supplementary materials


fj2337 scheme

Acta Cryst. (2010). E66, o2646    [ doi:10.1107/S1600536810037864 ]

[2,2'-Iminodiethanolato(2-)-[kappa]3O,N,O'][4-(methoxycarbonylmethyl)phenyl]boron

A. L. Zein, L. N. Dawe and P. E. Georghiou

Abstract top

The title compound, C13H18BNO4, was readily obtained from the reaction of methyl 4-boronobenzene acetate with ethanolamine. A combination of intermolecular N-H...O hydrogen bonds and C-H...[pi] interactions leads to the pairwise association of molecules.

Comment top

Boron is known to be an important trace element in higher plants (Warrington, 1923) and boron-containing compounds have been shown to have a range of diverse biological acvtivities (Jabbour et al., 2004). The use of boron-containing reagents is also widespread in synthetic chemistry and this is due mainly to the pioneering work of H. C. Brown and coworkers and Suzuki and his coworkers (Miyaura & Suzuki, 1995). Corey, Bakshi and Shibata (Corey et al., 1987) discovered that a chrial oxazaborolidine ("CBS" reagent) which contains both boron-nitrogen and boron-oxygen bonds was capable of effecting enantioselective reduction of prochiral ketones, imines, and oximes to produce chiral alcohols, amines, and amino alcohols in excellent yields and ee's. Corey's group has also shown that chiral oxazaborolidine-aluminium bromide complexes (Liu et al. 2007) are also effective catalysts for enantioselective Diels-Alder reactions. In principle, oxazaborolidines are derived from reactions of a boronic acid and aminoalcohols and a less well known application of oxazaborolidines is to facilitate the conversion of a pinacolatoborane, by mild acid-catalysis (Jung & Lazarova, 1999), to the corresponding boronic acid, a key step for cupric acetate promoted coupling of an arylboronic acids with phenols (Chan et al., 1998; Evans et al., 1998; Lam et al. 1998).

There has been only one reported X-ray crystallographic study of the structure of a diethanolamine ester of a phenylboronic acid (1) (Rettig & Trotter, 1975). This compound which was named as B-phenyl-diptychboroxazolidine (alternative names: Tetrahydro-[1,3,2]oxaza-borol[2,3-b][1,3,2]oxazaborole; [[2,2'-(Imino-kN)bis[ethanolato-kO]](2-)]phenylboron) was measured on a diffractometer with Cu Ka radiation and it was revealed to be non-centrosymmetric and in the P21 space group. The absolute configuration of the enatiomorphic crystal was determined in this study. In connection with our own work (Wang & Georghiou, 2002), crystals of (2), the corresponding diethanolamine ester of the 4-boronic acid derivative of methyl phenylacetate, were obtained and the structure of the molecule is reported here.

Methyl p-[[2,2'-iminobis[ethanolato]](2-)-N,O,O']phenylacetateboron (2; Figure 1) crystallized in the non-centrosymmetric space group P212121, however, data collection was performed using molybdenum radiation, and the absolute configuration could not be determined due to the lack of an atom with significant anomalous dispersion. Intermolecular hydrogen bonding between N1—H1···O2i (N1···O2i = 2.921 (2) Å) and C—H···π interactions between C10—H10B···Cg3ii (C10···Cg3ii= 3.618 (2); where Cg3 is the centroid of C1—C6) leads to the pair-wise association of molecules (Figure 2). These molecular associates are related via the twofold screw axes in the crystal structure (viewed perpendicular to the b axis in Figure 3).

Related literature top

For background to the biological importance of boron, see: Warrington (1923); Jabbour et al. (2004). For the use of boron-containing reagents in synthetic chemistry, see: Miyaura et al. (1995); Corey et al. (1987); Liu et al. (2007) ;Jung et al. (1999); Chan et al. (1998); Evans et al. (1998); Lam et al. (1998). For related structures, see: Rettig & Trotter (1975); Wang & Georghiou (2002).

