Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113000681/fa3302sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113000681/fa3302Isup2.hkl | |
Chemdraw file https://doi.org/10.1107/S0108270113000681/fa3302Isup3.cdx | |
Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270113000681/fa3302Isup4.cml |
CCDC reference: 925774
For related literature, see: Cradwick (1976); Groziak & Robinson (2002); Groziak et al. (1994, 1997); Hauser & Renfrow (1939); Robinson & Groziak (1999); Robinson et al. (1996, 1998); Scouten et al. (1994).
(2-Ethoxycarbonylphenyl)boronic acid (Aldrich) was condensed with excess NH2OH in aqueous KOH according to a procedure reported for the preparation of benzohydroxamic acid from ethyl benzoate (Hauser & Renfrow, 1939). The solid potassium hydroxamate salt obtained in the first step was isolated as a white solid, and the solid was dissolved in H2O and passed through a column of Dowex 50WX8 cation exchange resin (H+ form). Slow evaporation of the eluate gave the title compound (iield 83%, from the K+ salt) as colorless crystals (m.p. 482–484 K, H2O). 1H NMR [(CD3)2SO]: δ 11.82 (bs, exchanges, 1H, OH), 9.49 (bs, exchanges, 1H, NH), 8.09 (d, J = 7.6 Hz, 1H, ArH), 7.98 (d, J = 7.1 Hz, 1H, ArH), 7.81 (pseudo-t, 1H, ArH), 7.75 (pseudo-t, 1H, ArH). 13C NMR [(CD3)2SO]: δ 161.2 (C═O), 135.1, 132.8, 132.7, 132.3, 128.0 (br, C—B), 126.3. FT–IR, ν (cm-1): 3314 (br, OH), 1625 (C═O), 1409, 1292, 1235, 1125. UV λ max (CH3OH): 231, 273 nm.
H atoms bonded to C atoms were refined as riding on their parent atoms, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C). H atoms bonded to N and O atoms were located in a difference Fourier map and were subsequently freely refined with no restraints.
Data collection: APEX2 (Bruker, 2011); cell refinement: SAINT (Bruker, 2011); data reduction: SAINT (Bruker, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
C7H6BNO3 | F(000) = 336 |
Mr = 162.94 | Dx = 1.537 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 8670 reflections |
a = 9.0848 (3) Å | θ = 3.3–32.9° |
b = 6.2043 (2) Å | µ = 0.12 mm−1 |
c = 13.1207 (5) Å | T = 90 K |
β = 107.792 (2)° | Block, colourless |
V = 704.17 (4) Å3 | 0.50 × 0.33 × 0.20 mm |
Z = 4 |
Bruker APEXII diffractometer | 2564 independent reflections |
Radiation source: fine-focus sealed tube | 2420 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.012 |
Detector resolution: 8.3 pixels mm-1 | θmax = 33.1°, θmin = 2.4° |
ω scans | h = −13→13 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −9→9 |
Tmin = 0.943, Tmax = 0.977 | l = −20→20 |
11658 measured reflections |
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)] = 0.034 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.103 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0626P)2 + 0.1884P] where P = (Fo2 + 2Fc2)/3 |
2564 reflections | (Δ/σ)max = 0.001 |
117 parameters | Δρmax = 0.54 e Å−3 |
0 restraints | Δρmin = −0.24 e Å−3 |
