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Acta Crystallogr Sect E Struct Rep Online. 2008 May 1; 64(Pt 5): o796.
Published online 2008 April 4. doi:  10.1107/S1600536808006557
PMCID: PMC2961230

(Z)-1,3,4a-Trimethyl-5,5-diphenyl-6-oxa-1,3-diaza­bicyclo­[4.2.0]octane-2,4-dione

Abstract

The title compound, C20H20N2O3, is a head-to-tail oxetane, one of the regioisomers obtained by the the Paternó–Büchi reaction of 1,3-dimethyl­thymine with benzophenone. The oxetane ring is folded, the dihedral angle between the C—O—C and C—C—C planes being 14.4 (2)°. The dihedral angle between the two phenyl rings is 64.3 (2)°. The pyrimidine ring adopts a boat conformation. The crystal structure involves weak C—H(...)O hydrogen bonds.

Related literature

For related literature, see: Hei et al. (2005 [triangle]); Prakash et al. (1997 [triangle]).

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Object name is e-64-0o796-scheme1.jpg

Experimental

Crystal data

  • C20H20N2O3
  • M r = 336.38
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-64-0o796-efi1.jpg
  • a = 8.1341 (7) Å
  • b = 9.1004 (13) Å
  • c = 23.485 (2) Å
  • β = 97.334 (2)°
  • V = 1724.2 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 298 (2) K
  • 0.45 × 0.41 × 0.18 mm

Data collection

  • Bruker SMART diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996 [triangle]) T min = 0.962, T max = 0.984
  • 8774 measured reflections
  • 3039 independent reflections
  • 1818 reflections with I > 2σ(I)
  • R int = 0.036

Refinement

  • R[F 2 > 2σ(F 2)] = 0.044
  • wR(F 2) = 0.117
  • S = 1.01
  • 3039 reflections
  • 226 parameters
  • H-atom parameters constrained
  • Δρmax = 0.20 e Å−3
  • Δρmin = −0.18 e Å−3

Data collection: SMART (Siemens, 1996 [triangle]); cell refinement: SAINT (Siemens, 1996 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808006557/wn2239sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808006557/wn2239Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

This work was supported by the Grants for Scientific Research of BSKY (grant No. XJ200712) from Anhui Medical University.

supplementary crystallographic information

Comment

A [2 + 2] photocycloaddition (Paternò-Büchi reaction) of the 5–6 double bond of 1,3-dimethylthymine (DMT) with the carbonyl of benzophenone generates two regioisomers, head-to-head and head-to-tail oxetanes (Fig. 1). We have observed the temperature dependence of the regioselectivity (Hei et al., 2005). The crystal structure of the head-to-head oxetane has already been published (Prakash et al., 1997). In the present study, an X-ray crystallographic analysis of the head-to-tail oxetane has been undertaken to establish its structure and configuration.

The structure is similar to that observed in the head-to-head oxetane (Prakash et al., 1997). The bond lengths and angles in the title compound are in good agreement with expected values. The oxetane ring is folded and the dihedral angle between the C1—O1—C3 and C1—C2—C3 planes is 14.4 (2)° (Fig. 2). The dihedral angle between the two phenyl rings is 64.3 (2)° and the pyrimidine ring adopts a boat conformation. The crystal structure involves weak C—H···O hydrogen bonds.

Experimental

The title compound was prepared by first dissolving DMT (0.77 g, 5.0 mmol) and benzophenone (1.82 g, 10.0 mmol) in CH3CN (100 ml). The resulting solution was placed in a photochemical apparatus (Pyrex), purged with nitrogen, degassed for 30 min, and irradiated with a 300 W mercury high-pressure lamp for 10 h. The solvent was then rotary evaporated and the oxetane was purified by silica gel chromatography using a 4:1 petroleum ether/ethyl acetate solvent mixture. The fractions containing the h-t oxetane were combined, and the solvent removed by rotary evaporation. The purified oxetane was subsequently crystallized by dissolving the residue in 10 ml of ethyl acetate and adding n-hexane to the solution until it turned cloudy. Upon standing at room temperature, a colorless block appeared and was separated from the solvent by decanting.

