supplementary materials
tert-Butyl 2-borono-1H-pyrrole-1-carboxylate
In the crystal structure of the title compound, C9H14BNO4, the boronic acid group and carbamate groups are nearly co-planar with the pyrrole ring, making dihedral angles of 0.1 (2) and 2.2 (2)°, respectively. Intramolecular and intermolecular O-H
O hydrogen bonds help to stabilize the structure, the latter interaction leading to inversion dimers..
All chemical reagents are commercial and used as received. Under -78°C and
argon atmosphere, lithium diisopropylamide (1.0 M in THF, 5.0 ml, 5.0 mmol) was added dropwise to a solution of tert-butyl
1H-pyrrole-1-carboxylate (835 mg, 5.0 mmol) in dry THF (15 ml), and the
solution was stirred at this temperature for 30 min. Trimethylborate (1.7 ml,
15 mmol) was added dropwise, and the mixture was allowed to warm to room
temperature over 2 h and stirred overnight. After aqueous workup, the crude
product was crystallized from hexanes. Single crystals suitable for X-ray
analysis were obtained by recrystallization from a mixed solvent of ethyl
acetate and hexane at ambient temperature (20–25°C).
H atoms were located in a difference Fourier map and refined isotropically.
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Tert-butyl 2-borono-1
H-pyrrole-1-carboxylate
top
Crystal data top
| C9H14BNO4 | F(000) = 896 |
| Mr = 211.02 | Dx = 1.244 Mg m−3 |
| Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ac 2ab | Cell parameters from 810 reflections |
| a = 13.014 (3) Å | θ = 2.3–22.4° |
| b = 9.940 (2) Å | µ = 0.10 mm−1 |
| c = 17.417 (4) Å | T = 293 K |
| V = 2252.9 (9) Å3 | Prism, colorless |
| Z = 8 | 0.25 × 0.12 × 0.10 mm |
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer | 1208 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.065 |
| graphite | θmax = 26.0°, θmin = 2.3° |
| φ and ω scans | h = −16→13 |
| 9542 measured reflections | k = −12→12 |
| 2213 independent reflections | l = −21→19 |
Refinement top
| 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)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.106 | All H-atom parameters refined |
| S = 0.85 | w = 1/[σ2(Fo2) + (0.0588P)2]
where P = (Fo2 + 2Fc2)/3 |
| 2213 reflections | (Δ/σ)max < 0.001 |
| 192 parameters | Δρmax = 0.12 e Å−3 |
| 0 restraints | Δρmin = −0.20 e Å−3 |
Crystal data top
| C9H14BNO4 | V = 2252.9 (9) Å3 |
| Mr = 211.02 | Z = 8 |
| Orthorhombic, Pbca | Mo Kα radiation |
| a = 13.014 (3) Å | µ = 0.10 mm−1 |
| b = 9.940 (2) Å | T = 293 K |
| c = 17.417 (4) Å | 0.25 × 0.12 × 0.10 mm |
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer | 1208 reflections with I > 2σ(I) |
| 9542 measured reflections | Rint = 0.065 |
| 2213 independent reflections | θmax = 26.0° |
Refinement top
| R[F2 > 2σ(F2)] = 0.042 | All H-atom parameters refined |
| wR(F2) = 0.106 | Δρmax = 0.12 e Å−3 |
| S = 0.85 | Δρmin = −0.20 e Å−3 |
| 2213 reflections | Absolute structure: ? |
| 192 parameters | Flack parameter: ? |
| 0 restraints | Rogers 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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| B1 | 1.03949 (15) | 0.6990 (2) | 0.51802 (11) | 0.0727 (6) | |
| C1 | 1.09811 (14) | 1.0494 (2) | 0.59196 (12) | 0.0767 (5) | |