C7H6BNO3 | V = 704.17 (4) Å3 |
Mr = 162.94 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 9.0848 (3) Å | µ = 0.12 mm−1 |
b = 6.2043 (2) Å | T = 90 K |
c = 13.1207 (5) Å | 0.50 × 0.33 × 0.20 mm |
β = 107.792 (2)° |
Bruker APEXII diffractometer | 2564 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2420 reflections with I > 2σ(I) |
Tmin = 0.943, Tmax = 0.977 | Rint = 0.012 |
11658 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | 0 restraints |
wR(F2) = 0.103 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.54 e Å−3 |
2564 reflections | Δρmin = −0.24 e Å−3 |
117 parameters |
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 | ||
O1 | 0.40195 (6) | −0.00533 (8) | 0.20721 (4) | 0.01483 (12) | |
O2 | 0.40143 (6) | −0.24104 (8) | 0.45339 (4) | 0.01368 (12) | |
O3 | 0.26801 (6) | −0.16815 (9) | 0.57746 (4) | 0.01599 (12) | |
H3 | 0.316 (2) | −0.283 (3) | 0.6146 (14) | 0.049 (4)* | |
N1 | 0.42848 (7) | −0.19124 (10) | 0.35710 (5) | 0.01385 (13) | |
H1 | 0.4867 (16) | −0.292 (2) | 0.3376 (11) | 0.030 (3)* | |
C1 | 0.22797 (7) | 0.08701 (11) | 0.41957 (5) | 0.01179 (13) | |
C2 | 0.12594 (8) | 0.22893 (12) | 0.44704 (5) | 0.01483 (14) | |
H2 | 0.0931 | 0.1998 | 0.5078 | 0.018* | |
C3 | 0.07270 (9) | 0.41218 (12) | 0.38565 (6) | 0.01623 (14) | |
H3A | 0.0026 | 0.5067 | 0.4042 | 0.019* | |
C4 | 0.12176 (8) | 0.45789 (12) | 0.29689 (6) | 0.01533 (14) | |
H4 | 0.0870 | 0.5853 | 0.2566 | 0.018* | |
C5 | 0.22112 (8) | 0.31811 (11) | 0.26719 (5) | 0.01364 (13) | |
H5 | 0.2536 | 0.3480 | 0.2063 | 0.016* | |
C6 | 0.27254 (7) | 0.13246 (11) | 0.32847 (5) | 0.01141 (13) | |
C7 | 0.37126 (7) | −0.02250 (11) | 0.29437 (5) | 0.01168 (13) | |
B1 | 0.29826 (9) | −0.11392 (12) | 0.48663 (6) | 0.01219 (14) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0210 (2) | 0.0145 (2) | 0.0122 (2) | −0.00363 (18) | 0.00992 (18) | −0.00168 (16) |
O2 | 0.0180 (2) | 0.0140 (2) | 0.0112 (2) | 0.00282 (17) | 0.00770 (18) | 0.00227 (16) |
O3 | 0.0221 (3) | 0.0160 (2) | 0.0123 (2) | 0.00440 (19) | 0.00883 (19) | 0.00346 (17) |
N1 | 0.0184 (3) | 0.0133 (3) | 0.0131 (3) | 0.0023 (2) | 0.0096 (2) | 0.00100 (18) |
C1 | 0.0141 (3) | 0.0123 (3) | 0.0094 (3) | 0.0010 (2) | 0.0042 (2) | −0.00001 (19) |
C2 | 0.0183 (3) | 0.0156 (3) | 0.0116 (3) | 0.0035 (2) | 0.0061 (2) | −0.0001 (2) |
C3 | 0.0193 (3) | 0.0147 (3) | 0.0146 (3) | 0.0043 (2) | 0.0051 (2) | −0.0005 (2) |
C4 | 0.0178 (3) | 0.0124 (3) | 0.0143 (3) | 0.0011 (2) | 0.0028 (2) | 0.0011 (2) |
C5 | 0.0162 (3) | 0.0128 (3) | 0.0115 (3) | −0.0011 (2) | 0.0036 (2) | 0.0012 (2) |
C6 | 0.0131 (3) | 0.0115 (3) | 0.0099 (3) | −0.0007 (2) | 0.0039 (2) | −0.00071 (19) |
C7 | 0.0138 (3) | 0.0116 (3) | 0.0107 (3) | −0.0024 (2) | 0.0053 (2) | −0.00133 (19) |
B1 | 0.0146 (3) | 0.0126 (3) | 0.0103 (3) | 0.0006 (2) | 0.0050 (2) | 0.0001 (2) |
O1—C7 | 1.2616 (8) | C2—C3 | 1.3918 (10) |
O2—B1 | 1.3930 (9) | C2—H2 | 0.9500 |
O2—N1 | 1.3935 (7) | C3—C4 | 1.3974 (10) |
