Iodine → (2,5-Dimethylphenyl)boronic acid

関与物質

反応手順

Magnesium turnings (13.3 g; 0.55 mol) are introduced into a baked-out, argon-blanketed apparatus, covered with about 30 ml of THF and a few crystals of iodine are added. Without stirring, a few drops of bromo-p-xylene (cf. Example A1 a)) were subsequently added to the solution. The Grignard reaction began very quickly and the remaining bromo-p-xylene (total amount: 92.5 g; about 70 ml; 0.5 mol) was subsequently added dropwise while stirring. The mixture was refluxed for 4 hours and then cooled. The Grignard solution was then transferred in a countercurrent of protective gas into a 500 ml dropping funnel and added dropwise to a solution of trimethyl borate (62.4 g; 67 ml; 0.6 mol) in 350 ml of THF while stirring at −70° C. (time: about 1 hour). A precipitate was formed during this addition. The reaction mixture was allowed to warm to RT overnight and was then introduced while stirring into a mixture of 700 g of ice and 20 ml of concentrated sulfuric acid. The organic phase was separated off, the aqueous phase was extracted three times with chloroform and the combined organic phases were evaporated. The crude product was recrystallized from chloroform/hexane. This gave a colorless microcrystalline powder 47.71 g (64%).

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