Refinement

All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.98 Å (methine), 0.96 Å (methyl) and 0.93 Å (aromatic); Uiso(H) = 1.2 Ueq(C, O) or 1.5 Ueq(C) for the methyl group.

Figures

Fig. 1.
Formation of the two regioisomers of the Paternó-Büchi reaction.
Fig. 2.
Molecular structure of the title compound, with the atomic numbering scheme, and displacement ellipsoids drawn at the 30% probability level.

Crystal data

C20H20N2O3F000 = 712
Mr = 336.38Dx = 1.296 Mg m3
Monoclinic, P21/nMo Kα radiation λ = 0.71073 Å
a = 8.1341 (7) ÅCell parameters from 1952 reflections
b = 9.1004 (13) Åθ = 2.4–22.1º
c = 23.485 (2) ŵ = 0.09 mm1
β = 97.334 (2)ºT = 298 (2) K
V = 1724.2 (3) Å3Block, colorless
Z = 40.45 × 0.41 × 0.18 mm

Data collection

Bruker SMART diffractometer3039 independent reflections
Radiation source: fine-focus sealed tube1818 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.036
T = 298(2) Kθmax = 25.0º
[var phi] and ω scansθmin = 1.8º
Absorption correction: multi-scan(SADABS; Sheldrick, 1996)h = −9→9
Tmin = 0.962, Tmax = 0.984k = −10→10
8774 measured reflectionsl = −24→27

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044H-atom parameters constrained
wR(F2) = 0.117  w = 1/[σ2(Fo2) + (0.038P)2 + 0.7238P] where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
3039 reflectionsΔρmax = 0.20 e Å3
226 parametersΔρmin = −0.18 e Å3
Primary atom site location: structure-invariant direct methodsExtinction correction: none

