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The furan ring in the title compound, C5H5BO4, is planar and each of the formyl and boronic groups makes a dihedral angle of ca 3° with this ring. The geometry of the furan ring is somewhat different to that found for substituted and unsubstituted furan structures. The mol­ecules are connected to each other in the bc plane by C—H...O and O—H...O hydrogen bonds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803017999/bt6327sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803017999/bt6327Isup2.hkl
Contains datablock I

CCDC reference: 222871

Key indicators

  • Single-crystal X-ray study
  • T = 100 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.047
  • wR factor = 0.132
  • Data-to-parameter ratio = 10.1

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low ....... 0.99 PLAT250_ALERT_2_C Large U3/U1 ratio for average U(i,j) tensor .... 2.08
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 2 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 1 ALERT type 2 Indicator that the structure model may be wrong or deficient 1 ALERT type 3 Indicator that the structure quality may be low 0 ALERT type 4 Improvement, methodology, query or suggestion

Comment top

Arylboronic acids, ArB(OH)2, have been known since the end of the nineteenth century. However, attention has recently been paid to these compounds owing to their new applications (Cuthbertson, 1998). The main synthetic application is Suzuki coupling: reaction of aryl halides with arylboronic acids (Miyaura et al., 1981; Miyaura & Suzuki, 1995; ChemFiles 2003). Other applications are asymmetric synthesis using chiral boronic acids (Currie et al., 2000) or analytical use as molecular sensors (Ward et al., 2002). These compounds are also used in medicine, e.g. for boron neutron-capture therapy (BNCT) (Soloway et al., 1998) or as virus enzyme inhibitors (Priestley & Decicco, 2000). There are only a few examples of the crystal structures of boronic acids. In these structures, the B(OH)2 group is attached to the phenyl ring (Feulner et al., 1990; Gainsford et al., 1995; Scouten et al., 1994), pyridine ring (Parry et al., 2002) or five-membered cyclopentadienyl ring (Norrild & Sotofte, 2001).

We present here the crystal structure of 5-formyl-2-furanboronic acid, (I), in which the boronic acid group is a substitutent of the furan ring. The B—O bond lengths are different, the B6—O7 bond being shorter than the B6—O8 bond by about 0.02A%. Similar differences have been reported for 4-carboxy-2-nitrobenzeneboronic acid (Soundararajan et al., 1993) and L-p-boronophenylalanine (Shull et al., 2000). The bond angles around atom B6 are distorted from the value of 120°; the O8–B6–C2 angle is 3.8° greater than 120°, whereas the O7–B6–C2 angle is 4.9° less than 120° and O7–B6–O8 is closest to the expected value. A similar geometry of the B(OH)2 acid group is observed in 2-bromo-5-pyridylboronic acid structures (Parry et al., 2002). The formyl and B(OH)2 groups in (I) are essentially coplanar with the furan ring. The dihedral angles of these planes with the furan ring are less than 3°. The five atoms of the furan ring are coplanar. The geometry of the furan ring in (I) is somewhat different to that of both unsubstituted furan rings [(II); Fourme, 1972] and substituted 5-nitro-2-furancarboxylic acid [(III); Alcock et al., 1996]. The C3—C4 bond length is similar to that found in (III) but it is shorter than that observed in (II) by ca 0.25 Å. The remaining bond lengths viz. C—Cα (C2—C3 and C4—C5) and O—Cα (O1—C2 and O1—C5) are slightly different from those observed in (II) and (III). The O—Cα—C and Cα—O—Cα angles in the furane ring of (I) are closer to those in (II) than in (III).

The molecular network in the crystal consists of two nearly linear strong O–H···O and one weak C–H···O hydrogen bonds. The O7–H7···O8 hydrogen bond forms dimers of (I); this is characteristic for arylboronic acids in solid state (Alcock et al., 1996; Feulner et al., 1990; Gainsford et al., 1995; Scouten et al., 1994).

