[5-Hydroxy-3-phenyl-1-(pyridin-2-yl)pyrazol-5-olato]diphenylboron

Kee-In Lee; Hye-Rin Bin; Do-Min Lee; Chong-Hyeak Kim

doi:10.1107/S1600536811010634

. 2011 Mar 26;67(Pt 4):o979. doi: 10.1107/S1600536811010634

[5-Hydroxy-3-phenyl-1-(pyridin-2-yl)pyrazol-5-olato]diphenylboron

Kee-In Lee ^a, Hye-Rin Bin ^a, Do-Min Lee ^a, Chong-Hyeak Kim ^b,^*

PMCID: PMC3099986 PMID: 21754238

Abstract

In the title compound, C₂₆H₂₀BN₃O, the B atom has tetrahedral geometry and is linked to two phenyl rings, the O atom of the hydroxypyrazole ring and the N atom of the pyridinyl ring. A six-membered BOCNCN ring forms by coordination of the B atom and the pyridinyl N atom. The BOCNCN ring has an envelope conformation [dihedral angle = 36.7 (1)° between the planar ring atoms and the flap] with the B atom out of the plane. In the 1-(2-pyridinyl)-3-phenyl-5-hydroxypyrazole group, the pyridinyl ring, the phenyl ring and the pyrazole ring are almost coplanar: the pyrazole ring makes a dihedral angle of 9.56 (8)° with the pyridinyl ring and 17.68 (7)° with the phenyl ring. The crystal structure is stabilized by π–π stacking interactions involving the pyridinyl and pyrazole rings of centrosymmetrically related molecules, with ring centroid separations of 3.54 (5) Å.

Related literature

For general synthesis of diarylborinates, see: Hagan et al. (2000 ▶). For their synthesis and biological applications, see: Scorei & Popa (2010 ▶); Baker, Akama et al. (2006 ▶); Baker, Zhang et al. (2006 ▶). For luminescent organoboron compounds, see: Cui et al. (2005 ▶).

Experimental

Crystal data

C₂₆H₂₀BN₃O
M _r = 401.26
Triclinic,
a = 9.7309 (1) Å
b = 9.8830 (1) Å
c = 11.2162 (1) Å
α = 78.966 (1)°
β = 81.795 (1)°
γ = 79.993 (1)°
V = 1035.91 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 296 K
0.44 × 0.31 × 0.23 mm

Data collection

Bruker APEXII CCD diffractometer
19866 measured reflections
5044 independent reflections
3923 reflections with I > 2σ(I)
R _int = 0.019

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.106
S = 1.03
5044 reflections
280 parameters
H-atom parameters constrained
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; 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.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811010634/pk2309sup1.cif

e-67-0o979-sup1.cif^{(22.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811010634/pk2309Isup2.hkl

e-67-0o979-Isup2.hkl^{(247KB, hkl)}

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

supplementary crystallographic information

Comment

Recently, boron-containing compounds have become increasingly frequent in preventive and chemotherapeutic agents for high-malignancy cancer (Scorei & Popa, 2010), their antibacterial and antifungal agents effect on cell growth (Baker, Akama et al., 2006; Baker, Zhang et al., 2006), and also in luminescent compounds for potential applications in organic light emitting devices (Cui et al., 2005). Diarylborinates have been prepared by the reaction of diarylborinic acids with dimethylaminoethanol-type ligands (Hagan et al., 2000). Interestingly, we identify an unusual diphenylborinate from 1-(2-pyridinyl)pyrazole trifluoromethanesulfonate with phenylboronic acid in Suzuki-Miyaura coupling conditions. Here we report the crystal structure of the title compound (Figs. 1 and 2). In the title compound, C₂₆H₂₀BN₃O, B atom has a tetrahedral geometry linked with the two C atoms of the two phenyl rings, the O atom of the hydroxypyrazole ring and the N atom of the pyridinyl ring. The six membered ring of –B(19)—O(18)—C(5)—N(1)—C(6)—N(7)- motif forms by the coordination between B atom and N atom of the pyridinyl ring. The –B—O—C—N—C—N– ring has an envelope conformation with B out of plane. The B atom deviate from the the mean plane and forms a dihedral angle of 36.7 (1) ° with B(19)—O(18) 1.508 (2) Å and B(19)—N(7) 1.641 (2) Å. In the 1-(2-pyridinyl)-3-phenyl-5-hydroxypyrazole group the pyridinyl ring, the phenyl ring and the pyrazole ring are almost coplanar. The pyrazole ring makes a dihedral angle of 9.56 (8)° with the pyridinyl ring, and 17.68 (7)° with the phenyl ring. The crystal structure is stabilized by π-π stacking interactions involving the pyridinyl and pyrazole rings of centrosymmetrically related molecules, with a ring centroid separations of 3.54 (5) Å.

Experimental

The title compound was synthesized from the reaction of 1-(2-pyridinyl)pyrazole trifluoromethanesulfonate (185 mg, 0.5 mmol) and phenylboronic acid (183 mg, 1.5 mmol) with K₃PO₄ (318 mg, 1.5 mmol) in the presence of PdCl₂{1,1'-bis(diphenylphosphino)ferrocene} (33 mg, 0.04 mmol) and 1,1'-bis(diphenylphosphino)ferrocene (11 mg, 0.02 mmol) in anhydrous 1,4-dioxane (5 ml) for 20 hr at 100 °C. The reaction mixture was rinsed with toluene (5 ml) and the resulting solution was filtered by aid of a Celite pad. The organic layer was dried over Na₂SO₄ and the solvents were removed. The residue was purified by column chromatography on silica gel (hexane/ethyl acetate = 7/1) to give the title compound (30 mg, 8% yield). Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution in ethyl acetate at room temperature.