organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

(Z)-Methyl 2-meth­oxy­imino-3-oxo­butanoate

aFakultät Chemie, Technische Universität Dortmund, Otto-Hahn-Strasse 6, 44221 Dortmund, Germany, and bMax-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44221 Dortmund, Germany
*Correspondence e-mail: hans.preut@udo.edu, hans-dieter.arndt@mpi-dortmund.mpg.de

(Received 31 January 2008; accepted 13 February 2008; online 15 February 2008)

The title compound, C6H9NO4, was prepared stereoselectively as a precursor for 1-aza­dienes in a study of hetero-Diels–Alder reactions. The configuration of the C=N double bond was found to be Z, corroborating earlier assignments of similar compounds based only on NMR and IR spectroscopic analysis.

Related literature

For related literature, see: Buehler (1967[Buehler, E. (1967). J. Org. Chem. 32, 261-265.]); Corrêa & Moran (1999[Corrêa, I. R. Jr & Moran, P. J. S. (1999). Tetrahedron, 55, 14221-14232.]); Fletcher et al. (2006[Fletcher, M. D., Hurst, T. E., Miles, T. J. & Moody, C. J. (2006). Tetrahedron, 62, 5454-5463.]); François et al. (2004[François, D., Madden, A. & Murray, W. V. (2004). Org. Lett. 6, 1931-1934.]); Jirman et al. (1990[Jirman, J., Lycka, A. & Ludwig, M. (1990). Collect. Czech. Chem. Commun. 55, 136-146.]); Karabatsos & Taller (1968[Karabatsos, G. J. & Taller, R. A. (1968). Tetrahedron, 24, 3347-3360.]); Levy & Nelson (1972[Levy, G. C. & Nelson, G. L. (1972). J. Am. Chem. Soc. 94, 4897-4901.]); Lu & Arndt (2007[Lu, J.-Y. & Arndt, H.-D. (2007). J. Org. Chem. 72, 4205-4212.]).

[Scheme 1]

Experimental

Crystal data
  • C6H9NO4

  • Mr = 159.14

  • Orthorhombic, P n a 21

  • a = 8.3410 (17) Å

  • b = 13.410 (3) Å

  • c = 7.2900 (15) Å

  • V = 815.4 (3) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.11 mm−1

  • T = 291 (1) K

  • 0.2 × 0.2 × 0.2 mm

Data collection
  • Nonius KappaCCD diffractometer

  • Absorption correction: none

  • 3104 measured reflections

  • 899 independent reflections

  • 536 reflections with I > 2σ(I)

  • Rint = 0.045

Refinement
  • R[F2 > 2σ(F2)] = 0.027

  • wR(F2) = 0.057

  • S = 1.09

  • 899 reflections

  • 104 parameters

  • 1 restraint

  • H-atom parameters constrained

  • Δρmax = 0.08 e Å−3

  • Δρmin = −0.11 e Å−3

Data collection: COLLECT (Nonius, 1998[Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL-Plus (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]).

Supporting information


Comment top

Oxime geometry has been found to be important for determining their reactivity in cycloadditions and pericyclic reactions (e.g. François et al., 2004). The title compound, (I), was prepared in the study of hetero-Diels–Alder reactions to form 3-hydroxy-pyridines (Lu & Arndt, 2007; Fletcher et al., 2006).

The crystal structure of (I) (Fig. 1) verifies earlier studies by NMR and IR (Buehler, 1967; Karabatsos & Taller, 1968; Levy & Nelson, 1972; Jirman et al., 1990; Corrêa & Moran, 1999) of Z-configured oximes and forms a basis for further studies in the field. Interestingly, the C1/O2/O4 carboxyl group in (I) adopts a dihedral angle of 93° with respect to the coplanar N?C—C?O π-system, which indicates complete absence of electronic conjugation.

Related literature top

For related literature, see: Buehler (1967); Corrêa & Moran (1999); Fletcher et al. (2006); François et al. (2004); Jirman et al. (1990); Karabatsos & Taller (1968); Levy & Nelson (1972); Lu & Arndt (2007).

Experimental top

A stirred solution of 7.25 g (50.0 mmol) of Z-Methyl 2-(hydroxyimino)-3-oxobutanoate (Lu & Arndt, 2007; Fletcher et al., 2006) in anhydrous acetone (50 ml) was cooled to 273 K and potassium carbonate (3.8 g, 27.5 mmol) was added, followed by dimethyl sulfate (5.70 ml, 60.0 mmol). The stirred reaction mixture was warmed to room temperature over 2 h and kept stirring for 10 h (TLC control). The reaction mixture was filtered and the solid residue was rinsed with acetone (3 × 10 ml). The combined filtrates were evaporated to dryness, redissolved in Et2O (100 ml), washed with sat. NaCl solution (3 × 40 ml) and dried with Na2SO4. Concentration and purification by column chromatography (100 g SiO2, EtOAc/light petroleum v/v = 1:8) gave 7.60 g (47.8 mmol, 96%) of the title compound as a colourless oil which crystallized on standing as colourless cubes.