Experimental top

To a solution of PdCl2(dppf) (160 mg, 0.18 mmol) in dioxane (24 ml) was added methyl 4-(trifluoroacetoxyacetate (1.58 g, 5.93 mmol), Et3N (2.49 ml, 17.8 mmol) and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.30 ml, 8.9 mmol). After stirring for 20 h at 100 oC, the reaction mixture was extracted with benzene. The extract was purified by flash column chromatography (silica gel, 10%EtOAc in hexanes) to afford the arylboronate (1.47 g, 90%) 1HNMR (500 MHz, CDCl3) 1.34 (s, 12H), 3.64 (s, 2H), 3.67(s, 3H), 7.27(d, J=10 Hz, 2H), 7.77(d, J=10 Hz, 2H). To a solution of the arylboronate (1.47 g, 5.3 mmol) in diethylether (53 ml) was added diethanolamine (0.6 ml, 5.8 mmol) in 2-propanol (10 ml). The resulting mixture was stirred at ambient temperature for 72 h, the reaction mixture was then filtered and the solid was washed with diethyl ether to give cyclic aminoarylboronate (1.08 g, 77%) as a colorless powder. Crystals suitable for X-ray diffraction analysis were obtained by crystallization from ethyl acetate solution. 1H NMR (500 MHz, CDCl3) 2.49–2.51(m, 2H), 2.96–3.03(m, 2H), 3.58(s, 2H), 3.63(s, 3H), 3.70–3.72(m, 2H), 3.79–3.74(m, 2H), 5.83(s, 1H), 7.14(d, J=7.5 Hz, 2H), 7.43(d, J=7.5 Hz, 2H); 13C NMR 41.0, 51.1, 51.8, 63.2, 128.3, 132.7, 132.8, 172.6.

Refinement top

H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained distances and with Uiso(H) values set to either 1.2Ueq or 1.5Ueq of the attached atom. They were refined on a riding model. All non-hydrogen atoms were refined anisotropically. This crystal was a weak anomalous scatterer collected with MoKa radiation, therefore, Friedel mates were merged (MERG 4) and absolute configuration was not determined.

Computing details top

Data collection: CrystalClear (Rigaku, 2002); cell refinement: CrystalClear (Rigaku, 2002); data reduction: CrystalClear (Rigaku, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The molecular structure of (2), with atom labels and 50% probability displacement ellipsoids for non-H atoms.
[Figure 2] Fig. 2. Intermolecular hydrogen bonds (long dashes) and C—H···π interactions (short dashes) between two associated molecules.
[Figure 3] Fig. 3. Unit cell viewed perpendicular to the b axis, showing the pair-wise ordering of molecules in the crystal lattice. (Cell axes: a = red, b = green, c = blue)
[2,2'-Iminodiethanolato(2-)-κ3O,N,O'][4- (methoxycarbonylmethyl)phenyl]boron top
Crystal data top
C13H18BNO4Dx = 1.345 Mg m3
Mr = 263.10Melting point = 452–453 K
Orthorhombic, P212121Mo Kα radiation, λ = 0.71075 Å
Hall symbol: P 2ac 2abCell parameters from 5108 reflections
a = 8.3776 (11) Åθ = 2.6–30.6°
b = 8.9269 (11) ŵ = 0.10 mm1
c = 17.369 (2) ÅT = 153 K
V = 1299.0 (3) Å3Platelet, colorless
Z = 40.30 × 0.09 × 0.06 mm
F(000) = 560
Data collection top
Rigaku Saturn
diffractometer
1725 independent reflections
Radiation source: fine-focus sealed tube1707 reflections with I > 2σ(I)
graphite - Rigaku SHINERint = 0.037
Detector resolution: 14.63 pixels mm-1θmax = 27.5°, θmin = 2.6°
ω scansh = 1010
Absorption correction: numerical
(NUMABS; Higashi, 1999)
k = 1111
Tmin = 0.985, Tmax = 0.997l = 2222
16363 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.043Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.112H-atom parameters constrained
S = 1.17 w = 1/[σ2(Fo2) + (0.0529P)2 + 0.4126P]
where P = (Fo2 + 2Fc2)/3
1725 reflections(Δ/σ)max < 0.001
173 parametersΔρmax = 0.20 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C13H18BNO4V = 1299.0 (3) Å3
Mr = 263.10Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 8.3776 (11) ŵ = 0.10 mm1
b = 8.9269 (11) ÅT = 153 K
c = 17.369 (2) Å0.30 × 0.09 × 0.06 mm
Data collection top
Rigaku Saturn
diffractometer
1725 independent reflections
Absorption correction: numerical
(NUMABS; Higashi, 1999)
1707 reflections with I > 2σ(I)
Tmin = 0.985, Tmax = 0.997Rint = 0.037
16363 measured reflectionsθmax = 27.5°
Refinement top
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.112Δρmax = 0.20 e Å3
S = 1.17Δρmin = 0.22 e Å3
1725 reflectionsAbsolute structure: ?
173 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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.