| C2 | 1.17519 (16) | 1.0274 (3) | 0.54329 (13) | 0.0893 (7) | |
| C3 | 1.16298 (14) | 0.8995 (3) | 0.51194 (12) | 0.0821 (6) | |
| C4 | 1.07732 (12) | 0.83956 (18) | 0.54116 (8) | 0.0644 (5) | |
| C5 | 0.94986 (12) | 0.92187 (19) | 0.63777 (9) | 0.0635 (4) | |
| C6 | 0.85439 (15) | 1.03344 (19) | 0.74024 (10) | 0.0771 (5) | |
| C7 | 0.75166 (18) | 1.0282 (3) | 0.70204 (16) | 0.0955 (7) | |
| C8 | 0.8711 (3) | 0.9215 (3) | 0.79700 (14) | 0.1000 (7) | |
| C9 | 0.8746 (3) | 1.1693 (3) | 0.7756 (2) | 0.1119 (9) | |
| N1 | 1.03646 (9) | 0.93560 (14) | 0.59221 (7) | 0.0631 (4) | |
| O1 | 0.93714 (8) | 1.02801 (13) | 0.68119 (7) | 0.0754 (4) | |
| O2 | 0.89519 (9) | 0.82427 (13) | 0.63724 (7) | 0.0776 (4) | |
| O3 | 0.95566 (10) | 0.63485 (15) | 0.54641 (8) | 0.0921 (5) | |
| O4 | 1.09809 (10) | 0.6338 (2) | 0.46635 (8) | 0.0960 (5) | |
| H3 | 1.2044 (14) | 0.8510 (17) | 0.4741 (10) | 0.083 (5)* | |
| H7A | 0.7006 (17) | 1.040 (2) | 0.7397 (13) | 0.104 (7)* | |
| H7B | 0.7430 (18) | 1.106 (3) | 0.6664 (14) | 0.131 (10)* | |
| H8A | 0.8247 (16) | 0.934 (2) | 0.8403 (14) | 0.109 (7)* | |
| H1 | 1.0760 (14) | 1.126 (2) | 0.6241 (11) | 0.089 (6)* | |
| H9A | 0.8259 (16) | 1.184 (2) | 0.8132 (14) | 0.122 (8)* | |
| H9B | 0.8706 (15) | 1.236 (2) | 0.7359 (14) | 0.109 (9)* | |
| H7C | 0.7384 (15) | 0.942 (2) | 0.6764 (13) | 0.104 (7)* | |
| H2 | 1.2262 (17) | 1.090 (2) | 0.5323 (11) | 0.104 (7)* | |
| H8B | 0.941 (2) | 0.928 (2) | 0.8167 (14) | 0.130 (9)* | |
| H9C | 0.949 (2) | 1.169 (3) | 0.7937 (16) | 0.169 (12)* | |
| H8C | 0.8565 (17) | 0.826 (3) | 0.7735 (14) | 0.135 (9)* | |
| H3A | 0.9265 (14) | 0.6888 (19) | 0.5791 (11) | 0.087 (6)* | |
| H4 | 1.080 (2) | 0.548 (3) | 0.4581 (16) | 0.145 (12)* | |
Atomic displacement parameters (Å2) top| | U11 | U22 | U33 | U12 | U13 | U23 |
| B1 | 0.0572 (11) | 0.1046 (17) | 0.0563 (11) | 0.0146 (11) | −0.0040 (9) | −0.0053 (11) |
| C1 | 0.0616 (11) | 0.0916 (15) | 0.0767 (12) | −0.0077 (11) | −0.0134 (10) | 0.0135 (12) |
| C2 | 0.0590 (12) | 0.120 (2) | 0.0888 (15) | −0.0117 (12) | −0.0074 (11) | 0.0335 (14) |
| C3 | 0.0565 (11) | 0.1260 (19) | 0.0638 (11) | 0.0091 (12) | 0.0003 (9) | 0.0161 (13) |
| C4 | 0.0524 (9) | 0.0915 (13) | 0.0492 (8) | 0.0113 (9) | −0.0034 (7) | 0.0069 (9) |
| C5 | 0.0586 (10) | 0.0744 (12) | 0.0576 (9) | 0.0032 (9) | −0.0030 (8) | 0.0004 (9) |
| C6 | 0.0834 (13) | 0.0832 (13) | 0.0647 (11) | 0.0110 (10) | 0.0065 (9) | −0.0149 (10) |
| C7 | 0.0793 (15) | 0.116 (2) | 0.0913 (17) | 0.0166 (14) | 0.0054 (13) | −0.0170 (17) |
| C8 | 0.119 (2) | 0.115 (2) | 0.0655 (13) | 0.0172 (16) | 0.0126 (14) | 0.0019 (14) |
| C9 | 0.129 (2) | 0.103 (2) | 0.103 (2) | 0.0076 (16) | 0.0117 (18) | −0.0376 (18) |
| N1 | 0.0494 (7) | 0.0814 (10) | 0.0585 (8) | −0.0007 (7) | −0.0031 (6) | 0.0075 (7) |
| O1 | 0.0787 (8) | 0.0766 (8) | 0.0708 (7) | −0.0010 (6) | 0.0069 (6) | −0.0128 (7) |
| O2 | 0.0698 (7) | 0.0786 (9) | 0.0844 (8) | −0.0067 (6) | 0.0214 (6) | −0.0166 (7) |
| O3 | 0.0730 (8) | 0.1037 (11) | 0.0996 (10) | −0.0004 (7) | 0.0200 (7) | −0.0384 (8) |
| O4 | 0.0799 (9) | 0.1217 (14) | 0.0863 (9) | 0.0147 (8) | 0.0190 (7) | −0.0238 (9) |
Geometric parameters (Å, °) top
| B1—O4 | 1.346 (2) | C6—C7 | 1.494 (3) |
