1-Ethyl-1H-pyrazole-4-boronic acid, pinacol ester Chemical Properties

Melting point:

44-49°C

Boiling point:

322.6±15.0 °C(Predicted)

Density 

1.04±0.1 g/cm3(Predicted)

refractive index 

1.48

storage temp. 

under inert gas (nitrogen or Argon) at 2-8°C

form 

clear liquid

pka

2.11±0.10(Predicted)

color 

Colorless to Almost colorless

InChI

InChI=1S/C11H19BN2O2/c1-6-14-8-9(7-13-14)12-15-10(2,3)11(4,5)16-12/h7-8H,6H2,1-5H3

InChIKey

UGCRHVPUHAXAAE-UHFFFAOYSA-N

SMILES

N1(CC)C=C(B2OC(C)(C)C(C)(C)O2)C=N1

CAS DataBase Reference

847818-70-6

Safety Information

Hazard Codes 

Xi

Risk Statements 

36/37/38

Safety Statements 

26

WGK Germany 

3

HS Code 

2933199090

1-Ethyl-1H-pyrazole-4-boronic acid, pinacol ester Usage And Synthesis

Synthesis

To a solution of N,N-dimethylformamide (DMF, 10 mL) of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (1.0 g, 5.2 mmol) was added cesium carbonate (2.5 g, 7.7 mmol) and ethyl iodide (1.2 mL, 15 mmol). The reaction mixture was stirred at room temperature for 12 hours. After the reaction was completed, the reaction mixture was diluted with water (30 mL). The aqueous phase was extracted with dichloromethane (DCM, 30 mL x 3). The organic layers were combined and dried over anhydrous sodium sulfate (Na2SO4) and subsequently concentrated under reduced pressure. The residue was purified by silica gel column chromatography using petroleum ether (PE)/ethyl acetate (EtOAc) (2:1, v/v) as eluent to afford the colorless oily product 1-ethyl-1H-pyrazole-4-boronic acid pinacol ester (880 mg, 77% yield). Mass spectrometric (MS) analysis (electrospray ionization, cation mode) showed m/z: 223.25 [M + 1]+.

References

[1] Patent: WO2016/615, 2016, A1. Location in patent: Paragraph 00655
[2] Patent: EP1798229, 2007, A1. Location in patent: Page/Page column 130
[3] Patent: US2010/240634, 2010, A1. Location in patent: Page/Page column 67-68
[4] Patent: WO2018/102452, 2018, A2. Location in patent: Paragraph 425; 426
[5] Bioorganic and Medicinal Chemistry Letters, 2008, vol. 18, # 19, p. 5299 - 5302

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