H7 | 109.8 | C16—C17—H17A | 109.5 |
C8—C7—H7 | 109.8 | C16—C17—H17B | 109.5 |
C1—C8—C7 | 113.5 (2) | H17A—C17—H17B | 109.5 |
C1—C8—C4 | 104.8 (2) | C16—C17—H17C | 109.5 |
C7—C8—C4 | 106.3 (2) | H17A—C17—H17C | 109.5 |
C1—C8—H8 | 110.7 | H17B—C17—H17C | 109.5 |
C7—C8—H8 | 110.7 | ||
C12—C1—C2—C10 | 79.9 (3) | C2—C1—C8—C4 | 35.4 (3) |
C8—C1—C2—C10 | −154.5 (2) | O3—C7—C8—C1 | 16.3 (3) |
C12—C1—C2—C3 | −159.2 (2) | C6—C7—C8—C1 | −103.0 (3) |
C8—C1—C2—C3 | −33.6 (3) | O3—C7—C8—C4 | 131.0 (2) |
C12—C1—C2—C11 | −46.3 (3) | C6—C7—C8—C4 | 11.7 (3) |
C8—C1—C2—C11 | 79.3 (3) | C3—C4—C8—C1 | −22.2 (3) |
C10—C2—C3—O1 | −38.1 (4) | C9—C4—C8—C1 | −145.2 (3) |
C1—C2—C3—O1 | −160.2 (3) | C5—C4—C8—C1 | 93.0 (3) |
C11—C2—C3—O1 | 81.8 (4) | C3—C4—C8—C7 | −142.7 (2) |
C10—C2—C3—C4 | 142.1 (3) | C9—C4—C8—C7 | 94.4 (3) |
C1—C2—C3—C4 | 20.0 (3) | C5—C4—C8—C7 | −27.4 (3) |
C11—C2—C3—C4 | −98.1 (3) | C8—C1—C12—C13 | 49.8 (3) |
O1—C3—C4—C9 | −53.5 (4) | C2—C1—C12—C13 | 171.6 (2) |
C2—C3—C4—C9 | 126.4 (3) | C1—C12—C13—C14 | 8.5 (4) |
O1—C3—C4—C8 | −178.7 (3) | C1—C12—C13—O2 | −169.0 (2) |
C2—C3—C4—C8 | 1.1 (3) | O2—C13—C14—O3 | −177.2 (2) |
O1—C3—C4—C5 | 72.7 (4) | C12—C13—C14—O3 | 5.5 (4) |
C2—C3—C4—C5 | −107.5 (3) | O2—C13—C14—C15 | 1.5 (4) |
C3—C4—C5—C6 | 144.6 (3) | C12—C13—C14—C15 | −175.8 (3) |
C9—C4—C5—C6 | −89.5 (3) | C7—O3—C14—C13 | −75.6 (3) |
C8—C4—C5—C6 | 34.3 (3) | C7—O3—C14—C15 | 105.7 (3) |
C4—C5—C6—C7 | −28.1 (4) | C16—O5—C15—O4 | 1.9 (4) |
C14—O3—C7—C6 | −172.9 (2) | C16—O5—C15—C14 | −178.6 (2) |
C14—O3—C7—C8 | 69.1 (3) | C13—C14—C15—O4 | −6.2 (4) |
C5—C6—C7—O3 | −110.5 (3) | O3—C14—C15—O4 | 172.5 (2) |
C5—C6—C7—C8 | 10.0 (4) | C13—C14—C15—O5 | 174.3 (3) |
C12—C1—C8—C7 | −81.4 (3) | O3—C14—C15—O5 | −7.0 (4) |
C2—C1—C8—C7 | 151.0 (2) | C15—O5—C16—C17 | 167.3 (3) |
C12—C1—C8—C4 | 163.1 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2O···O4 | 0.93 (3) | 1.69 (3) | 2.565 (4) | 155 (3) |
Experimental details
Crystal data | |
Chemical formula | C17H24O5 |
Mr | 308.36 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 291 |
a, b, c (Å) | 8.447 (5), 18.454 (14), 21.735 (15) |
V (Å3) | 3388 (4) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.20 × 0.18 × 0.08 |
Data collection | |
Diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.983, 0.993 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14606, 3153, 1408 |
Rint | 0.087 |
(sin θ/λ)max (Å−1) | 0.606 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.053, 0.149, 0.89 |
No. of reflections | 3153 |
No. of parameters | 207 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.17, −0.17 |
Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 2012), PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2O···O4 | 0.93 (3) | 1.69 (3) | 2.565 (4) | 155 (3) |
Footnotes
‡Present address: School of Chemistry, University of Hyderabad, Hyderabad 500 046, India.