Mp = 335–337 K; Rf = 0.46 (SiO2, EtOAc/cyclohexane = 1:2); 1H NMR (400 MHz, CDCl3) δ = 2.38 (3H, s, C(O)CH3), 3.85 (3H, s, =NOCH3), 4.08 (3H, s, COOCH3); 13C NMR (100.6 MHz, CDCl3) δ = 25.1 (C(O)CH3), 52.5 (COOCH3), 64.4 (NOCH3), 149.9 (C=N), 161.5 (COOCH3), 192.7 (C(O)CH3); IR (KBr): ν = 3009w, 2951w, 1744 s, 1683 s, 1596 s, 1241 s, 1021 s, 841 s cm-1; HRMS (EI): m/Z calc. for C6H9NO4 [M+]: 159.0532, found: 159.0524.

Refinement top

Anomalous dispersion was negligible and Friedel pairs were merged before refinement.

The H atoms were placed in calculated positions, with C—H = 0.96 Å and were refined as riding, with Uiso(H) = 1.5Ueq(C); the methyl groups were allowed to rotate but not to tip.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with displacement ellipsoids shown at the 30% probability level (arbitrary spheres for the H atoms).
(Z)-Methyl 2-methoxyimino-3-oxobutanoate top
Crystal data top
C6H9NO4F(000) = 336
Mr = 159.14Dx = 1.296 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 3104 reflections
a = 8.3410 (17) Åθ = 3.0–27.5°
b = 13.410 (3) ŵ = 0.11 mm1
c = 7.2900 (15) ÅT = 291 K
V = 815.4 (3) Å3Cube, colourless
Z = 40.2 × 0.2 × 0.2 mm
Data collection top
Nonius KappaCCD
diffractometer
536 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.045
Graphite monochromatorθmax = 26.4°, θmin = 3.9°
Detector resolution: 19 vertical, 18 horizontal pixels mm-1h = 1010
213 frames via ω–rotation (Δω = 1%) and two times 40 s per frame (four sets at different κ–angles) scansk = 1616
3104 measured reflectionsl = 99
899 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.027H-atom parameters constrained
wR(F2) = 0.057 w = 1/[σ2(Fo2) + (0.0206P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max < 0.001
899 reflectionsΔρmax = 0.08 e Å3
104 parametersΔρmin = 0.11 e Å3
1 restraintExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.087 (6)
Crystal data top
C6H9NO4V = 815.4 (3) Å3
Mr = 159.14Z = 4
Orthorhombic, Pna21Mo Kα radiation
a = 8.3410 (17) ŵ = 0.11 mm1
b = 13.410 (3) ÅT = 291 K
c = 7.2900 (15) Å0.2 × 0.2 × 0.2 mm
Data collection top
Nonius KappaCCD
diffractometer
536 reflections with I > 2σ(I)
3104 measured reflectionsRint = 0.045
899 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0271 restraint
wR(F2) = 0.057H-atom parameters constrained
S = 1.09Δρmax = 0.08 e Å3
899 reflectionsΔρmin = 0.11 e Å3
104 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.14686 (19)0.12432 (11)0.8457 (2)0.0633 (5)
O20.1931 (2)0.03995 (12)0.4285 (2)0.0784 (6)
O30.4017 (2)0.23981 (12)0.3446 (3)0.0923 (7)
O40.4114 (2)0.03491 (11)0.6049 (2)0.0634 (5)
N10.19750 (19)0.20788 (12)0.7495 (3)0.0536 (5)
C10.2847 (3)0.07762 (15)0.5349 (3)0.0520 (6)
C30.2673 (2)0.18321 (15)0.5998 (3)0.0463 (5)
C50.3291 (3)0.26405 (17)0.4804 (3)0.0557 (6)
C70.0702 (3)0.15466 (19)1.0136 (3)0.0749 (8)
H7A0.03490.09671.07960.112*
H7B0.02050.19610.98570.112*
H7C0.14490.19141.08750.112*
C80.4383 (4)0.06865 (16)0.5537 (3)0.0819 (9)
H8A0.52260.09600.62790.123*
H8D0.46830.07210.42680.123*
H8B0.34160.10610.57270.123*
C90.3008 (3)0.37018 (15)0.5307 (4)0.0674 (7)
H9A0.34810.41280.43970.101*
H9B0.34840.38360.64800.101*
H9D0.18750.38260.53670.101*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0881 (11)0.0498 (9)0.0519 (9)0.0045 (8)0.0208 (9)0.0002 (9)
O20.0868 (13)0.0657 (11)0.0828 (13)0.0028 (9)0.0205 (12)0.0202 (11)
O30.1322 (17)0.0691 (12)0.0755 (13)0.0101 (10)0.0492 (14)0.0068 (11)
O40.0676 (10)0.0551 (9)0.0675 (10)0.0137 (8)0.0078 (9)0.0037 (9)
N10.0625 (12)0.0471 (11)0.0510 (12)0.0028 (9)0.0046 (12)0.0004 (10)
C10.0601 (14)0.0494 (13)0.0467 (14)0.0018 (13)0.0041 (14)0.0023 (13)
C30.0483 (12)0.0491 (13)0.0415 (12)0.0010 (10)0.0001 (12)0.0037 (12)
C50.0615 (16)0.0567 (15)0.0490 (14)0.0031 (12)0.0063 (13)0.0008 (13)
C70.0981 (19)0.0731 (17)0.0535 (16)0.0063 (16)0.0276 (15)0.0040 (14)
C80.1075 (19)0.0597 (17)0.079 (2)0.0278 (14)0.0040 (16)0.0008 (15)
C90.0773 (15)0.0517 (14)0.0732 (17)0.0057 (13)0.0087 (13)0.0009 (15)
Geometric parameters (Å, º) top
O1—N11.387 (2)C7—H7A0.9600
O1—C71.440 (3)C7—H7B0.9600
O2—C11.200 (3)C7—H7C0.9600
O3—C51.205 (3)C8—H8A0.9600
O4—C11.306 (3)C8—H8D0.9600
O4—C81.455 (2)C8—H8B0.9600
N1—C31.281 (3)C9—H9A0.9600
C1—C31.500 (3)C9—H9B0.9600
C3—C51.483 (3)C9—H9D0.9600
C5—C91.489 (3)
N1—O1—C7109.67 (16)O1—C7—H7C109.5
C1—O4—C8116.29 (19)H7A—C7—H7C109.5
C3—N1—O1111.12 (17)H7B—C7—H7C109.5
O2—C1—O4125.7 (2)O4—C8—H8A109.5
O2—C1—C3122.6 (2)O4—C8—H8D109.5
O4—C1—C3111.7 (2)H8A—C8—H8D109.5
N1—C3—C5118.01 (19)O4—C8—H8B109.5
N1—C3—C1123.8 (2)H8A—C8—H8B109.5
C5—C3—C1118.1 (2)H8D—C8—H8B109.5
O3—C5—C3117.4 (2)C5—C9—H9A109.5
O3—C5—C9122.7 (2)C5—C9—H9B109.5
C3—C5—C9119.9 (2)H9A—C9—H9B109.5
O1—C7—H7A109.5C5—C9—H9D109.5
O1—C7—H7B109.5H9A—C9—H9D109.5
H7A—C7—H7B109.5H9B—C9—H9D109.5

