[2,2′-Imino­diethano­lato(2−)-κ3 O,N,O′][4-(meth­oxy­carbonyl­meth­yl)phen­yl]boron

Ahmed L Zein; Louise N Dawe; Paris E Georghiou

doi:10.1107/S1600536810037864

. 2010 Sep 30;66(Pt 10):o2646. doi: 10.1107/S1600536810037864

[2,2′-Iminodiethanolato(2−)-κ³ O,N,O′][4-(methoxycarbonylmethyl)phenyl]boron

Ahmed L Zein ^a, Louise N Dawe ^a, Paris E Georghiou ^a,^*

PMCID: PMC2983237 PMID: 21587617

Abstract

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⋯π interactions leads to the pairwise association of molecules.

Related literature

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 & Suzuki (1995 ▶); Corey et al. (1987 ▶); Liu et al. (2007 ▶); Jung & Lazarova (1999 ▶); Chan et al. (1998 ▶); Evans et al. (1998 ▶); Lam et al. (1998 ▶). For related structures, see: Rettig & Trotter (1975 ▶); Wang & Georghiou (2002 ▶).

Experimental

Crystal data

C₁₃H₁₈BNO₄
M _r = 263.10
Orthorhombic,
a = 8.3776 (11) Å
b = 8.9269 (11) Å
c = 17.369 (2) Å
V = 1299.0 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 153 K
0.30 × 0.09 × 0.06 mm

Data collection

Rigaku Saturn diffractometer
Absorption correction: numerical (NUMABS; Higashi, 1999 ▶) T _min = 0.985, T _max = 0.997
16363 measured reflections
1725 independent reflections
1707 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.043
wR(F ²) = 0.112
S = 1.17
1725 reflections
173 parameters
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: CrystalClear (Rigaku, 2002 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; 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 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810037864/fj2337sup1.cif

e-66-o2646-sup1.cif^{(17KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810037864/fj2337Isup2.hkl

e-66-o2646-Isup2.hkl^{(85KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

Cg3 is the centroid of the C1–C6 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O2ⁱ	0.93	2.06	2.921 (2)	154
C10—H10B⋯Cg3ⁱⁱ	0.99	2.65	3.618 (2)	166

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

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.

supplementary crystallographic information

Comment

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 K_a 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).

Experimental

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.