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

xyzUiso*/Ueq
N11.2692 (2)0.5663 (2)0.21196 (8)0.0491 (5)
N21.2831 (2)0.6885 (2)0.12510 (8)0.0492 (5)
O10.97763 (19)0.60800 (17)0.19685 (6)0.0469 (4)
O21.4490 (2)0.7527 (2)0.20642 (8)0.0750 (6)
O31.1732 (2)0.5833 (2)0.04218 (7)0.0625 (5)
C10.9036 (3)0.5849 (2)0.13794 (8)0.0379 (5)
C21.0673 (3)0.4991 (2)0.12589 (9)0.0380 (5)
C31.1126 (3)0.5076 (3)0.19078 (9)0.0427 (6)
H31.09490.41270.20880.051*
C41.3391 (3)0.6743 (3)0.18356 (11)0.0503 (6)
C51.1782 (3)0.5906 (3)0.09400 (10)0.0440 (6)
C60.7544 (3)0.4834 (2)0.13563 (9)0.0398 (6)
C70.7166 (3)0.4145 (3)0.18451 (11)0.0555 (7)
H70.77810.43580.21970.067*
C80.5890 (4)0.3147 (3)0.18183 (13)0.0654 (8)
H80.56460.26950.21530.079*
C90.4977 (3)0.2812 (3)0.13056 (13)0.0617 (8)
H90.41280.21240.12890.074*
C100.5325 (3)0.3502 (3)0.08148 (12)0.0580 (7)
H100.47010.32890.04650.070*
C110.6592 (3)0.4506 (3)0.08398 (10)0.0481 (6)
H110.68150.49710.05060.058*
C120.8626 (3)0.7299 (2)0.10882 (9)0.0385 (6)
C130.8285 (3)0.8494 (3)0.14167 (11)0.0505 (6)
H130.83360.83920.18130.061*
C140.7872 (4)0.9835 (3)0.11655 (14)0.0673 (8)
H140.76451.06290.13920.081*
C150.7794 (4)0.9999 (3)0.05856 (14)0.0727 (9)
H150.75231.09060.04170.087*
C160.8116 (4)0.8830 (3)0.02531 (12)0.0666 (8)
H160.80610.8942−0.01420.080*
C170.8520 (3)0.7485 (3)0.05001 (10)0.0504 (6)
H170.87240.66930.02690.060*
C181.0451 (3)0.3473 (3)0.09951 (10)0.0503 (6)
H18A0.98860.35520.06120.075*
H18B0.98090.28770.12220.075*
H18C1.15170.30290.09850.075*
C191.3263 (4)0.5493 (3)0.27297 (11)0.0783 (9)
H19A1.44320.56830.27990.117*
H19B1.30460.45080.28470.117*
H19C1.26860.61750.29450.117*
C201.3705 (4)0.7944 (3)0.09317 (13)0.0803 (10)
H20A1.45390.74450.07510.121*
H20B1.42180.86760.11900.121*
H20C1.29310.84080.06440.121*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
N10.0490 (13)0.0549 (13)0.0392 (12)0.0034 (11)−0.0110 (9)−0.0031 (10)
N20.0448 (12)0.0524 (13)0.0499 (13)−0.0048 (10)0.0035 (10)−0.0005 (10)
O10.0509 (10)0.0554 (11)0.0329 (9)0.0088 (8)−0.0009 (7)−0.0072 (7)
O20.0666 (13)0.0819 (14)0.0730 (13)−0.0225 (12)−0.0044 (11)−0.0256 (11)
O30.0560 (12)0.0921 (14)0.0402 (11)−0.0015 (10)0.0092 (8)−0.0015 (9)
C10.0403 (14)0.0433 (14)0.0290 (12)0.0050 (11)0.0004 (10)−0.0041 (10)
C20.0387 (13)0.0403 (13)0.0336 (12)0.0042 (11)−0.0008 (10)−0.0043 (10)
C30.0467 (15)0.0395 (14)0.0402 (14)0.0043 (12)−0.0011 (11)−0.0030 (11)
C40.0450 (15)0.0526 (17)0.0519 (16)0.0041 (13)0.0012 (13)−0.0122 (13)
C50.0377 (14)0.0522 (16)0.0414 (15)0.0069 (12)0.0024 (11)−0.0021 (12)
C60.0379 (13)0.0414 (14)0.0405 (14)0.0063 (11)0.0067 (11)0.0006 (11)
C70.0573 (17)0.0665 (18)0.0442 (15)−0.0029 (15)0.0119 (12)0.0020 (13)
C80.0656 (19)0.070 (2)0.065 (2)−0.0033 (16)0.0253 (16)0.0127 (15)
C90.0438 (16)0.0573 (18)0.085 (2)−0.0021 (14)0.0134 (15)0.0074 (16)
C100.0402 (15)0.0623 (18)0.0680 (19)−0.0026 (14)−0.0062 (13)0.0037 (15)
C110.0447 (15)0.0519 (16)0.0467 (15)−0.0002 (13)0.0015 (12)0.0076 (12)
C120.0324 (13)0.0391 (14)0.0434 (14)0.0010 (10)0.0027 (10)−0.0035 (11)
C130.0477 (15)0.0505 (16)0.0512 (15)0.0059 (13)−0.0016 (12)−0.0098 (13)
C140.073 (2)0.0418 (16)0.083 (2)0.0119 (14)−0.0031 (16)−0.0150 (15)
C150.087 (2)0.0434 (17)0.083 (2)0.0064 (15)−0.0078 (18)0.0103 (16)
C160.089 (2)0.0519 (18)0.0564 (17)0.0058 (16)−0.0001 (15)0.0085 (14)
C170.0587 (17)0.0438 (15)0.0483 (16)0.0068 (13)0.0059 (12)0.0010 (12)
C180.0462 (15)0.0501 (15)0.0524 (15)0.0065 (12)−0.0026 (12)−0.0129 (12)
C190.082 (2)0.095 (2)0.0493 (17)−0.0024 (19)−0.0221 (15)0.0001 (16)
C200.078 (2)0.082 (2)0.082 (2)−0.0240 (18)0.0150 (18)0.0105 (17)

Geometric parameters (Å, °)

