Acta Cryst. (2007). E63, o3943 [ doi:10.1107/S1600536807035568 ]
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-5-Bromo-N-tert-butyl-2-methoxyphenylnitroneThe title compound, C12H16BrNO2, was synthesized in 95% yield by condensation of 5-bromo-2-methoxybenzaldehyde and N-tert-butyl-hydroxylamine acetate in the presence of triethylamine as the base and anhydrous magnesium sulfate as the dehydrating agent. The C=N bond leads to a plane containing all atoms of the side chain, excluding the three methyl groups; this plane makes a dihedral angle of 14.44 (3)° with the ring plane.
An oven-dried Schlenk flask was charged with 5-bromo-2-methoxybenzaldehyde (215 mg, 1.0 mmol), N-tert-butyl hydroxylamine acetate (298 mg, 2.0 mmol) and anhydrous magnesium sulfate (362 mg, 3.0 mmol) under argon. Triethylamine (350 µl, 253 mg, 2.5 mmol) was then added via syringe followed by anhydrous benzene (6 ml, distilled from sodium/benzophenone). After stirring at 363 K in a Schlenk flask for 15 d, the reaction mixture was filtered to remove the magnesium sulfate and the filtrate concentrated to dryness with a rotary evaporator. The crude mixture was purified by flash column chromatography on silica gel (60 230–400 mesh) using a 11:1 (v/v) dichloromethane/ethyl acetate solution as the eluent to give the title compound (yield; 270 mg, 95%, m.p. 372–373 K), as white solid. Crystals suitable for X-ray analysis were grown by slow solvent diffusion by layering hexane over a solution of the nitrone in dichloromethane. 1H-NMR (500 MHz, in CDCl3 at 25°C): δ 9.54 (1 H, d, J = 2.5 Hz), 7.95 (1 H, s), 7.36 (1H, dd, J = 2.5 and 8.5 Hz), 6.69 (1 H, d, J = 8.5 Hz), 3.80 (3H, s), 1.56 (9 H, s). 13 C-NMR (125 MHz, CDCl3): δ156.0, 133.3, 130.7, 123.0, 121.9, 113.3, 111.3, 71.4, 55.9, 28.3. Anal. Calcd for C12H16BrNO2: C, 50.37; H, 5.64; N, 4.89. Found: C, 50.34; H, 5.55; N 4.82.
H atoms were positioned geometrically with C—H = 0.93 and 0.96 Å for aromatic and methyl H atoms, respectively, and constrained to ride on their parent atoms, with Uiso(H) = xUeq(C), where x = 1.2 for aromatic H and x = 1.5 for methyl H atoms.
Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1997); software used to prepare material for publication: SHELXTL.
| C12H16BrNO2 | F000 = 584 |
| Mr = 286.17 | Dx = 1.508 Mg m−3 |
| Monoclinic, P21/c | Melting point = 372–373 K |
| Hall symbol: -P 2ybc | Mo Kα radiation λ = 0.71073 Å |
| a = 10.7519 (11) Å | Cell parameters from 637 reflections |
| b = 10.0159 (10) Å | θ = −14–14º |
| c = 11.8287 (12) Å | µ = 3.25 mm−1 |
| β = 98.426 (2)º | T = 298 (2) K |
| V = 1260.1 (2) Å3 | Plate, colorless |
| Z = 4 | 0.6 × 0.1 × 0.04 mm |
| Siemens SMART CCD PLATFORM diffractometer | 2221 independent reflections |
| Radiation source: fine-focus sealed tube | 1950 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.018 |
| Detector resolution: 0 pixels mm-1 | θmax = 25.0º |