| B1—O3 | 1.357 (2) | C6—C8 | 1.504 (3) |
| B1—C4 | 1.535 (3) | C6—C9 | 1.507 (3) |
| C1—C2 | 1.331 (3) | C7—H7A | 0.94 (2) |
| C1—N1 | 1.387 (2) | C7—H7B | 0.99 (3) |
| C1—H1 | 0.99 (2) | C7—H7C | 0.98 (2) |
| C2—C3 | 1.393 (3) | C8—H8A | 0.97 (2) |
| C2—H2 | 0.93 (2) | C8—H8B | 0.98 (3) |
| C3—C4 | 1.363 (3) | C8—H8C | 1.05 (3) |
| C3—H3 | 0.978 (18) | C9—H9A | 0.92 (2) |
| C4—N1 | 1.409 (2) | C9—H9B | 0.96 (2) |
| C5—O2 | 1.2030 (19) | C9—H9C | 1.02 (3) |
| C5—O1 | 1.309 (2) | O3—H3A | 0.87 (2) |
| C5—N1 | 1.385 (2) | O4—H4 | 0.89 (3) |
| C6—O1 | 1.490 (2) | | |
| | | |
| O4—B1—O3 | 118.2 (2) | C6—C7—H7A | 108.5 (13) |
| O4—B1—C4 | 115.60 (19) | C6—C7—H7B | 110.6 (14) |
| O3—B1—C4 | 126.14 (17) | H7A—C7—H7B | 105.0 (18) |
| C2—C1—N1 | 107.7 (2) | C6—C7—H7C | 112.9 (12) |
| C2—C1—H1 | 135.0 (12) | H7A—C7—H7C | 107.4 (18) |
| N1—C1—H1 | 117.2 (11) | H7B—C7—H7C | 112 (2) |
| C1—C2—C3 | 108.3 (2) | C6—C8—H8A | 109.2 (12) |
| C1—C2—H2 | 123.9 (13) | C6—C8—H8B | 108.4 (15) |
| C3—C2—H2 | 127.8 (13) | H8A—C8—H8B | 107 (2) |
| C4—C3—C2 | 110.3 (2) | C6—C8—H8C | 112.7 (13) |
| C4—C3—H3 | 119.1 (11) | H8A—C8—H8C | 107.5 (18) |
| C2—C3—H3 | 130.7 (10) | H8B—C8—H8C | 111 (2) |
| C3—C4—N1 | 104.36 (18) | C6—C9—H9A | 107.9 (16) |
| C3—C4—B1 | 124.22 (18) | C6—C9—H9B | 108.3 (13) |
| N1—C4—B1 | 131.40 (15) | H9A—C9—H9B | 112 (2) |
| O2—C5—O1 | 125.44 (15) | C6—C9—H9C | 107.0 (17) |
| O2—C5—N1 | 123.79 (16) | H9A—C9—H9C | 116 (2) |
| O1—C5—N1 | 110.77 (15) | H9B—C9—H9C | 106 (2) |
| O1—C6—C7 | 109.75 (16) | C5—N1—C1 | 123.57 (16) |
| O1—C6—C8 | 108.80 (16) | C5—N1—C4 | 127.01 (15) |
| C7—C6—C8 | 113.4 (2) | C1—N1—C4 | 109.41 (16) |
| O1—C6—C9 | 100.86 (18) | C5—O1—C6 | 121.30 (13) |
| C7—C6—C9 | 111.6 (2) | B1—O3—H3A | 107.4 (12) |
| C8—C6—C9 | 111.6 (2) | B1—O4—H4 | 114.5 (18) |
Hydrogen-bond geometry (Å, °) top
| D—H···A | D—H | H···A | D···A | D—H···A |
| O4—H4···O3i | 0.89 (3) | 1.88 (3) | 2.769 (3) | 173 (3) |
| O3—H3A···O2 | 0.87 (2) | 1.73 (2) | 2.5819 (18) | 164.7 (18) |
| Symmetry codes: (i) −x+2, −y+1, −z+1. |
Table 1
Hydrogen-bond geometry (Å, °) top
| D—H···A | D—H | H···A | D···A | D—H···A |
| O4—H4···O3i | 0.89 (3) | 1.88 (3) | 2.769 (3) | 173 (3) |
| O3—H3A···O2 | 0.87 (2) | 1.73 (2) | 2.5819 (18) | 164.7 (18) |
| Symmetry codes: (i) −x+2, −y+1, −z+1. |
We thank Professor Lin-Hong Weng, Fudan University, for the X-ray analysis.
Bruker (2001). SAINT and SMART. Bruker AXS Inc., Madison, Wisconsin, USA.
Hall, D. G. (2005). Editor. Boronic Acids, Weinheim: Wiley-VCH.
Kelly, T. A. & Fuchs, V. U. (1993). Tetrahedron 49, 1009–1016.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
![[Figure 1]](./xu2484fig1thm.gif)
Boronic acids are versatile compounds widely used in the synthesis of biaryls, as therapeutical agents, and as chemical sensors (Hall, 2005). The title compound is the key intermediate for the synthesis of (+)-pinanediol-L-boroproline (Kelly & Fuchs, 1993).
In the molecular structure of the title compound (Fig. 1), the pyrrole ring, the boronic acid group and the carboxyl groups are almost co-planar. The carbonyl links with the adjacent boronic acid group via O3—H3···O2 hydrogen bonding. Intermolecular hydrogen bond is also observed in the crystal structure (Table 1).