Acknowledgements
We thank the Department of Science and Technology (DST), India, for the CCD facility at the Indian Institute of Science (IISc), Bangalore. CSAK thanks the University Grants Commission for the award of a Dr D. S. Kothari post-doctoral fellowship. GM thanks the Government of India for the award of a National Research Professorship and acknowledges the current research support from the Eli Lilly and Jubilant–Bhartia Foundations.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Rhodium carbenoid mediated O—H insertion provides a facile means of transforming diazo-compounds into diverse range of functionalized ethers (Paulissen, et al., 1973; Cox, et al. 1994; Haigh, 1994; Aller et al., 1995; Shi et al., 1995; Bulugahapitiya et al., 1997; Moody & Miller, 1998; Morton et al., 2012). Hence the methodology has proven to be a useful stratagem in the synthetic acquisition of several natural products (Nelson et al., 2000; Medeiros & Wood, 2010; Freeman, et al. 2010). While not as extensively utilized or studied as the intermolecular variants, intramolecular interception of rhodium carbenoids by hydroxy nucleophiles can, nevertheless, afford an effective route to cyclic ethers and lactones (Paulissen et al., 1974; Moyer et al., 1985; Moody & Taylor, 1987; Heslin & Moody, 1988; Moody et al. 1992; Sarabia-García et al., 1994; Padwa & Sá, 1999; Im et al., 2005). Indeed, studies by Moody and co-workers have shown that rhodium(II) acetate catalysed cyclization in diazoalcohols may even be employed as a practical method for accessing medium-ring oxacycles - oxepanes, in particular, wherein interference from competing C—H insertion reactions do not appear to be significant (Heslin & Moody, 1988; Davies et al., 1990).
Against this background, we report herein the crystal structure of the title compound 1, a 2-carbethoxy-3-oxepanone embedded in a tricyclic framework, that was obtained as the sole isolable product in the rhodium(II) trifluroacetate mediated decomposition of the α-diazo-ω-hydroxy-β-ketoester 2 (Figure 1). Originally envisaged as an entry point to an angularly fused triquinane skeleton via Rh(II) catalyzed intramolecular C—H insertion (Doyle et al., 2010; Davies & Morton, 2011; Srikrishna et al., 2012) en route to the natural product penifulvin A (Shim et al., 2006; Gaich & Mulzer, 2009; Mehta & Khan, 2012), the diazoester 2 was prepared from the β-ketoester 3 via a diazo transfer reaction to the activated methylene group in 3 (Baum et al., 1987).
The crystal structure of 1 was solved and refined in the centrosymmetric orthorhombic space group Pbcn (Z = 8). The 2-carbethoxy-3-oxepanone moiety in 1 was found to exist in the intramolecularly O—H···O hydrogen bonded enol form (Figure 2). As indicated by its puckering parameters (q2 = 0.915 (3) Å, q3 = 0.310 (3) Å, ϕ2 = 193.59 (17)°, ϕ3 = 118.9 (5)°, QT = 0.967 (2) Å), the seven-membered oxacyclic ring adopted a distorted boat-sofa conformation (Cremer & Pople, 1975; Boessenkool & Boeyens, 1980). Crystal packing in 1 was effected primarily via the agency of weak van der Waals interactions, though short C—H···O contacts (C8—H8···O2) could be discerned among the molecules.