关键词: 自由基Brook重排, 烯烃双官能团化, 三组分反应, 锰催化

Incorporation of fluorine has always been a conventional strategy for designing new drugs and materials because it can usually improve the physiochemical and physiological properties of organic molecules. Among various organofluorine compounds, α-fluoroalkyl alcohols are of particular importance and they are important skeletons of bioactive molecules. Herein, we report a three components olefin difunctionalization reaction for the synthesis of α-fluoroalkyl alcohols through manganese-catalyzed radical Brook rearrangement of α-fluoroalkyl-α-silyl methanols. The operationally simple reaction showed broad substrate scope, and the product could be prepared on gram scale. Twenty-five α-fluoroalkyl alcohols have been synthesized in 44%~86% yields. It is compatible with a variety of halogen substituents (F, Cl, Br), electron donating OMe and naphthalenyl groups and is also suitable for different symmetrical aryl olefins, asymmetric aryl olefins and alkoxyl olefins. The reaction is also compatible with different nucleophiles such as aryl carboxylic acids and anilines. Besides, the reaction is compatible with a α-alkyl alcohol which afford the desired olefin difunctionalization product in 36% yield. A representative procedure is described as follows. In the glovebox, α-difluoromethyl-α-dimethylphenylsilyl methanol (64.8 mg, 0.3 mmol), 1,1-stilbene (223 mg, 0.3 mmol), benzoic acid (110 mg, 0.9 mmol), Mn(OAc)₂ (2.6 mg, 0.015 mmol), tert-butyl peroxybenzoate (TBPB, 175 mg, 0.9 mmol), 4Å MS (30 mg) and dry dichloromethane (DCM, 0.5 mL) were added to a dry 10 mL reaction tube equipped with a magnetic agitator. The reaction mixture was then removed from the glove box, stirred at 70 ℃ for 1 h. Then tetrabutylammonium fluoride (TBAF, 0.36 mmol) was added at 0 ℃. After 30 min, the reaction mixture was quenched with saturated sodium bicarbonate aqueous solution (10 mL), extracted with ethyl acetate (10 mL×3). The organic phase was combined, washed with saturated NaCl aqueous solution and dried with anhydrous sodium sulfate and concentrated under vacuum. Then the crude product was purified by silica gel column chromatography to obtain corresponding target product.

Key words: radical Brook rearrangement, olefin difunctionalization, three component reaction, Mn-catalysis