1H-Pyrazole, 1-methyl- → 1-methyl-5-(tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

HRID 1967087Notes

Reaction equation

HRID 1967087 reaction equation
[CH3:1][N:2]1[CH:6]=[CH:5][CH:4]=[N:3]1.[Li]CCCC.C(O[B:16]1[O:20][C:19]([CH3:22])([CH3:21])[C:18]([CH3:24])([CH3:23])[O:17]1)(C)C>C1COCC1.[NH4+].[Cl-]>[CH3:1][N:2]1[C:6]([B:16]2[O:20][C:19]([CH3:22])([CH3:21])[C:18]([CH3:24])([CH3:23])[O:17]2)=[CH:5][CH:4]=[N:3]1

Participants

6

Reactant 3

HCID 702551H-Pyrazole, 1-methyl-HCID 50177412-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolaneHCID 178418339Butyllithium

Product 1

HCID 49129081-methyl-5-(tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazoleYield 76.9%

Reagents, catalysts & solvents 2

HCID 8028TetrahydrofuranSolventHCID 25517Ammonium ChlorideSolvent

Procedure

To a solution of 1-methylpyrazole (4.1 g, 50 mmole) in THF (100 mL) at 0° C. was added n-BuLi (2.2M in THF, 55 mmole). 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 (12.3 mL, 60 mmole). 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 a tan solid (8.0 g, 76%) which was used without further purification. LCMS (ES) m/z 127 (M+H)+ for [RB(OH)2]; 1H NMR (CDCl3, 400 MHz) δ 7.57 (s, 1H), 6.75 (s, 1H), 4.16 (s, 3H), and 1.41 (s, 12H).

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-f44421f1da014f25a273a88901fdb64b
Source dataset
uspto-grants-2013_04
Patent number
US08420690B2

Reaction notes

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