Background and overview[1]
Substituted benzoic acid 3,4-difluorobenzoic acid is an organic synthesis intermediate that can be focused on development. It can be used in the production of organic chemical raw materials and various pesticides. It is also a synthetic intermediate for dyes, pesticides and medicines. 3,4-Difluorobenzoic acid is a raw material for preservatives and fragrances. It can also be used in liquid crystal materials. It has the advantages of high value and good market prospects.
Preparation[1-2]
Method 1. Add Wittig reagent 3,416mg (1mmol) of 4-difluorophenylformylmethylene triphenylphosphine into a dry 100mL round-bottomed flask, add 30ml of THF, 1ml (9mmol) of 30% peroxide Hydrogen solution, react under nitrogen protection at 50°C. After 12 hours, the raw material Wittig reagent reacted almost completely. After the reaction is completed, most of the solvent is removed by rotary evaporation, 10 mL each of dichloromethane and water are added, and liquid separation extraction is performed. The organic phase was dried by adding anhydrous sodium sulfate and concentrated. The crude product was isolated to obtain a light yellow solid, 134 mg, and the product was 85%. 1HNMR (MHz, DMSO) δ7.88-7.82 (1H, m), 7.80-7.75 (1H, m), 7.56-7.49 (1H, m).
Method 2: Add 4,5-difluorophthalic anhydride (0.5g, 2.7mmol) and copper oxide (5 wt% of starting material) to 5ml of N-methyl-2-pyrrolidone slurry , n-tridecane (0.25 g) was added as an internal standard. The mixture was heated to 190°C for 3 hours. When GC analysis showed that the raw material had been completely consumed, the raw material was converted into 3,4-difluorobenzoic acid with a yield of 85% based on the internal standard.
References
[1]CN201710548995.9 A new method for the metal-free catalytic oxidation synthesis of substituted benzoic acid compounds
[2]US4937377