O3—B1 | 1.3449 (8) | C3—H3A | 0.9500 |
O3—H3 | 0.898 (18) | C4—C5 | 1.3906 (10) |
N1—C7 | 1.3350 (9) | C4—H4 | 0.9500 |
N1—H1 | 0.905 (15) | C5—C6 | 1.4008 (9) |
C1—C6 | 1.4029 (9) | C5—H5 | 0.9500 |
C1—C2 | 1.4031 (9) | C6—C7 | 1.4745 (9) |
C1—B1 | 1.5468 (10) | ||
B1—O2—N1 | 118.70 (5) | C5—C4—H4 | 119.8 |
B1—O3—H3 | 118.9 (11) | C3—C4—H4 | 119.8 |
C7—N1—O2 | 126.12 (6) | C4—C5—C6 | 118.89 (6) |
C7—N1—H1 | 121.2 (9) | C4—C5—H5 | 120.6 |
O2—N1—H1 | 112.6 (9) | C6—C5—H5 | 120.6 |
C6—C1—C2 | 118.56 (6) | C5—C6—C1 | 121.46 (6) |
C6—C1—B1 | 118.05 (6) | C5—C6—C7 | 119.28 (6) |
C2—C1—B1 | 123.37 (6) | C1—C6—C7 | 119.22 (6) |
C3—C2—C1 | 120.27 (6) | O1—C7—N1 | 118.21 (6) |
C3—C2—H2 | 119.9 | O1—C7—C6 | 122.92 (6) |
C1—C2—H2 | 119.9 | N1—C7—C6 | 118.85 (6) |
C2—C3—C4 | 120.34 (6) | O3—B1—O2 | 118.36 (6) |
C2—C3—H3A | 119.8 | O3—B1—C1 | 123.02 (6) |
C4—C3—H3A | 119.8 | O2—B1—C1 | 118.59 (6) |
C5—C4—C3 | 120.44 (6) | ||
B1—O2—N1—C7 | 4.21 (10) | O2—N1—C7—O1 | −177.11 (6) |
C6—C1—C2—C3 | −0.99 (10) | O2—N1—C7—C6 | 1.54 (10) |
B1—C1—C2—C3 | 177.02 (7) | C5—C6—C7—O1 | −5.99 (10) |
C1—C2—C3—C4 | −0.77 (11) | C1—C6—C7—O1 | 171.87 (6) |
C2—C3—C4—C5 | 1.68 (11) | C5—C6—C7—N1 | 175.42 (6) |
C3—C4—C5—C6 | −0.78 (10) | C1—C6—C7—N1 | −6.71 (9) |
C4—C5—C6—C1 | −1.02 (10) | N1—O2—B1—O3 | 177.37 (6) |
C4—C5—C6—C7 | 176.79 (6) | N1—O2—B1—C1 | −4.60 (9) |
C2—C1—C6—C5 | 1.90 (10) | C6—C1—B1—O3 | 177.52 (6) |
B1—C1—C6—C5 | −176.22 (6) | C2—C1—B1—O3 | −0.50 (11) |
C2—C1—C6—C7 | −175.92 (6) | C6—C1—B1—O2 | −0.41 (10) |
B1—C1—C6—C7 | 5.97 (9) | C2—C1—B1—O2 | −178.43 (6) |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O1i | 0.898 (18) | 1.797 (18) | 2.6864 (7) | 170.4 (16) |
N1—H1···O1ii | 0.905 (15) | 1.866 (15) | 2.7707 (8) | 177.2 (13) |
Symmetry codes: (i) x, −y−1/2, z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C7H6BNO3 |
Mr | 162.94 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 90 |
a, b, c (Å) | 9.0848 (3), 6.2043 (2), 13.1207 (5) |
β (°) | 107.792 (2) |
V (Å3) | 704.17 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.50 × 0.33 × 0.20 |
Data collection | |
Diffractometer | Bruker APEXII diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.943, 0.977 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11658, 2564, 2420 |
Rint | 0.012 |
(sin θ/λ)max (Å−1) | 0.768 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.103, 1.04 |
No. of reflections | 2564 |
No. of parameters | 117 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.54, −0.24 |
Computer programs: APEX2 (Bruker, 2011), SAINT (Bruker, 2011), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP in SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O1i | 0.898 (18) | 1.797 (18) | 2.6864 (7) | 170.4 (16) |
N1—H1···O1ii | 0.905 (15) | 1.866 (15) | 2.7707 (8) | 177.2 (13) |
Symmetry codes: (i) x, −y−1/2, z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
