ChemicalBook CAS DataBase List 1,3,5-TRIMETHYL-4-(4,4,5,5-TETRAMETHYL-1,3,2-DIOXABOROLAN-2-YL)-1H-PYRAZOLE

1,3,5-TRIMETHYL-4-(4,4,5,5-TETRAMETHYL-1,3,2-DIOXABOROLAN-2-YL)-1H-PYRAZOLE synthesis

6synthesis methods

Product Name:1,3,5-TRIMETHYL-4-(4,4,5,5-TETRAMETHYL-1,3,2-DIOXABOROLAN-2-YL)-1H-PYRAZOLE
CAS Number:844891-04-9
Molecular formula:C12H21BN2O2
Molecular Weight:236.12

61676-62-8 Synthesis

2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

61676-62-8
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1,3,5-TRIMETHYL-4-(4,4,5,5-TETRAMETHYL-1,3,2-DIOXABOROLAN-2-YL)-1H-PYRAZOLE

844891-04-9
152 suppliers
$7.00/250mg

Yield: 77%

Reaction Conditions:

Stage #1:4-bromo-1,3,5-trimethylpyrazole with n-butyllithium in tetrahydrofuran;hexane at -78 - 40; for 0.333333 h;
Stage #2:2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane in tetrahydrofuran;hexane at -78 - 40;

Steps:

21.21A
Example 21; 1,3,5-Trimethyl-4-{4-[3-(2-methyl-pyrrolidin-1-yl)-trans-cyclobutyl]-phenyl}-1H-pyrazole; Example 21A; 1,3,5-Trimethyl-4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-pyrazole; A solution of 4-bromo-1,3,5-trimethyl-1H-pyrazole (1 g, 5.3 mmol) in anhydrous THF (20 mL) cooled to -78° C. under a nitrogen atmosphere was treated dropwise with n-butyl lithium (4.2 mL, 1.6 M in hexane) and stirred at room temperature for 20 minutes. Then, 2-isopropoxy-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane (1.7 mL, 8.3 mmol) was added dropwise at -78° C. and allowed to warm to ambient temperature overnight. Ethyl acetate was added and the mixture was filtered through diatomaceous earth. The filtrate was concentrated and chromatographed on silica gel eluting with 40% ethyl acetate in hexanes to provide the title compound as white crystals (996 mg, 77%). ¹H NMR (300 MHz, CDCl₃) δ 1.29 (s, 12H), 2.33 (s, 3H), 2.37 (s, 3H), 3.69 (s, 3H); (DCl/NH₃) m/z 237 (M+H)⁺.

References:

Liu, Huaqing;Hancock, Arthur A.;Cowart, Marlon D.;Hancock, Kathryn J. US2007/78133, 2007, A1 Location in patent:Page/Page column 29-30