Background and overview[1]
P-Bromoacetophenone is an important organic synthesis intermediate and is widely used in the synthesis of medicines, pesticides, dyes, flavors and fragrances, perfumes, etc. At present, the main preparation methods for p-bromoacetophenone include Friedel-Crafts acylation method, 1-(4-bromophenyl) ethanol oxidation method and p-bromoethylbenzene oxidation method. Among them, the p-bromoethylbenzene oxidation method is divided into chemical oxidation method. Method and molecular oxygen oxidation method. Oxygen is a cheap, easy-to-obtain, clean, non-polluting and atom-economical oxidant. The method of directly oxidizing p-bromoethylbenzene to prepare p-bromoacetophenone with oxygen has significant advantages over other methods. sex. Studies have reported a method for catalyzing the oxygen oxidation of p-bromoethylbenzene to obtain p-bromoacetophenone using a perfluorinated substituted metal porphyrin/high-valent salt system. This method reacts for 24 hours under conditions of solvent-free, 1.5MPa, and 100°C. In the absence of high-valent metal salts, the chromatographic yield of p-bromoacetophenone is 22.5%; after adding K2Cr2O7, which seriously pollutes the environment, the chromatographic yield of p-bromoacetophenone is 22.5%. The chromatographic yield of acetophenone can be increased to 37.4%. The catalyst used is perfluoro-substituted metal porphyrin, and the dosage is 10-3mol/L (120ppm). The high-priced metal salts are mainly Na2MoO4, K2Cr2O7 and KMnO4, and the dosage is 1/800 of the mole number of ethylbenzene (1250ppm). The main disadvantages of this method are: (1) The catalytic activity of the perfluorinated metal porphyrin used in this method is low. Without adding high-valent metal salts, the yield of p-bromoacetophenone after reaction 24 is only 22.5 %. The reaction time is so long and the yield is so low, which not only consumes a lot of energy and resources, generates excessive operating costs, but also has extremely low production efficiency. (2) This method uses high-priced metal salts as cocatalysts in extremely large amounts (1250 ppm), which cause serious environmental pollution and are expensive. Therefore, a large amount of toxic and harmful wastewater and waste residue are generated during the production process. The high-priced metal salts used must be separated and recycled. Separation and recycling requires a large amount of energy. At the same time, the high-priced high-priced metal salts also greatly increase the production cost. (3) This method uses high-pressure (1.5MPa) reaction conditions, which causes equipment investment and operating costs to increase exponentially, and energy consumption is extremely high. In particular, it makes production potentially dangerous and safety is greatly reduced.
Preparation[1]
In a 100mL three-necked flask, add 18.531g p-bromoethylbenzene, 1ppm (0.07mg) tetraphenyliron porphyrin (that is, in formula (I), R11 is H, R12 is H, R13 is H, and M1 is Fe ), 10ppm (0.86mg) tetrakis-(p-chlorophenyl)cobalt porphyrin (i.e. R11 in formula (I) is H, R12 is H, R13 is Cl, M1 is Co), flow in at a flow rate of 40mL/min Oxygen initiates the reaction at 150°C and reacts at 100°C for 8 hours. The reaction mixture was frozen, centrifugally filtered, and then recrystallized with ethanol to obtain p-bromoacetophenone. The conversion rate of p-bromoethylbenzene was 79.8%, the yield of p-bromoacetophenone was 72.4%, and the purity was 99.5%.
Main reference materials
[1]CN201010103449.2 Method for preparing p-bromoacetophenone by bionic catalytic oxygen oxidation of p-bromoethylbenzene
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