关键词: α,α-二溴甲基酮, α,α-二氯甲基酮, 选择性脱卤, 有机电化学合成

The regulation of reaction to efficient and highly selective transformation into distinct valuable molecules separately from the same materials is a remarkable fundamental process in organic synthesis. Selective halogenation and dehalogenation could greatly benefit as organohalogen compounds are versatile building blocks, key intermediates and pharmaceutically essential molecules. α,α-Dihalomethyl ketones have many unique biological and organic synthetic properties. They are valuable structural frameworks in natural products, pharmaceuticals, agrochemicals and organic synthesis. α,α-Dihalomethyl ketones are one of the most important intermediates in organic synthesis. Electrochemistry has become a powerful tool in organic synthesis to avoid the use of expensive and toxic oxidants or reductants to reduce the production of harmful and toxic by-products. Therefore, in this paper, the selective dehalogenation of α,α,α-trihalogen (chloro, bromo) methyl ketones under electrochemical conditions was studied, and 17 kinds of α,α-dibromomethyl ketones and 17 kinds of α,α-dichloromethyl ketones were prepared with the highest yield of 92%. The reaction has the advantages of mild conditions, simple operation and high tolerance of functional groups. The typical procedure is as follows: the electrolysis was carried out in an undivided electrolytic cell, with a platinum anode (10 mm×10 mm×0.2 mm), and a platinum cathode (10 mm×10 mm×0.2 mm). α,α,α-Trihalomethyl ketones (0.5 mmol, 1.0 equiv.) and electrolyte (n-Bu₄NHSO₄ or tetrabutylammonium fluoride, 0.25 mmol, 0.5 equiv.) were dissolved in 5 mL solvent (ClCH₂CH₂Cl or CH₃CN). The reaction mixture was electrolyzed under a constant current of 10 mA and at room temperature until the complete consumption of starting material as monitored by TLC or NMR. After the reaction, EtOAc (10 mL×3) was added, and then washed with water (10 mL×3) and then with brine (10 mL). The organic fraction was dried and concentrated with anhydrous MgSO₄. The residue was purified by silica gel chromatography to give the dehalogenated product.

Key words: α,α-dibromomethyl ketones, α,α-dichloromethyl ketones, selective dehalogenation, organic electrosynthesis