organic compounds
(Z)-1,3,4a-Trimethyl-5,5-diphenyl-6-oxa-1,3-diazabicyclo[4.2.0]octane-2,4-dione
aSchool of Pharmacy, Anhui Medical University, Hefei 230032, People's Republic of China
*Correspondence e-mail: tangwjster@gmail.com
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 involves weak C—H⋯O hydrogen bonds.
Experimental
Crystal data
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Refinement
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Data collection: SMART (Siemens, 1996); cell SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536808006557/wn2239sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808006557/wn2239Isup2.hkl
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
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.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.
Data collection: SMART (Siemens, 1996); cell
SAINT (Siemens, 1996); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C20H20N2O3 | F(000) = 712 |
Mr = 336.38 | Dx = 1.296 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 8.1341 (7) Å | Cell parameters from 1952 reflections |
b = 9.1004 (13) Å | θ = 2.4–22.1° |
c = 23.485 (2) Å | µ = 0.09 mm−1 |
β = 97.334 (2)° | T = 298 K |
V = 1724.2 (3) Å3 | Block, colorless |
Z = 4 | 0.45 × 0.41 × 0.18 mm |
Bruker SMART diffractometer | 3039 independent reflections |
Radiation source: fine-focus sealed tube | 1818 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.036 |
ϕ and ω scans | θmax = 25.0°, θmin = 1.8° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −9→9 |
Tmin = 0.962, Tmax = 0.984 | k = −10→10 |
8774 measured reflections | l = −24→27 |
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)] = 0.044 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.038P)2 + 0.7238P] where P = (Fo2 + 2Fc2)/3 |
3039 reflections | (Δ/σ)max < 0.001 |
226 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
C20H20N2O3 | V = 1724.2 (3) Å3 |
Mr = 336.38 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 8.1341 (7) Å | µ = 0.09 mm−1 |
b = 9.1004 (13) Å | T = 298 K |
c = 23.485 (2) Å | 0.45 × 0.41 × 0.18 mm |
β = 97.334 (2)° |
Bruker SMART diffractometer | 3039 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1818 reflections with I > 2σ(I) |
Tmin = 0.962, Tmax = 0.984 | Rint = 0.036 |
8774 measured reflections |
R[F2 > 2σ(F2)] = 0.044 | 0 restraints |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.20 e Å−3 |
3039 reflections | Δρmin = −0.18 e Å−3 |
226 parameters |
x | y | z | Uiso*/Ueq | ||
N1 | 1.2692 (2) | 0.5663 (2) | 0.21196 (8) | 0.0491 (5) | |
N2 | 1.2831 (2) | 0.6885 (2) | 0.12510 (8) | 0.0492 (5) | |
O1 | 0.97763 (19) | 0.60800 (17) | 0.19685 (6) | 0.0469 (4) | |
O2 | 1.4490 (2) | 0.7527 (2) | 0.20642 (8) | 0.0750 (6) | |
O3 | 1.1732 (2) | 0.5833 (2) | 0.04218 (7) | 0.0625 (5) | |