Experimental details

Crystal data
Chemical formulaC6H9NO4
Mr159.14
Crystal system, space groupOrthorhombic, Pna21
Temperature (K)291
a, b, c (Å)8.3410 (17), 13.410 (3), 7.2900 (15)
V3)815.4 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.2 × 0.2 × 0.2
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3104, 899, 536
Rint0.045
(sin θ/λ)max1)0.625
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.027, 0.057, 1.09
No. of reflections899
No. of parameters104
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.08, 0.11

Computer programs: COLLECT (Nonius, 1998), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXTL-Plus (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2003).

 

Acknowledgements

Funding by the Deutsche Forschungsgemeinschaft (Emmy–Noether grant Nos. AR493-1 and -2 to HDA), the Fonds der Chemischen Industrie, and the IMPRS Chemical Biology (to JYL and WZS) is gratefully acknowledged.

References

First citationBuehler, E. (1967). J. Org. Chem. 32, 261–265.  CrossRef CAS Web of Science Google Scholar
First citationCorrêa, I. R. Jr & Moran, P. J. S. (1999). Tetrahedron, 55, 14221–14232.  Google Scholar
First citationFletcher, M. D., Hurst, T. E., Miles, T. J. & Moody, C. J. (2006). Tetrahedron, 62, 5454–5463.  Web of Science CrossRef CAS Google Scholar
First citationFrançois, D., Madden, A. & Murray, W. V. (2004). Org. Lett. 6, 1931–1934.  Web of Science PubMed Google Scholar
First citationJirman, J., Lycka, A. & Ludwig, M. (1990). Collect. Czech. Chem. Commun. 55, 136–146.  CrossRef CAS Google Scholar
First citationKarabatsos, G. J. & Taller, R. A. (1968). Tetrahedron, 24, 3347–3360.  CrossRef CAS Web of Science Google Scholar
First citationLevy, G. C. & Nelson, G. L. (1972). J. Am. Chem. Soc. 94, 4897–4901.  CrossRef CAS Web of Science Google Scholar
First citationLu, J.-Y. & Arndt, H.-D. (2007). J. Org. Chem. 72, 4205–4212.  Web of Science CrossRef PubMed CAS Google Scholar
First citationNonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.  Google Scholar
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2003). J. Appl. Cryst. 36, 7–13.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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