N1—C41.353 (3)C9—H90.9300
N1—C31.412 (3)C10—C111.373 (3)
N1—C191.457 (3)C10—H100.9300
N2—C51.377 (3)C11—H110.9300
N2—C41.396 (3)C12—C131.381 (3)
N2—C201.460 (3)C12—C171.383 (3)
O1—C31.450 (3)C13—C141.379 (4)
O1—C11.452 (2)C13—H130.9300
O2—C41.214 (3)C14—C151.364 (4)
O3—C51.214 (3)C14—H140.9300
C1—C121.504 (3)C15—C161.365 (4)
C1—C61.521 (3)C15—H150.9300
C1—C21.600 (3)C16—C171.376 (3)
C2—C51.497 (3)C16—H160.9300
C2—C181.515 (3)C17—H170.9300
C2—C31.523 (3)C18—H18A0.9600
C3—H30.9800C18—H18B0.9600
C6—C71.376 (3)C18—H18C0.9600
C6—C111.386 (3)C19—H19A0.9600
C7—C81.375 (4)C19—H19B0.9600
C7—H70.9300C19—H19C0.9600
C8—C91.366 (4)C20—H20A0.9600
C8—H80.9300C20—H20B0.9600
C9—C101.373 (4)C20—H20C0.9600
C4—N1—C3121.2 (2)C11—C10—C9120.2 (3)
C4—N1—C19117.4 (2)C11—C10—H10119.9
C3—N1—C19117.8 (2)C9—C10—H10119.9
C5—N2—C4124.3 (2)C10—C11—C6120.9 (2)
C5—N2—C20117.6 (2)C10—C11—H11119.6
C4—N2—C20116.6 (2)C6—C11—H11119.6
C3—O1—C192.41 (14)C13—C12—C17118.0 (2)
O1—C1—C12110.28 (17)C13—C12—C1119.0 (2)
O1—C1—C6110.74 (17)C17—C12—C1122.9 (2)
C12—C1—C6112.78 (18)C14—C13—C12120.9 (2)
O1—C1—C289.20 (14)C14—C13—H13119.6
C12—C1—C2119.28 (18)C12—C13—H13119.6
C6—C1—C2112.08 (17)C15—C14—C13120.1 (3)
C5—C2—C18110.54 (19)C15—C14—H14119.9
C5—C2—C3112.83 (19)C13—C14—H14119.9
C18—C2—C3117.16 (19)C14—C15—C16119.9 (3)
C5—C2—C1112.63 (18)C14—C15—H15120.1
C18—C2—C1117.30 (18)C16—C15—H15120.1
C3—C2—C184.20 (15)C15—C16—C17120.3 (3)
N1—C3—O1112.77 (18)C15—C16—H16119.8
N1—C3—C2117.63 (19)C17—C16—H16119.8
O1—C3—C292.34 (15)C16—C17—C12120.7 (2)
N1—C3—H3110.9C16—C17—H17119.6
O1—C3—H3110.9C12—C17—H17119.6
C2—C3—H3110.9C2—C18—H18A109.5
O2—C4—N1122.7 (2)C2—C18—H18B109.5
O2—C4—N2120.6 (3)H18A—C18—H18B109.5
N1—C4—N2116.6 (2)C2—C18—H18C109.5
O3—C5—N2120.4 (2)H18A—C18—H18C109.5
O3—C5—C2121.7 (2)H18B—C18—H18C109.5
N2—C5—C2117.8 (2)N1—C19—H19A109.5
C7—C6—C11118.2 (2)N1—C19—H19B109.5
C7—C6—C1120.6 (2)H19A—C19—H19B109.5
C11—C6—C1121.07 (19)N1—C19—H19C109.5
C8—C7—C6120.7 (2)H19A—C19—H19C109.5
C8—C7—H7119.7H19B—C19—H19C109.5
C6—C7—H7119.7N2—C20—H20A109.5
C9—C8—C7120.7 (3)N2—C20—H20B109.5
C9—C8—H8119.7H20A—C20—H20B109.5
C7—C8—H8119.7N2—C20—H20C109.5
C8—C9—C10119.4 (3)H20A—C20—H20C109.5
C8—C9—H9120.3H20B—C20—H20C109.5
C10—C9—H9120.3
C3—O1—C1—C12−131.48 (18)C20—N2—C5—C2−170.0 (2)