C1 | 0.9036 (3) | 0.5849 (2) | 0.13794 (8) | 0.0379 (5) | |
C2 | 1.0673 (3) | 0.4991 (2) | 0.12589 (9) | 0.0380 (5) | |
C3 | 1.1126 (3) | 0.5076 (3) | 0.19078 (9) | 0.0427 (6) | |
H3 | 1.0949 | 0.4127 | 0.2088 | 0.051* | |
C4 | 1.3391 (3) | 0.6743 (3) | 0.18356 (11) | 0.0503 (6) | |
C5 | 1.1782 (3) | 0.5906 (3) | 0.09400 (10) | 0.0440 (6) | |
C6 | 0.7544 (3) | 0.4834 (2) | 0.13563 (9) | 0.0398 (6) | |
C7 | 0.7166 (3) | 0.4145 (3) | 0.18451 (11) | 0.0555 (7) | |
H7 | 0.7781 | 0.4358 | 0.2197 | 0.067* | |
C8 | 0.5890 (4) | 0.3147 (3) | 0.18183 (13) | 0.0654 (8) | |
H8 | 0.5646 | 0.2695 | 0.2153 | 0.079* | |
C9 | 0.4977 (3) | 0.2812 (3) | 0.13056 (13) | 0.0617 (8) | |
H9 | 0.4128 | 0.2124 | 0.1289 | 0.074* | |
C10 | 0.5325 (3) | 0.3502 (3) | 0.08148 (12) | 0.0580 (7) | |
H10 | 0.4701 | 0.3289 | 0.0465 | 0.070* | |
C11 | 0.6592 (3) | 0.4506 (3) | 0.08398 (10) | 0.0481 (6) | |
H11 | 0.6815 | 0.4971 | 0.0506 | 0.058* | |
C12 | 0.8626 (3) | 0.7299 (2) | 0.10882 (9) | 0.0385 (6) | |
C13 | 0.8285 (3) | 0.8494 (3) | 0.14167 (11) | 0.0505 (6) | |
H13 | 0.8336 | 0.8392 | 0.1813 | 0.061* | |
C14 | 0.7872 (4) | 0.9835 (3) | 0.11655 (14) | 0.0673 (8) | |
H14 | 0.7645 | 1.0629 | 0.1392 | 0.081* | |
C15 | 0.7794 (4) | 0.9999 (3) | 0.05856 (14) | 0.0727 (9) | |
H15 | 0.7523 | 1.0906 | 0.0417 | 0.087* | |
C16 | 0.8116 (4) | 0.8830 (3) | 0.02531 (12) | 0.0666 (8) | |
H16 | 0.8061 | 0.8942 | −0.0142 | 0.080* | |
C17 | 0.8520 (3) | 0.7485 (3) | 0.05001 (10) | 0.0504 (6) | |
H17 | 0.8724 | 0.6693 | 0.0269 | 0.060* | |
C18 | 1.0451 (3) | 0.3473 (3) | 0.09951 (10) | 0.0503 (6) | |
H18A | 0.9886 | 0.3552 | 0.0612 | 0.075* | |
H18B | 0.9809 | 0.2877 | 0.1222 | 0.075* | |
H18C | 1.1517 | 0.3029 | 0.0985 | 0.075* | |
C19 | 1.3263 (4) | 0.5493 (3) | 0.27297 (11) | 0.0783 (9) | |
H19A | 1.4432 | 0.5683 | 0.2799 | 0.117* | |
H19B | 1.3046 | 0.4508 | 0.2847 | 0.117* | |
H19C | 1.2686 | 0.6175 | 0.2945 | 0.117* | |
C20 | 1.3705 (4) | 0.7944 (3) | 0.09317 (13) | 0.0803 (10) | |
H20A | 1.4539 | 0.7445 | 0.0751 | 0.121* | |
H20B | 1.4218 | 0.8676 | 0.1190 | 0.121* | |
H20C | 1.2931 | 0.8408 | 0.0644 | 0.121* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0490 (13) | 0.0549 (13) | 0.0392 (12) | 0.0034 (11) | −0.0110 (9) | −0.0031 (10) |
N2 | 0.0448 (12) | 0.0524 (13) | 0.0499 (13) | −0.0048 (10) | 0.0035 (10) | −0.0005 (10) |
O1 | 0.0509 (10) | 0.0554 (11) | 0.0329 (9) | 0.0088 (8) | −0.0009 (7) | −0.0072 (7) |
O2 | 0.0666 (13) | 0.0819 (14) | 0.0730 (13) | −0.0225 (12) | −0.0044 (11) | −0.0256 (11) |
O3 | 0.0560 (12) | 0.0921 (14) | 0.0402 (11) | −0.0015 (10) | 0.0092 (8) | −0.0015 (9) |
C1 | 0.0403 (14) | 0.0433 (14) | 0.0290 (12) | 0.0050 (11) | 0.0004 (10) | −0.0041 (10) |
C2 | 0.0387 (13) | 0.0403 (13) | 0.0336 (12) | 0.0042 (11) | −0.0008 (10) | −0.0043 (10) |