Experimental top

5-formyl-2-furanboronic acid was obtained from Aldrich.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2002); cell refinement: CrysAlis RED (Oxford Diffraction, 2002); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXTL (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The packing diagram of the title compound, showing the hydrogen-bonding scheme (dashed lines).
(I) top
Crystal data top
C5H5BO4F(000) = 288
Mr = 139.90Dx = 1.542 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 3391 reflections
a = 3.7550 (8) Åθ = 3.3–25.5°
b = 7.758 (2) ŵ = 0.13 mm1
c = 20.694 (4) ÅT = 100 K
β = 91.31 (3)°Cube, colourless
V = 602.7 (2) Å30.20 × 0.18 × 0.16 mm
Z = 4
Data collection top
Xcalibur
diffractometer
764 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.089
Graphite monochromatorθmax = 25.5°, θmin = 3.3°
Detector resolution: 1024 x 1024 with blocks 2 x 2 pixels mm-1h = 43
ω scansk = 99
3391 measured reflectionsl = 2525
1126 independent 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)] = 0.047Hydrogen site location: difference Fourier map
wR(F2) = 0.132All H-atom parameters refined
S = 0.95 w = 1/[σ2(Fo2) + (0.0811P)2]
where P = (Fo2 + 2Fc2)/3
1126 reflections(Δ/σ)max < 0.001
111 parametersΔρmax = 0.16 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C5H5BO4V = 602.7 (2) Å3
Mr = 139.90Z = 4
Monoclinic, P21/nMo Kα radiation
a = 3.7550 (8) ŵ = 0.13 mm1
b = 7.758 (2) ÅT = 100 K
c = 20.694 (4) Å0.20 × 0.18 × 0.16 mm
β = 91.31 (3)°
Data collection top
Xcalibur
diffractometer
764 reflections with I > 2σ(I)
3391 measured reflectionsRint = 0.089
1126 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0470 restraints
wR(F2) = 0.132All H-atom parameters refined
S = 0.95Δρmax = 0.16 e Å3
1126 reflectionsΔρmin = 0.21 e Å3
111 parameters
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.4972 (4)0.36605 (18)0.16766 (6)0.0377 (5)
C20.3680 (6)0.3652 (3)0.10461 (10)0.0370 (6)
C30.2287 (6)0.5230 (3)0.09057 (11)0.0435 (6)
C40.2760 (6)0.6270 (3)0.14538 (11)0.0439 (6)
C50.4390 (6)0.5284 (3)0.19130 (10)0.0368 (5)
B60.4052 (7)0.2001 (3)0.06251 (12)0.0404 (6)
O70.2772 (5)0.2141 (2)0.00177 (7)0.0545 (6)
O80.5605 (5)0.0522 (2)0.08392 (8)0.0516 (6)
C90.5554 (6)0.5719 (3)0.25553 (11)0.0442 (6)
O100.7116 (5)0.4754 (2)0.29327 (7)0.0550 (5)
H90.502 (6)0.697 (4)0.2692 (11)0.058 (7)*
H30.128 (5)0.556 (3)0.0477 (11)0.046 (6)*
H40.209 (7)0.745 (4)0.1508 (13)0.070 (8)*
H70.325 (9)0.114 (5)0.0258 (16)0.094 (11)*
H80.617 (7)0.048 (4)0.1224 (14)0.065 (8)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0528 (9)0.0329 (8)0.0270 (8)0.0032 (7)0.0068 (6)0.0006 (6)
C20.0429 (12)0.0398 (12)0.0280 (11)0.0003 (10)0.0049 (9)0.0004 (9)
C30.0530 (14)0.0414 (13)0.0357 (13)0.0039 (11)0.0082 (10)0.0020 (10)
C40.0522 (14)0.0354 (12)0.0439 (13)0.0038 (11)0.0056 (11)0.0002 (10)
C50.0446 (12)0.0320 (12)0.0338 (12)0.0012 (9)0.0002 (9)0.0044 (9)
B60.0509 (15)0.0411 (14)0.0289 (13)0.0032 (12)0.0022 (10)0.0002 (10)
O70.0849 (13)0.0459 (10)0.0319 (9)0.0161 (9)0.0150 (8)0.0052 (7)
O80.0854 (13)0.0411 (10)0.0276 (9)0.0128 (9)0.0132 (8)0.0028 (7)
C90.0568 (15)0.0404 (13)0.0353 (13)0.0046 (11)0.0015 (11)0.0054 (10)
O100.0816 (13)0.0501 (11)0.0326 (9)0.0018 (9)0.0123 (8)0.0002 (7)
Geometric parameters (Å, º) top
O1—C51.371 (2)C5—C91.430 (3)
O1—C21.382 (2)B6—O71.340 (3)
C2—C31.360 (3)B6—O81.357 (3)
C2—B61.557 (3)O7—H70.98 (4)
C3—C41.400 (3)O8—H80.82 (3)
C3—H30.99 (2)C9—O101.222 (3)
C4—C51.355 (3)C9—H91.03 (3)
C4—H40.95 (3)
C5—O1—C2106.6 (2)C4—C5—C9130.0 (2)
C3—C2—O1108.8 (2)O1—C5—C9120.0 (2)
C3—C2—B6131.3 (2)O7—B6—O8121.1 (2)
O1—C2—B6119.9 (2)O7—B6—C2115.1 (2)
C2—C3—C4107.7 (2)O8—B6—C2123.8 (2)
C2—C3—H3124.0 (14)B6—O7—H7114.5 (19)
C4—C3—H3128.2 (14)B6—O8—H8116.8 (19)
C5—C4—C3106.8 (2)O10—C9—C5125.6 (2)
C5—C4—H4125.0 (16)O10—C9—H9119.5 (14)
C3—C4—H4128.1 (17)C5—C9—H9114.9 (14)
C4—C5—O1110.0 (2)
C5—O1—C2—C31.0 (2)C2—O1—C5—C9178.0 (2)
C5—O1—C2—B6177.8 (2)C3—C2—B6—O70.3 (4)
O1—C2—C3—C41.0 (3)O1—C2—B6—O7178.8 (2)
B6—C2—C3—C4177.6 (2)C3—C2—B6—O8178.4 (2)
C2—C3—C4—C50.7 (3)O1—C2—B6—O80.1 (4)
C3—C4—C5—O10.1 (3)C4—C5—C9—O10177.5 (2)
C3—C4—C5—C9178.4 (2)O1—C5—C9—O100.7 (4)
C2—O1—C5—C40.5 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O7—H7···O8i0.98 (4)1.82 (4)2.799 (2)173 (3)
O8—H8···O10ii0.82 (3)1.93 (3)2.729 (2)164 (3)
C3—H3···O7iii0.99 (2)2.55 (2)3.355 (3)139 (2)
Symmetry codes: (i) x+1, y, z; (ii) x+3/2, y1/2, z+1/2; (iii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaC5H5BO4
Mr139.90
Crystal system, space groupMonoclinic, P21/n
Temperature (K)100
a, b, c (Å)3.7550 (8), 7.758 (2), 20.694 (4)
β (°) 91.31 (3)
V3)602.7 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.13
Crystal size (mm)0.20 × 0.18 × 0.16
Data collection
DiffractometerXcalibur
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3391, 1126, 764
Rint0.089
(sin θ/λ)max1)0.605
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.047, 0.132, 0.95
No. of reflections1126
No. of parameters111
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.16, 0.21