| T = 293(2) K | θmin = 1.9º |
| ω scans | h = −12→12 |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2000) | k = −11→11 |
| Tmin = 0.600, Tmax = 0.880 | l = −14→13 |
| 9284 measured reflections |
| Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
| Least-squares matrix: full | H-atom parameters constrained |
| R[F2 > 2σ(F2)] = 0.028 | w = 1/[σ2(Fo2) + (0.0461P)2 + 0.6983P] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.081 | (Δ/σ)max = 0.001 |
| S = 1.00 | Δρmax = 0.54 e Å−3 |
| 2221 reflections | Δρmin = −0.55 e Å−3 |
| 150 parameters | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0048 (9) |
| Secondary atom site location: difference Fourier map |
| C12H16BrNO2 | V = 1260.1 (2) Å3 |
| Mr = 286.17 | Z = 4 |
| Monoclinic, P21/c | Mo Kα |
| a = 10.7519 (11) Å | µ = 3.25 mm−1 |
| b = 10.0159 (10) Å | T = 298 (2) K |
| c = 11.8287 (12) Å | 0.6 × 0.1 × 0.04 mm |
| β = 98.426 (2)º |
| Siemens SMART CCD PLATFORM diffractometer | 2221 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2000) | 1950 reflections with I > 2σ(I) |
| Tmin = 0.600, Tmax = 0.880 | Rint = 0.018 |
| 9284 measured reflections |
| R[F2 > 2σ(F2)] = 0.028 | 150 parameters |
| wR(F2) = 0.081 | H-atom parameters constrained |
| S = 1.00 | Δρmax = 0.54 e Å−3 |
| 2221 reflections | Δρmin = −0.55 e Å−3 |
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. |
| x | y | z | Uiso*/Ueq | ||
| Br1 | 0.63640 (2) | 1.08818 (3) | 0.11983 (3) | 0.06566 (15) | |
| O1 | 0.27617 (18) | 1.07684 (18) | 0.46435 (16) | 0.0588 (5) | |
| O2 | 0.20183 (18) | 0.8842 (2) | 0.08330 (15) | 0.0592 (5) | |
| N1 | 0.16209 (17) | 0.87311 (19) | 0.18066 (16) | 0.0397 (4) | |
| C1 | 0.5214 (2) | 1.0907 (2) | 0.2277 (2) | 0.0501 (6) | |
| C2 | 0.5503 (3) | 1.1622 (3) | 0.3274 (3) | 0.0592 (7) | |
| H2 | 0.6241 | 1.2118 | 0.3409 | 0.071* | |
| C3 | 0.4689 (3) | 1.1596 (3) | 0.4070 (3) | 0.0597 (7) | |
| H3 | 0.4877 | 1.2085 | 0.4742 | 0.072* | |
| C4 | 0.3592 (2) | 1.0853 (2) | 0.3883 (2) | 0.0484 (6) | |
| C5 | 0.3288 (2) | 1.0120 (2) | 0.2859 (2) | 0.0421 (5) | |
| C6 | 0.4117 (2) | 1.0173 (2) | 0.2052 (2) | 0.0455 (5) | |
| H6 | 0.3929 | 0.9715 | 0.1364 | 0.055* | |
| C7 | 0.3052 (3) | 1.1467 (3) | 0.5702 (2) | 0.0667 (8) | |
| H71 | 0.3852 | 1.1173 | 0.6090 | 0.100* | |
| H72 | 0.2414 | 1.1290 | 0.6172 | 0.100* | |
| H73 | 0.3085 | 1.2409 | 0.5557 | 0.100* | |
| C8 | 0.2159 (2) | 0.9307 (2) | 0.2740 (2) | 0.0420 (5) | |
| H8 | 0.1783 | 0.9185 | 0.3392 | 0.050* | |
| C9 | 0.0438 (2) | 0.7883 (2) | 0.17651 (19) | 0.0413 (5) | |
| C10 | 0.0712 (3) | 0.6562 (3) | 0.1223 (2) | 0.0539 (6) | |
| H101 | 0.1031 | 0.6726 | 0.0519 | 0.081* | |
| H102 | −0.0048 | 0.6048 | 0.1072 | 0.081* | |
| H103 | 0.1326 | 0.6076 | 0.1734 | 0.081* | |
| C11 | −0.0599 (2) | 0.8639 (3) | 0.1020 (3) | 0.0603 (7) | |
| H111 | −0.0713 | 0.9495 | 0.1356 | 0.090* | |