C3 | 0.0467 (15) | 0.0395 (14) | 0.0402 (14) | 0.0043 (12) | −0.0011 (11) | −0.0030 (11) |
C4 | 0.0450 (15) | 0.0526 (17) | 0.0519 (16) | 0.0041 (13) | 0.0012 (13) | −0.0122 (13) |
C5 | 0.0377 (14) | 0.0522 (16) | 0.0414 (15) | 0.0069 (12) | 0.0024 (11) | −0.0021 (12) |
C6 | 0.0379 (13) | 0.0414 (14) | 0.0405 (14) | 0.0063 (11) | 0.0067 (11) | 0.0006 (11) |
C7 | 0.0573 (17) | 0.0665 (18) | 0.0442 (15) | −0.0029 (15) | 0.0119 (12) | 0.0020 (13) |
C8 | 0.0656 (19) | 0.070 (2) | 0.065 (2) | −0.0033 (16) | 0.0253 (16) | 0.0127 (15) |
C9 | 0.0438 (16) | 0.0573 (18) | 0.085 (2) | −0.0021 (14) | 0.0134 (15) | 0.0074 (16) |
C10 | 0.0402 (15) | 0.0623 (18) | 0.0680 (19) | −0.0026 (14) | −0.0062 (13) | 0.0037 (15) |
C11 | 0.0447 (15) | 0.0519 (16) | 0.0467 (15) | −0.0002 (13) | 0.0015 (12) | 0.0076 (12) |
C12 | 0.0324 (13) | 0.0391 (14) | 0.0434 (14) | 0.0010 (10) | 0.0027 (10) | −0.0035 (11) |
C13 | 0.0477 (15) | 0.0505 (16) | 0.0512 (15) | 0.0059 (13) | −0.0016 (12) | −0.0098 (13) |
C14 | 0.073 (2) | 0.0418 (16) | 0.083 (2) | 0.0119 (14) | −0.0031 (16) | −0.0150 (15) |
C15 | 0.087 (2) | 0.0434 (17) | 0.083 (2) | 0.0064 (15) | −0.0078 (18) | 0.0103 (16) |
C16 | 0.089 (2) | 0.0519 (18) | 0.0564 (17) | 0.0058 (16) | −0.0001 (15) | 0.0085 (14) |
C17 | 0.0587 (17) | 0.0438 (15) | 0.0483 (16) | 0.0068 (13) | 0.0059 (12) | 0.0010 (12) |
C18 | 0.0462 (15) | 0.0501 (15) | 0.0524 (15) | 0.0065 (12) | −0.0026 (12) | −0.0129 (12) |
C19 | 0.082 (2) | 0.095 (2) | 0.0493 (17) | −0.0024 (19) | −0.0221 (15) | 0.0001 (16) |
C20 | 0.078 (2) | 0.082 (2) | 0.082 (2) | −0.0240 (18) | 0.0150 (18) | 0.0105 (17) |
N1—C4 | 1.353 (3) | C9—H9 | 0.9300 |
N1—C3 | 1.412 (3) | C10—C11 | 1.373 (3) |
N1—C19 | 1.457 (3) | C10—H10 | 0.9300 |
N2—C5 | 1.377 (3) | C11—H11 | 0.9300 |
N2—C4 | 1.396 (3) | C12—C13 | 1.381 (3) |
N2—C20 | 1.460 (3) | C12—C17 | 1.383 (3) |
O1—C3 | 1.450 (3) | C13—C14 | 1.379 (4) |
O1—C1 | 1.452 (2) | C13—H13 | 0.9300 |
O2—C4 | 1.214 (3) | C14—C15 | 1.364 (4) |
O3—C5 | 1.214 (3) | C14—H14 | 0.9300 |
C1—C12 | 1.504 (3) | C15—C16 | 1.365 (4) |
C1—C6 | 1.521 (3) | C15—H15 | 0.9300 |
C1—C2 | 1.600 (3) | C16—C17 | 1.376 (3) |
C2—C5 | 1.497 (3) | C16—H16 | 0.9300 |
C2—C18 | 1.515 (3) | C17—H17 | 0.9300 |
C2—C3 | 1.523 (3) | C18—H18A | 0.9600 |
C3—H3 | 0.9800 | C18—H18B | 0.9600 |
C6—C7 | 1.376 (3) | C18—H18C | 0.9600 |
C6—C11 | 1.386 (3) | C19—H19A | 0.9600 |
C7—C8 | 1.375 (4) | C19—H19B | 0.9600 |
C7—H7 | 0.9300 | C19—H19C | 0.9600 |
C8—C9 | 1.366 (4) | C20—H20A | 0.9600 |
C8—H8 | 0.9300 | C20—H20B | 0.9600 |
C9—C10 | 1.373 (4) | C20—H20C | 0.9600 |
C4—N1—C3 | 121.2 (2) | C11—C10—C9 | 120.2 (3) |
C4—N1—C19 | 117.4 (2) | C11—C10—H10 | 119.9 |
C3—N1—C19 | 117.8 (2) | C9—C10—H10 | 119.9 |
C5—N2—C4 | 124.3 (2) | C10—C11—C6 | 120.9 (2) |
C5—N2—C20 | 117.6 (2) | C10—C11—H11 | 119.6 |
C4—N2—C20 | 116.6 (2) | C6—C11—H11 | 119.6 |