The crystal was a weak anomalous scatterer collected with Mo Kα radiation. Friedel mates were merged (MERG 4) and the absolute configuration was not determined.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O11.00908 (19)0.47529 (18)0.35582 (9)0.0281 (4)
O20.85897 (19)0.47478 (17)0.23631 (9)0.0268 (4)
O30.5232 (2)0.2735 (2)0.39057 (11)0.0422 (5)
O40.6510 (3)0.2494 (3)0.50205 (13)0.0617 (7)
N11.0730 (2)0.2952 (2)0.25504 (10)0.0249 (4)
H11.05990.19190.25770.030*
C10.7998 (3)0.2734 (2)0.34181 (12)0.0243 (4)
C20.6576 (3)0.2247 (3)0.30806 (13)0.0253 (4)
H20.62850.26240.25890.030*
C30.5568 (3)0.1220 (3)0.34475 (13)0.0261 (5)
H30.46260.08880.31950.031*
C40.5932 (3)0.0679 (3)0.41775 (13)0.0263 (5)
C50.7326 (3)0.1174 (3)0.45272 (13)0.0296 (5)
H50.75890.08270.50280.035*
C60.8342 (3)0.2173 (3)0.41551 (13)0.0276 (5)
H60.92940.24820.44060.033*
C71.1685 (3)0.4963 (3)0.33084 (14)0.0302 (5)
H7A1.23820.52540.37440.036*
H7B1.17430.57470.29060.036*
C81.2172 (3)0.3441 (3)0.29856 (15)0.0313 (5)
H8A1.31080.35340.26410.038*
H8B1.24270.27290.34050.038*
C90.8982 (3)0.4085 (3)0.16438 (13)0.0283 (5)
H9A0.89390.48390.12260.034*
H9B0.82310.32630.15200.034*
C101.0671 (3)0.3484 (3)0.17388 (14)0.0297 (5)
H10A1.08750.26500.13760.036*
H10B1.14690.42830.16490.036*
C110.4878 (3)0.0470 (3)0.45767 (13)0.0287 (5)
H11A0.47170.01730.51200.034*
H11B0.38210.04980.43230.034*
C120.5624 (3)0.1999 (3)0.45463 (15)0.0330 (5)
C130.5926 (4)0.4222 (3)0.3835 (2)0.0499 (8)
H13A0.70930.41430.38310.060*
H13B0.55630.46860.33540.060*
H13C0.55890.48400.42720.060*
B10.9234 (3)0.3847 (3)0.30025 (14)0.0236 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0291 (8)0.0257 (8)0.0296 (8)0.0045 (7)0.0027 (6)0.0029 (7)
O20.0318 (8)0.0203 (7)0.0283 (8)0.0029 (7)0.0023 (7)0.0014 (6)
O30.0412 (10)0.0352 (10)0.0503 (10)0.0057 (9)0.0049 (9)0.0132 (9)
O40.0875 (17)0.0522 (12)0.0453 (11)0.0243 (14)0.0164 (12)0.0011 (9)
N10.0271 (9)0.0181 (8)0.0295 (9)0.0004 (8)0.0027 (8)0.0024 (8)
C10.0254 (10)0.0195 (10)0.0279 (10)0.0014 (9)0.0055 (8)0.0020 (9)
C20.0263 (10)0.0228 (10)0.0268 (10)0.0030 (9)0.0023 (9)0.0005 (9)
C30.0232 (10)0.0234 (10)0.0318 (11)0.0010 (9)0.0011 (9)0.0018 (9)
C40.0289 (10)0.0213 (10)0.0286 (10)0.0009 (9)0.0075 (9)0.0026 (9)
C50.0360 (12)0.0291 (11)0.0236 (10)0.0050 (10)0.0014 (10)0.0013 (9)
C60.0282 (10)0.0270 (11)0.0276 (10)0.0031 (10)0.0000 (9)0.0030 (9)
C70.0285 (11)0.0286 (12)0.0334 (12)0.0054 (10)0.0020 (9)0.0032 (10)
C80.0262 (11)0.0284 (12)0.0393 (13)0.0005 (10)0.0021 (10)0.0054 (10)
C90.0349 (12)0.0233 (11)0.0266 (11)0.0002 (10)0.0020 (9)0.0003 (9)
C100.0347 (12)0.0259 (11)0.0285 (11)0.0016 (10)0.0062 (10)0.0010 (9)
C110.0308 (11)0.0261 (11)0.0291 (11)0.0023 (9)0.0051 (9)0.0008 (9)