| H112 | −0.1368 | 0.8140 | 0.0962 | 0.090* | |
| H113 | −0.0371 | 0.8760 | 0.0272 | 0.090* | |
| C12 | 0.0096 (3) | 0.7633 (3) | 0.2947 (2) | 0.0548 (6) | |
| H121 | 0.0803 | 0.7249 | 0.3427 | 0.082* | |
| H122 | −0.0604 | 0.7029 | 0.2891 | 0.082* | |
| H123 | −0.0127 | 0.8462 | 0.3271 | 0.082* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Br1 | 0.03918 (18) | 0.0856 (3) | 0.0715 (2) | −0.01188 (13) | 0.00567 (13) | 0.01389 (14) |
| O1 | 0.0474 (11) | 0.0666 (12) | 0.0622 (11) | −0.0067 (8) | 0.0068 (9) | −0.0208 (9) |
| O2 | 0.0464 (10) | 0.0871 (13) | 0.0445 (10) | −0.0183 (9) | 0.0076 (8) | 0.0022 (9) |
| N1 | 0.0325 (10) | 0.0430 (10) | 0.0430 (10) | −0.0023 (8) | 0.0036 (8) | 0.0011 (8) |
| C1 | 0.0358 (13) | 0.0470 (14) | 0.0656 (16) | −0.0030 (10) | 0.0013 (11) | 0.0114 (11) |
| C2 | 0.0394 (14) | 0.0499 (15) | 0.085 (2) | −0.0124 (11) | −0.0010 (13) | −0.0011 (14) |
| C3 | 0.0487 (15) | 0.0535 (15) | 0.0732 (18) | −0.0087 (12) | −0.0039 (13) | −0.0147 (13) |
| C4 | 0.0385 (14) | 0.0432 (13) | 0.0612 (15) | 0.0008 (10) | 0.0001 (11) | −0.0041 (11) |
| C5 | 0.0350 (12) | 0.0372 (11) | 0.0522 (13) | 0.0003 (9) | −0.0001 (10) | 0.0014 (10) |
| C6 | 0.0374 (12) | 0.0436 (12) | 0.0531 (13) | −0.0015 (10) | −0.0013 (10) | 0.0045 (10) |
| C7 | 0.0638 (19) | 0.0736 (18) | 0.0598 (17) | 0.0012 (15) | −0.0007 (14) | −0.0184 (15) |
| C8 | 0.0354 (12) | 0.0420 (12) | 0.0482 (13) | −0.0031 (9) | 0.0050 (10) | −0.0026 (10) |
| C9 | 0.0336 (11) | 0.0404 (12) | 0.0492 (12) | −0.0059 (9) | 0.0038 (9) | −0.0009 (10) |
| C10 | 0.0563 (16) | 0.0473 (14) | 0.0578 (15) | −0.0035 (12) | 0.0067 (12) | −0.0081 (12) |
| C11 | 0.0372 (14) | 0.0570 (15) | 0.0822 (19) | −0.0030 (12) | −0.0064 (13) | 0.0019 (14) |
| C12 | 0.0503 (15) | 0.0586 (15) | 0.0585 (15) | −0.0161 (12) | 0.0182 (12) | −0.0092 (12) |
| Br1—C1 | 1.903 (3) | C7—H71 | 0.9600 |
| O1—C4 | 1.360 (3) | C7—H72 | 0.9600 |
| O1—C7 | 1.429 (3) | C7—H73 | 0.9600 |
| O2—N1 | 1.290 (3) | C8—H8 | 0.9300 |
| N1—C8 | 1.304 (3) | C9—C12 | 1.517 (3) |
| N1—C9 | 1.525 (3) | C9—C10 | 1.518 (3) |
| C1—C2 | 1.376 (4) | C9—C11 | 1.518 (3) |
| C1—C6 | 1.382 (3) | C10—H101 | 0.9600 |
| C2—C3 | 1.377 (4) | C10—H102 | 0.9600 |
| C2—H2 | 0.9300 | C10—H103 | 0.9600 |
| C3—C4 | 1.384 (4) | C11—H111 | 0.9600 |
| C3—H3 | 0.9300 | C11—H112 | 0.9600 |
| C4—C5 | 1.413 (3) | C11—H113 | 0.9600 |
| C5—C6 | 1.399 (3) | C12—H121 | 0.9600 |
| C5—C8 | 1.452 (3) | C12—H122 | 0.9600 |
| C6—H6 | 0.9300 | C12—H123 | 0.9600 |
| C4—O1—C7 | 118.0 (2) | N1—C8—C5 | 126.3 (2) |
| O2—N1—C8 | 123.66 (19) | N1—C8—H8 | 116.9 |
| O2—N1—C9 | 113.76 (17) | C5—C8—H8 | 116.9 |
| C8—N1—C9 | 122.57 (19) | C12—C9—C10 | 109.5 (2) |
| C2—C1—C6 | 121.4 (3) | C12—C9—C11 | 111.1 (2) |
| C2—C1—Br1 | 119.61 (19) | C10—C9—C11 | 111.2 (2) |
| C6—C1—Br1 | 118.9 (2) | C12—C9—N1 | 112.07 (18) |
| C1—C2—C3 | 119.3 (2) | C10—C9—N1 | 106.65 (19) |
