Pinacol → 1-(tetrahydro-2H-pyran-2-yl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

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Reaction Steps

To a 500 ml flask was added 1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazole 14.1.A and 100 ml of THF. The solution was cooled to −78° C. at which time butyllithium (52 ml, 83 mmole, 1.6M in hexanes) and pinacol (9.8 g, 83 mmole) were added. The reaction was stirred for 5 minutes at −78 C and then triisopropyl borate (19 g, 103 mmole) was added. The reaction was slowly warmed to room temperature over 90 minutes and then stirred at room temperature for an additional 16 hours at which time the reaction was quenched with NH4Cl aq. (pH ˜7-8), extracted with EtOAc, and purified by silica gel chromatography to give 1-(tetrahydro-2H-pyran-2-yl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole 14.1.B (7.2 g, 38% yield).

Provenance & Evidence