Diethyl Ether → 1-ethyl-4-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

HRID 2392256Notes

Reaction equation

HRID 2392256 reaction equation
[CH3:1][CH2:2]OCC.[CH3:6][C:7]1[CH:8]=[N:9][NH:10][CH:11]=1.[Li]CCCC.C(O[B:21]1[O:25][C:24]([CH3:27])([CH3:26])[C:23]([CH3:29])([CH3:28])[O:22]1)(C)C>[NH4+].[Cl-]>[CH2:1]([N:9]1[C:8]([B:21]2[O:25][C:24]([CH3:27])([CH3:26])[C:23]([CH3:29])([CH3:28])[O:22]2)=[C:7]([CH3:6])[CH:11]=[N:10]1)[CH3:2]

Participants

6

Reactant 4

HCID 3283Diethyl EtherHCID 34064-MethylpyrazoleHCID 50177412-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolaneHCID 178418339Butyllithium

Product 1

HCID 578269151-ethyl-4-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazoleYield 80%

Reagents, catalysts & solvents 1

HCID 25517Ammonium ChlorideSolvent

Procedure

At 0° C., to the above ether solution of 4-methylpyrazole was added n-BuLi (36.4 mL, 2.5 M in Hexane, 91 mmol) dropwise. The reaction solution was stirred for 1 hour at RT and then cooled to −78° C. [J. Heterocyclic Chem. 41, 931 (2004)]. To the reaction solution was added 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (18.49 g, 99 mmol). After 15 min at −78° C., the reaction was allowed to warm to 0° C. over 1 hour. The reaction was diluted with saturated NH4Cl solution and extracted with DCM. The organics were dried over Na2SO4 and concentrated under vacuum to afford 1-ethyl-4-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (16 g, 80% purity) as a syrup which was used without further purification: LC-MS (ES) m/z 155 (M+H)+ for [RB(OH)2].

Workup

  1. waitAfter 15 min at −78° C.
  2. temperatureto warm to 0° C. over 1 hour
  3. extractionextracted with DCM
  4. dry with materialThe organics were dried over Na2SO4
  5. concentrationconcentrated under vacuum

Sources & evidence

ORD record
ord-543a2c9accdc427194210e67e88f94e9
Source dataset
uspto-grants-2012_09
Patent number
US08273782B2

Reaction notes

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