tert-Butyl 2-borono-1H-pyrrole-1-carboxyl­ate

Zheng Zhong; Guo-Qiang Lin; Zhi-Hua Sun; Bing Wang

doi:10.1107/S1600536809007375

. 2009 Mar 6;65(Pt 4):o687. doi: 10.1107/S1600536809007375

tert-Butyl 2-borono-1H-pyrrole-1-carboxylate

Zheng Zhong ^a, Guo-Qiang Lin ^a, Zhi-Hua Sun ^a, Bing Wang ^a,^*

PMCID: PMC2969006 PMID: 21582429

Abstract

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..

Related literature

For general background, see: Hall (2005 ▶); Kelly & Fuchs (1993 ▶).

Experimental

Crystal data

C₉H₁₄BNO₄
M _r = 211.02
Orthorhombic,
a = 13.014 (3) Å
b = 9.940 (2) Å
c = 17.417 (4) Å
V = 2252.9 (9) Å³
Z = 8
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 293 K
0.25 × 0.12 × 0.10 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction: none
9542 measured reflections
2213 independent reflections
1208 reflections with I > 2σ(I)
R _int = 0.065

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.106
S = 0.85
2213 reflections
192 parameters
All H-atom parameters refined
Δρ_max = 0.12 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT (Bruker, 2001 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S1600536809007375/xu2484sup1.cif

e-65-0o687-sup1.cif^{(15.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809007375/xu2484Isup2.hkl

e-65-0o687-Isup2.hkl^{(108.9KB, hkl)}

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3A⋯O2	0.87 (2)	1.73 (2)	2.5819 (18)	164.7 (18)
O4—H4⋯O3ⁱ	0.89 (3)	1.88 (3)	2.769 (3)	173 (3)

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Symmetry code: (i) Inline graphic .

Acknowledgments

We thank Professor Lin-Hong Weng, Fudan University, for the X-ray analysis.

supplementary crystallographic information

Comment

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).

Experimental

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).