Cesium carbonate → 1-(2-Methoxyethyl)-1H-pyrazole-4-boronic acid, pinacol ester

HRID 1925125Notes

Reaction equation

HRID 1925125 reaction equation
[CH3:1][C:2]1([CH3:14])[C:6]([CH3:8])([CH3:7])[O:5][B:4]([C:9]2[CH:10]=[N:11][NH:12][CH:13]=2)[O:3]1.C(=O)([O-])[O-].[Cs+].[Cs+].Br[CH2:22][CH2:23][O:24][CH3:25]>CN(C=O)C.O>[CH3:25][O:24][CH2:23][CH2:22][N:12]1[CH:13]=[C:9]([B:4]2[O:5][C:6]([CH3:7])([CH3:8])[C:2]([CH3:14])([CH3:1])[O:3]2)[CH:10]=[N:11]1

Participants

6

Reactant 3

HCID 10796Cesium carbonateHCID 809722-Bromoethyl methyl ether2×HCID 27740104-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

Product 1

HCID 112304911-(2-Methoxyethyl)-1H-pyrazole-4-boronic acid, pinacol esterYield 116.1%

Reagents, catalysts & solvents 2

HCID 962WaterSolventHCID 6228DimethylformamideSolvent

Procedure

A solution of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (0.8 g, 4.1 mmol), cesium carbonate (2.0 g, 6.2 mmol), and 1-bromo-2-methoxyethane (0.41 mL, 4.3 mmol) in DMF (14 mL) was heated in a microwave at 90° C. for 1 hr. After the initial heating, additional 1-bromo-2-methoxyethane (0.41 mL) was added to the reaction. Heating was repeated for an additional 1 hr. The crude reaction mixtures were then diluted with water (250 mL) and extracted with ethyl acetate (3×50 mL). Product was purified by silica gel column using DCM/EtOAc/MeOH (8/1.5/0.5) as eluent to give 1-(2-methoxyethyl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (1.2 g) as a light yellow oil. ESI-MS:m/z 253.2 (M+H)+.

Workup

  1. temperatureAfter the initial heating
  2. temperatureHeating
  3. customThe crude reaction mixtures
  4. extractionextracted with ethyl acetate (3×50 mL)
  5. customProduct was purified by silica gel column

Sources & evidence

ORD record
ord-fcf01e03ae3e48dc97ee67bc2cb08cda
Source dataset
uspto-grants-2012_05
Patent number
US08178534B2

Reaction notes

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