Computer programs: CrysAlis CCD (Oxford Diffraction, 2002), CrysAlis RED (Oxford Diffraction, 2002), CrysAlis RED, SHELXTL (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL, SHELXL97.

Selected geometric parameters (Å, º) top
O1—C51.371 (2)C4—C51.355 (3)
O1—C21.382 (2)C5—C91.430 (3)
C2—C31.360 (3)B6—O71.340 (3)
C2—B61.557 (3)B6—O81.357 (3)
C3—C41.400 (3)C9—O101.222 (3)
C5—O1—C2106.6 (2)C4—C5—C9130.0 (2)
C3—C2—O1108.8 (2)O1—C5—C9120.0 (2)
C3—C2—B6131.3 (2)O7—B6—O8121.1 (2)
O1—C2—B6119.9 (2)O7—B6—C2115.1 (2)
C2—C3—C4107.7 (2)O8—B6—C2123.8 (2)
C5—C4—C3106.8 (2)O10—C9—C5125.6 (2)
C4—C5—O1110.0 (2)
C5—O1—C2—B6177.8 (2)O1—C2—B6—O7178.8 (2)
B6—C2—C3—C4177.6 (2)C3—C2—B6—O8178.4 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O7—H7···O8i0.98 (4)1.82 (4)2.799 (2)173 (3)
O8—H8···O10ii0.82 (3)1.93 (3)2.729 (2)164 (3)
C3—H3···O7iii0.99 (2)2.55 (2)3.355 (3)139 (2)
Symmetry codes: (i) x+1, y, z; (ii) x+3/2, y1/2, z+1/2; (iii) x, y+1, z.
 

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