C3—O1—C1 | 92.41 (14) | C13—C12—C17 | 118.0 (2) |
O1—C1—C12 | 110.28 (17) | C13—C12—C1 | 119.0 (2) |
O1—C1—C6 | 110.74 (17) | C17—C12—C1 | 122.9 (2) |
C12—C1—C6 | 112.78 (18) | C14—C13—C12 | 120.9 (2) |
O1—C1—C2 | 89.20 (14) | C14—C13—H13 | 119.6 |
C12—C1—C2 | 119.28 (18) | C12—C13—H13 | 119.6 |
C6—C1—C2 | 112.08 (17) | C15—C14—C13 | 120.1 (3) |
C5—C2—C18 | 110.54 (19) | C15—C14—H14 | 119.9 |
C5—C2—C3 | 112.83 (19) | C13—C14—H14 | 119.9 |
C18—C2—C3 | 117.16 (19) | C14—C15—C16 | 119.9 (3) |
C5—C2—C1 | 112.63 (18) | C14—C15—H15 | 120.1 |
C18—C2—C1 | 117.30 (18) | C16—C15—H15 | 120.1 |
C3—C2—C1 | 84.20 (15) | C15—C16—C17 | 120.3 (3) |
N1—C3—O1 | 112.77 (18) | C15—C16—H16 | 119.8 |
N1—C3—C2 | 117.63 (19) | C17—C16—H16 | 119.8 |
O1—C3—C2 | 92.34 (15) | C16—C17—C12 | 120.7 (2) |
N1—C3—H3 | 110.9 | C16—C17—H17 | 119.6 |
O1—C3—H3 | 110.9 | C12—C17—H17 | 119.6 |
C2—C3—H3 | 110.9 | C2—C18—H18A | 109.5 |
O2—C4—N1 | 122.7 (2) | C2—C18—H18B | 109.5 |
O2—C4—N2 | 120.6 (3) | H18A—C18—H18B | 109.5 |
N1—C4—N2 | 116.6 (2) | C2—C18—H18C | 109.5 |
O3—C5—N2 | 120.4 (2) | H18A—C18—H18C | 109.5 |
O3—C5—C2 | 121.7 (2) | H18B—C18—H18C | 109.5 |
N2—C5—C2 | 117.8 (2) | N1—C19—H19A | 109.5 |
C7—C6—C11 | 118.2 (2) | N1—C19—H19B | 109.5 |
C7—C6—C1 | 120.6 (2) | H19A—C19—H19B | 109.5 |
C11—C6—C1 | 121.07 (19) | N1—C19—H19C | 109.5 |
C8—C7—C6 | 120.7 (2) | H19A—C19—H19C | 109.5 |
C8—C7—H7 | 119.7 | H19B—C19—H19C | 109.5 |
C6—C7—H7 | 119.7 | N2—C20—H20A | 109.5 |
C9—C8—C7 | 120.7 (3) | N2—C20—H20B | 109.5 |
C9—C8—H8 | 119.7 | H20A—C20—H20B | 109.5 |
C7—C8—H8 | 119.7 | N2—C20—H20C | 109.5 |
C8—C9—C10 | 119.4 (3) | H20A—C20—H20C | 109.5 |
C8—C9—H9 | 120.3 | H20B—C20—H20C | 109.5 |
C10—C9—H9 | 120.3 | ||
C3—O1—C1—C12 | −131.48 (18) | C20—N2—C5—C2 | −170.0 (2) |
C3—O1—C1—C6 | 102.98 (19) | C18—C2—C5—O3 | 37.6 (3) |
C3—O1—C1—C2 | −10.39 (16) | C3—C2—C5—O3 | 170.9 (2) |
O1—C1—C2—C5 | −102.41 (19) | C1—C2—C5—O3 | −95.8 (3) |
C12—C1—C2—C5 | 10.5 (3) | C18—C2—C5—N2 | −144.8 (2) |
C6—C1—C2—C5 | 145.47 (19) | C3—C2—C5—N2 | −11.4 (3) |
O1—C1—C2—C18 | 127.57 (19) | C1—C2—C5—N2 | 81.9 (2) |
C12—C1—C2—C18 | −119.5 (2) | O1—C1—C6—C7 | −6.9 (3) |
C6—C1—C2—C18 | 15.5 (3) | C12—C1—C6—C7 | −131.1 (2) |
O1—C1—C2—C3 | 9.93 (15) | C2—C1—C6—C7 | 91.0 (2) |
C12—C1—C2—C3 | 122.9 (2) | O1—C1—C6—C11 | 177.12 (19) |
C6—C1—C2—C3 | −102.19 (18) | C12—C1—C6—C11 | 53.0 (3) |
C4—N1—C3—O1 | −72.4 (3) | C2—C1—C6—C11 | −85.0 (2) |
C19—N1—C3—O1 | 85.8 (3) | C11—C6—C7—C8 | 0.7 (4) |
C4—N1—C3—C2 | 33.3 (3) | C1—C6—C7—C8 | −175.3 (2) |
C19—N1—C3—C2 | −168.6 (2) | C6—C7—C8—C9 | 0.3 (4) |
C1—O1—C3—N1 | 132.30 (19) | C7—C8—C9—C10 | −1.1 (4) |
C1—O1—C3—C2 | 10.93 (17) | C8—C9—C10—C11 | 0.7 (4) |
C5—C2—C3—N1 | −15.1 (3) | C9—C10—C11—C6 | 0.4 (4) |
C18—C2—C3—N1 | 115.0 (2) | C7—C6—C11—C10 | −1.1 (3) |