C3—O1—C1—C6102.98 (19)C18—C2—C5—O337.6 (3)
C3—O1—C1—C2−10.39 (16)C3—C2—C5—O3170.9 (2)
O1—C1—C2—C5−102.41 (19)C1—C2—C5—O3−95.8 (3)
C12—C1—C2—C510.5 (3)C18—C2—C5—N2−144.8 (2)
C6—C1—C2—C5145.47 (19)C3—C2—C5—N2−11.4 (3)
O1—C1—C2—C18127.57 (19)C1—C2—C5—N281.9 (2)
C12—C1—C2—C18−119.5 (2)O1—C1—C6—C7−6.9 (3)
C6—C1—C2—C1815.5 (3)C12—C1—C6—C7−131.1 (2)
O1—C1—C2—C39.93 (15)C2—C1—C6—C791.0 (2)
C12—C1—C2—C3122.9 (2)O1—C1—C6—C11177.12 (19)
C6—C1—C2—C3−102.19 (18)C12—C1—C6—C1153.0 (3)
C4—N1—C3—O1−72.4 (3)C2—C1—C6—C11−85.0 (2)
C19—N1—C3—O185.8 (3)C11—C6—C7—C80.7 (4)
C4—N1—C3—C233.3 (3)C1—C6—C7—C8−175.3 (2)
C19—N1—C3—C2−168.6 (2)C6—C7—C8—C90.3 (4)
C1—O1—C3—N1132.30 (19)C7—C8—C9—C10−1.1 (4)
C1—O1—C3—C210.93 (17)C8—C9—C10—C110.7 (4)
C5—C2—C3—N1−15.1 (3)C9—C10—C11—C60.4 (4)
C18—C2—C3—N1115.0 (2)C7—C6—C11—C10−1.1 (3)
C1—C2—C3—N1−127.2 (2)C1—C6—C11—C10174.9 (2)
C5—C2—C3—O1102.19 (19)O1—C1—C12—C13−27.7 (3)
C18—C2—C3—O1−127.7 (2)C6—C1—C12—C1396.7 (2)
C1—C2—C3—O1−9.95 (15)C2—C1—C12—C13−128.7 (2)
C3—N1—C4—O2160.5 (2)O1—C1—C12—C17154.5 (2)
C19—N1—C4—O22.3 (4)C6—C1—C12—C17−81.1 (3)
C3—N1—C4—N2−22.0 (3)C2—C1—C12—C1753.5 (3)
C19—N1—C4—N2179.8 (2)C17—C12—C13—C14−0.8 (4)
C5—N2—C4—O2169.6 (2)C1—C12—C13—C14−178.7 (2)
C20—N2—C4—O23.8 (3)C12—C13—C14—C150.0 (4)
C5—N2—C4—N1−7.9 (3)C13—C14—C15—C160.5 (5)
C20—N2—C4—N1−173.7 (2)C14—C15—C16—C17−0.1 (5)
C4—N2—C5—O3−157.9 (2)C15—C16—C17—C12−0.7 (4)
C20—N2—C5—O37.7 (3)C13—C12—C17—C161.2 (4)
C4—N2—C5—C224.4 (3)C1—C12—C17—C16179.0 (2)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C3—H3···O2i0.982.533.431 (3)153
C7—H7···O10.932.372.745 (3)104
C8—H8···O1ii0.932.593.513 (3)171
C13—H13···O10.932.412.752 (3)101
C17—H17···O30.932.553.040 (3)113
C20—H20B···O20.962.292.682 (4)104

Symmetry codes: (i) −x+5/2, y−1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WN2239).

References

  • Hei, X. M., Song, Q. H., Tang, W. J., Wang, H. B. & Guo, Q. X. (2005). J. Org. Chem.70, 2522–2527. [PubMed]
  • Prakash, G., Fettinger, J. C. & Falvey, D. E. (1997). Acta Cryst. C53, 979–981.
  • Sheldrick, G. M. (1996). SADABS University of Göttingen, Germany.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Siemens (1996). SMART and SAINT Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.

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