1,2-Dibromoethane → 4-Formylphenylboronic Acid

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Reaction Steps

Under an argon atmosphere, 3.65 g of magnesium turnings are covered with 15 ml of anhydrous THF and treated with 0.5 ml of 1,2-dibromoethane. Gentle warming leads to a vigorous reaction. After the reaction has subsided, the solvent is pipetted off with a pipette, treated with 40 ml of anhydrous THF and 1/3 of a solution of 32 g of the product 1a) in 30 ml of anhydrous THF are added. The reaction is started with Red-Al and by warming. The remainder of the product from 1a) is then added dropwise within the course of 35 min. After dropwise addition is complete, the mixture is boiled under reflux for a further 1 h. The Grignard product is then added dropwise to a solution, cooled to -68° C., of 33.5 ml of tributyl borate under an argon atmosphere in 50 ml of THF. After 30 min, the cooling is removed. The mixture is then stirred at RT for 1 h. It is then concentrated, the honey-colored oil is taken up in 100 ml of ether and 80 ml of Ace-cold H2SO4 (1M) are added. The ether phase is separated off and extracted twice more with 50 ml of ether, concentrated and 30% strength (6N) KOH is added until an alkaline reaction (pH 14) occurs. 70 ml of H2O are added and the butanol is removed azeotropically at 35°-40° C. in a high vacuum. This process is repeated again with 50 ml of H2O. The residue is rendered acidic with 1M H2SO4 (pH 1) and boiled for 30 min. The title compound is obtained as a pale yellow solid by filtration. m.p.=255°-260° C.

Provenance & Evidence