| C1—C2—H2 | 120.3 | C11—C9—N1 | 106.18 (18) |
| C3—C2—H2 | 120.3 | C9—C10—H101 | 109.5 |
| C2—C3—C4 | 120.9 (3) | C9—C10—H102 | 109.5 |
| C2—C3—H3 | 119.6 | H101—C10—H102 | 109.5 |
| C4—C3—H3 | 119.6 | C9—C10—H103 | 109.5 |
| O1—C4—C3 | 123.7 (2) | H101—C10—H103 | 109.5 |
| O1—C4—C5 | 116.3 (2) | H102—C10—H103 | 109.5 |
| C3—C4—C5 | 120.0 (2) | C9—C11—H111 | 109.5 |
| C6—C5—C4 | 118.4 (2) | C9—C11—H112 | 109.5 |
| C6—C5—C8 | 124.2 (2) | H111—C11—H112 | 109.5 |
| C4—C5—C8 | 117.4 (2) | C9—C11—H113 | 109.5 |
| C1—C6—C5 | 120.0 (2) | H111—C11—H113 | 109.5 |
| C1—C6—H6 | 120.0 | H112—C11—H113 | 109.5 |
| C5—C6—H6 | 120.0 | C9—C12—H121 | 109.5 |
| O1—C7—H71 | 109.5 | C9—C12—H122 | 109.5 |
| O1—C7—H72 | 109.5 | H121—C12—H122 | 109.5 |
| H71—C7—H72 | 109.5 | C9—C12—H123 | 109.5 |
| O1—C7—H73 | 109.5 | H121—C12—H123 | 109.5 |
| H71—C7—H73 | 109.5 | H122—C12—H123 | 109.5 |
| H72—C7—H73 | 109.5 |
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![[Figure 1]](./hk2299fig1thm.gif)
Nitrones are versatile organic compounds widely used as 1,3-dipoles in cycloadditions (Merino & Padwa, 2004; Torsell, 1988), spin trapping agents in free radical chemistry (Janzen, 1971; Usuki et al., 2006) and also in biological studies (Zhang et al., 2000). Recently they have also been employed as therapeutics in age-related diseases (Floyd, 2006). Nitrones undergo many reactions, such as the Behrend Rearrangement, nitrone-oxime O-ether rearrangement, and thermolytic alkene elimination (Torsell, 1988). While the most conventional procedures for the preparation of nitrones have been the condensation of N-monosubstituted hydroxylamines with carbonyl compounds and the N-alkylation of oximes (Torsell, 1988), a newly reported high yielding and chemoselective procedure for the conversion of imines to nitrones using catalytic amounts of methyltrioxorhenium represents a breakthrough in nitrone synthesis (Soldaini et al., 2007). We have recently shown that nitrones derived from aromatic aldehydes can be used as convenient precursors to carbocyclic carbene ligands for the synthesis of novel and catalytically useful Pd compounds (Yao et al., 2007). The formation of nitrone-based Pd complexes involves the selective C—H activation of the aromatic ring via orthopalladation directed by the oxygen atom on the nitrone moiety. It can be expected that the stereochemistry around the C=N of the nitrone group would have a pronounced effect in formation of the Ccarbene—Pd bond. For this purpose, we have synthesized the title compound, (I), and reported herein its crystal structure.
In the molecule of the title compound, (I), (Fig. 1) the bond lengths and angles are generally within normal ranges (Allen et al., 1987). The C8=N1 double bond leads to a plane containing C9, O2, N1, C8 and C5 atoms, and the dihedral angle between (C1—C6) ring and the plane of (N1/O2/C5/C8/C) is 14.44 (3)°.