1-Methyl-1H-pyrazole-5-boronic acid pinacol ester Chemical Properties

Melting point:

67-71 °C

Boiling point:

308.3±15.0 °C(Predicted)

Density 

1.05±0.1 g/cm3(Predicted)

storage temp. 

Inert atmosphere,Store in freezer, under -20°C

pka

1.94±0.10(Predicted)

form 

crystal

color 

white

Water Solubility 

Slightly soluble in water.

InChI

InChI=1S/C10H17BN2O2/c1-9(2)10(3,4)15-11(14-9)8-6-7-12-13(8)5/h6-7H,1-5H3

InChIKey

HLXOVAMYQUFLPE-UHFFFAOYSA-N

SMILES

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

CAS DataBase Reference

847818-74-0(CAS DataBase Reference)

Safety Information

Hazard Codes 

Xn

Risk Statements 

22-36/37/38

Safety Statements 

26

WGK Germany 

3

TSCA 

No

HazardClass 

IRRITANT

HS Code 

29349990

1-Methyl-1H-pyrazole-5-boronic acid pinacol ester Usage And Synthesis

Chemical Properties

White to light brown solid

Uses

1-Methyl-1H-pyrazole-5-boronic acid pinacol ester is used as a pharmaceutical intermediate, agrochemical intermediate.

Synthesis

To a solution of 1-methylpyrazole (4.1 g, 50 mmol) in tetrahydrofuran (THF, 100 mL) was slowly added n-butyllithium (n-BuLi, 2.2 M solution in THF, 55 mmol) at 0 °C. The reaction mixture was stirred at room temperature for 1 hour and then cooled to -78 °C. Subsequently, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (12.3 mL, 60 mmol) was added to the reaction system. The reaction was carried out at -78 °C for 15 min and then gradually warmed up to 0 °C, taking 1 hour. Upon completion of the reaction, the reaction was quenched with saturated ammonium chloride (NH4Cl) solution and extracted with dichloromethane (DCM). The organic phases were combined, washed with distilled water (2 × 100 mL), dried over anhydrous sodium sulfate (Na2SO4), and concentrated under reduced pressure to afford the brown solid product 1-methyl-1H-pyrazole-5-boronic acid pinacol ester (8.0 g, 77% yield), which could be used for the subsequent reaction without further purification. The product was detected by liquid chromatography-mass spectrometry (LCMS, ES), showing m/z 127 (M+H)+ [RB(OH)2]; nuclear magnetic resonance hydrogen spectroscopy (1H NMR, CDCl3, 400 MHz) showed δ 7.57 (s, 1H), 6.75 (s, 1H), 4.16 (s, 3H) and 1.41 (s, 12H).

References

[1] Patent: WO2009/158372, 2009, A1. Location in patent: Page/Page column 30; 31
[2] Patent: WO2009/158374, 2009, A2. Location in patent: Page/Page column 30
[3] Patent: WO2008/98105, 2008, A1. Location in patent: Page/Page column 36
[4] Patent: US2010/216843, 2010, A1. Location in patent: Page/Page column 20-21
[5] Patent: WO2008/121786, 2008, A1. Location in patent: Page/Page column 42-43

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