ChemicalBook CAS DataBase List 1-Methyl-1H-pyrazole-5-boronic acid pinacol ester

1-Methyl-1H-pyrazole-5-boronic acid pinacol ester synthesis

5synthesis methods

Product Name:1-Methyl-1H-pyrazole-5-boronic acid pinacol ester
CAS Number:847818-74-0
Molecular formula:C10H17BN2O2
Molecular Weight:208.07

930-36-9 Synthesis

930-36-9
335 suppliers
$5.00/1g

61676-62-8 Synthesis

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

61676-62-8
322 suppliers
$10.00/5g

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

847818-74-0
267 suppliers
$6.00/1g

Yield:847818-74-0 77%

Reaction Conditions:

Stage #1:1-methyl-1H-pyrazole with n-butyllithium in tetrahydrofuran at 0 - 20; for 1 h;
Stage #2:2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane in tetrahydrofuran at -78 - 0; for 1.25 h;
Stage #3: with ammonium chloride in tetrahydrofuran

Steps:

2
To a solution of 1-methyl pyrazole (4.1 g, 50 mmole) in THF (100 mL) at 0⁰C 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 0⁰C over 1 hour. The reaction was diluted with saturated NH₄CI solution and extracted with DCM. The organic fractions were washed with H₂O (2 x 100 ml_), dried over Na₂SO₄ and concentrated under vacuum to afford a tan solid (8.0 g, 77%) which was used without further purification. LCMS (ES) m/z 127 (M+H)⁺ for [RB(OH)₂]; ¹H NMR (CDCI₃, 400 MHz) δ 7.57 (s, 1 H), 6.75 (s, 1 H), 4.16 (s, 3H), and 1.41 (s, 12H).