2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → 4,4,5,5-Tetramethyl-2-(3-methylbut-1-yn-1-yl)-1,3,2-dioxaborolane

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of Ia (7.0 g, 50 mmol) in dry THF (25 mL) at −78° C. was added n-BuLi (1.6 M in n-hexane, 62.5 mL, 100 mmol). After being stirred for 1 hour at −78° C., the reaction mixture was warmed to room temperature and stirred for 1 hour at that temperature. Another flask was charged with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7.8 mL, 38 mmol) in dry THF (50 mL) under argon atmosphere, and the reaction mixture was cooled to −78° C. The lithium acetylide from the first flask, which was cooled to −78° C., was slowly added to the second by a double-ended needle. The mixture was stirred at −78° C. for 2 hours, after which anhydrous HCI (100 mmol) was added. Then, reaction mixture was warmed to room temperature. After removal of the precipitated LiCI by filtration and removal of solvents under reduced pressure, the residue was purified by distillation (113-115° C./7 mbar) to afford IIIa (5.9 g, 80%) as an oil.

Provenance & Evidence