C1—C2—C3—N1 | −127.2 (2) | C1—C6—C11—C10 | 174.9 (2) |
C5—C2—C3—O1 | 102.19 (19) | O1—C1—C12—C13 | −27.7 (3) |
C18—C2—C3—O1 | −127.7 (2) | C6—C1—C12—C13 | 96.7 (2) |
C1—C2—C3—O1 | −9.95 (15) | C2—C1—C12—C13 | −128.7 (2) |
C3—N1—C4—O2 | 160.5 (2) | O1—C1—C12—C17 | 154.5 (2) |
C19—N1—C4—O2 | 2.3 (4) | C6—C1—C12—C17 | −81.1 (3) |
C3—N1—C4—N2 | −22.0 (3) | C2—C1—C12—C17 | 53.5 (3) |
C19—N1—C4—N2 | 179.8 (2) | C17—C12—C13—C14 | −0.8 (4) |
C5—N2—C4—O2 | 169.6 (2) | C1—C12—C13—C14 | −178.7 (2) |
C20—N2—C4—O2 | 3.8 (3) | C12—C13—C14—C15 | 0.0 (4) |
C5—N2—C4—N1 | −7.9 (3) | C13—C14—C15—C16 | 0.5 (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—O3 | 7.7 (3) | C13—C12—C17—C16 | 1.2 (4) |
C4—N2—C5—C2 | 24.4 (3) | C1—C12—C17—C16 | 179.0 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O2i | 0.98 | 2.53 | 3.431 (3) | 153 |
C7—H7···O1 | 0.93 | 2.37 | 2.745 (3) | 104 |
C8—H8···O1ii | 0.93 | 2.59 | 3.513 (3) | 171 |
C13—H13···O1 | 0.93 | 2.41 | 2.752 (3) | 101 |
C17—H17···O3 | 0.93 | 2.55 | 3.040 (3) | 113 |
C20—H20B···O2 | 0.96 | 2.29 | 2.682 (4) | 104 |
Symmetry codes: (i) −x+5/2, y−1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C20H20N2O3 |
Mr | 336.38 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 298 |
a, b, c (Å) | 8.1341 (7), 9.1004 (13), 23.485 (2) |
β (°) | 97.334 (2) |
V (Å3) | 1724.2 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.45 × 0.41 × 0.18 |
Data collection | |
Diffractometer | Bruker SMART diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.962, 0.984 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8774, 3039, 1818 |
Rint | 0.036 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.117, 1.01 |
No. of reflections | 3039 |
No. of parameters | 226 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.18 |
Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O2i | 0.98 | 2.53 | 3.431 (3) | 153 |
C7—H7···O1 | 0.93 | 2.37 | 2.745 (3) | 104 |
C8—H8···O1ii | 0.93 | 2.59 | 3.513 (3) | 171 |
C13—H13···O1 | 0.93 | 2.41 | 2.752 (3) | 101 |
C17—H17···O3 | 0.93 | 2.55 | 3.040 (3) | 113 |
C20—H20B···O2 | 0.96 | 2.29 | 2.682 (4) | 104 |
Symmetry codes: (i) −x+5/2, y−1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2. |
Acknowledgements
This work was supported by the Grants for Scientific Research of BSKY (grant No. XJ200712) from Anhui Medical University.
References
Hei, X. M., Song, Q. H., Tang, W. J., Wang, H. B. & Guo, Q. X. (2005). J. Org. Chem. 70, 2522–2527. Web of Science CrossRef PubMed CAS Google Scholar
Prakash, G., Fettinger, J. C. & Falvey, D. E. (1997). Acta Cryst. C53, 979–981. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siemens (1996). SMART and SAINT. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Google Scholar
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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.