C120.0345 (12)0.0316 (12)0.0330 (11)0.0013 (11)0.0057 (10)0.0010 (10)
C130.0444 (15)0.0340 (14)0.071 (2)0.0026 (13)0.0060 (15)0.0162 (15)
B10.0261 (12)0.0188 (11)0.0258 (11)0.0004 (10)0.0020 (10)0.0009 (9)
Geometric parameters (Å, °) top
O1—C71.417 (3)C5—C61.392 (3)
O1—B11.449 (3)C5—H50.9500
O2—C91.421 (3)C6—H60.9500
O2—B11.474 (3)C7—C81.525 (4)
O3—C121.333 (3)C7—H7A0.9900
O3—C131.455 (4)C7—H7B0.9900
O4—C121.193 (3)C8—H8A0.9900
N1—C101.488 (3)C8—H8B0.9900
N1—C81.491 (3)C9—C101.523 (3)
N1—B11.681 (3)C9—H9A0.9900
N1—H10.9300C9—H9B0.9900
C1—C21.397 (3)C10—H10A0.9900
C1—C61.405 (3)C10—H10B0.9900
C1—B11.607 (3)C11—C121.502 (3)
C2—C31.400 (3)C11—H11A0.9900
C2—H20.9500C11—H11B0.9900
C3—C41.391 (3)C13—H13A0.9800
C3—H30.9500C13—H13B0.9800
C4—C51.388 (3)C13—H13C0.9800
C4—C111.520 (3)
C7—O1—B1109.67 (18)N1—C8—H8B111.1
C9—O2—B1110.55 (17)C7—C8—H8B111.1
C12—O3—C13114.9 (2)H8A—C8—H8B109.1
C10—N1—C8114.44 (19)O2—C9—C10105.45 (19)
C10—N1—B1105.44 (17)O2—C9—H9A110.7
C8—N1—B1103.17 (17)C10—C9—H9A110.7
C10—N1—H1111.1O2—C9—H9B110.7
C8—N1—H1111.1C10—C9—H9B110.7
B1—N1—H1111.1H9A—C9—H9B108.8
C2—C1—C6116.5 (2)N1—C10—C9104.23 (19)
C2—C1—B1123.6 (2)N1—C10—H10A110.9
C6—C1—B1119.9 (2)C9—C10—H10A110.9
C1—C2—C3121.8 (2)N1—C10—H10B110.9
C1—C2—H2119.1C9—C10—H10B110.9
C3—C2—H2119.1H10A—C10—H10B108.9
C4—C3—C2120.7 (2)C12—C11—C4110.81 (19)
C4—C3—H3119.7C12—C11—H11A109.5
C2—C3—H3119.7C4—C11—H11A109.5
C5—C4—C3118.2 (2)C12—C11—H11B109.5
C5—C4—C11120.3 (2)C4—C11—H11B109.5
C3—C4—C11121.5 (2)H11A—C11—H11B108.1
C4—C5—C6121.0 (2)O4—C12—O3123.2 (3)
C4—C5—H5119.5O4—C12—C11124.8 (3)
C6—C5—H5119.5O3—C12—C11112.0 (2)
C5—C6—C1121.7 (2)O3—C13—H13A109.5
C5—C6—H6119.1O3—C13—H13B109.5
C1—C6—H6119.1H13A—C13—H13B109.5
O1—C7—C8104.28 (19)O3—C13—H13C109.5
O1—C7—H7A110.9H13A—C13—H13C109.5
C8—C7—H7A110.9H13B—C13—H13C109.5
O1—C7—H7B110.9O1—B1—O2112.28 (19)
C8—C7—H7B110.9O1—B1—C1111.41 (18)
H7A—C7—H7B108.9O2—B1—C1116.1 (2)
N1—C8—C7103.34 (19)O1—B1—N1101.97 (18)
N1—C8—H8A111.1O2—B1—N1100.39 (17)
C7—C8—H8A111.1C1—B1—N1113.35 (18)
Hydrogen-bond geometry (Å, °) top
Cg3 is the centroid of the C1–C6 ring.
D—H···AD—HH···AD···AD—H···A
N1—H1···O2i0.932.062.921 (2)154
C10—H10B···Cg3ii0.992.653.618 (2)166
Symmetry codes: (i) −x+2, y−1/2, −z+1/2; (ii) −x+2, y+1/2, −z+1/2.
Table 1
Hydrogen-bond geometry (Å, °)
top
Cg3 is the centroid of the C1–C6 ring.
D—H···AD—HH···AD···AD—H···A
N1—H1···O2i0.932.062.921 (2)154
C10—H10B···Cg3ii0.992.653.618 (2)166
Symmetry codes: (i) −x+2, y−1/2, −z+1/2; (ii) −x+2, y+1/2, −z+1/2.
Acknowledgements top

We thank the NSERC and the Department of Chemistry for financial support. We are also grateful to the Ministry for Higher Education, Egypt, for a scholarship to ALZ.

references
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