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The title compound, (Ia), was obtained by the condensation of (2-ethoxycarbonylphenyl)boronic acid and hydroxylamine. Based on previous work, we knew that the arylboronic acid and ortho-hydroxamic acid substituents had many possible modes of interaction, as summarized in Scheme 1. They could dehydrate to form a planar six-membered B—O heterocycle (Groziak et al., 1997; Robinson et al., 1998) existing in one of two prototropic forms, viz. (Ia) and (Ib). They could dehydrate to a five-membered boron B—N heterocycle, (II), or a B—O heterocycle in the form of either the (E) or (Z) oxime, viz. (IIIa) and (IIIb). They could interact by N···B chelation, (IV) (Groziak & Robinson, 2002), or form a covalent chelate (Groziak et al., 1994), or perhaps form a planar intramolecular hydrogen bond, (V) (Scouten et al., 1994; Robinson & Groziak, 1999). Alternatively, the boronic acid could dehydratively trimerize and interact with two hydroxamic acid groups to form an internally chelated boroxine (Robinson et al., 1996). Our results show that the boronic acid group has dehydratively condensed with the ortho-hydroxamic acid group to form a planar six-membered boron heterocycle ring, viz. (Ia).
In (Ia) (Fig. 1), the bicyclic ring system is essentially planar, with a mean deviation of 0.041 (1) Å from the least-squares plane defined by the ten constituent atoms. The cyclized hydroxamic acid group is clearly in a lactam rather than a lactim form. The heterocyclic periphery of (Ia) may be compared to those of the previously prepared (VI), (VII), and (VIII) (see Scheme 2) (Groziak et al. 1997; Robinson et al. 1998). The length of the newly formed B1—O2 bond in (Ia) [1.3930 (9) Å] compares favorably to that of the analogous bond in (VI) [1.388 (6) Å]. On the other hand, the O2—N1 bond length in (Ia) [1.3935 (7) Å] is shorter than that in (VI) [1.419 (6) Å]. The exocyclic B—O bond length in oxazaborine (VI) is 1.350 (6) Å, similar to the bond length of 1.3449 (8) Å in (Ia). Somewhat longer B—O distances (ca 1.37 Å) occur in diazaborines (VII) and (VIII).
The crystal structure of (Ia) is characterized by intermolecular B—O—H···O═C and N—H···O═C hydrogen bonding (Table 1). The intermolecular hydrogen-bonding scheme features a bifurcated interaction to atom O1 and an R42(14) graph set, as shown in Fig. 2. The crystal packing places the centroid of the 6:6 ring junction in line with the center of the hydrogen-bonded ring at a distance of 3.384 (1) Å, as shown in Fig. 3.
The molecule of (Ia) is a true B–O for C═N replacement analogue of 4-hydroxyphthalazin-1(2H)-one, (IX) (see Scheme 3), the ambident lactam/lactim form of 2,3-dihydrophthalazine-1,4-dione, but to our knowledge this structure has not been determined previously by crystallographic analysis. Instead, the closest nitrogen heterocycle reference compound appears to be 6-hydroxypyridazin-3(2H)-one, (X), the ambident lactam/lactim form of maleic hydrazide (Cradwick, 1976).