Preparation method of 2, 2-dimethyl cyclopentanone

Abstract

The invention discloses a preparation method of 2, 2-dimethyl cyclopentanone, which comprises the following steps: methylating 2-methoxycarbonyl cyclopentanone to obtain a methylated product 2-methyl-2-methoxycarbonyl cyclopentanone, carrying out keto-carbonyl protection on the methylated product to obtain a protected product 2-methyl-2-methoxycarbonyl cyclopentanone ketal, carrying out ester group reduction on the protection product to obtain an alcohol product 2-hydroxymethyl-2-methyl cyclopentanone ketal, carrying out deprotection on the alcohol product under an acidic condition to obtain a deprotection product 2-hydroxymethyl-2-methyl cyclopentanone, and brominating the deprotection product to obtain 2-bromomethyl-2-methyl cyclopentanone. All raw materials adopted by the method are low in cost and easy to obtain in the market, and reactions in all steps are conventional reactions and easy to implement; the process is simple, mild in reaction condition and easy to operate; the reaction time is short, control is easy, the yield of each step is 90% or above, and industrial large-scale production is easy to achieve.

Description

technical field [0001] The invention relates to the technical field of organic intermediates, in particular to a preparation method of 2,2-dimethylcyclopentanone. Background technique [0002] Meconazole, chemical name (1RS,5RS; 1RS,5SR)-5-(4-chlorobenzyl)-2,2-dimethyl-1-(1H-1,2,4,-triazole -1-methyl)cyclopentanol. It is a new type of triazole fungicide developed by Kureha Chemical Company in Japan in the early 1990s and jointly developed with Nitrile Ammonium Corporation (now BASF) of the United States. It has the same antibacterial spectrum as other triazole fungicides. It has the characteristics of strong systemic absorption and excellent activity. The main mechanism of action is to inhibit the C-14 demethylation reaction, hinder the synthesis of sterols, thereby destroying the synthesis function of bacteria, and belongs to the inhibitor of C-14 demethylase. Field application of metconazole has excellent effects on the plant diseases of Septoria, Fusarium and Puccinia ...

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Problems solved by technology

[0004] Among the various synthetic routes of metconazole that have been reported, whether it is 2,2-dimethyl-5-(4-chlorobenzyl)cyclopentanone or 5-(4-chlorobenzylidene)- 2,2-Dimethylcyclopentanone is the key intermediate to prepare metconazole, the intermediate 2,2-dimethylcyclopentanone will be used directly, but the industrialization of 2,2-dimethylcyclopentanone The preparation method is rarely reported. Li Bolin et al. reported the synthesis process of the compound 2,2-dimethylcyclopentanone in "Popular Science and Technology" 2019, 21, 42-43. The author started with dimethyl adipate as the raw material. After condensation, methylation and decarboxylation, 2-methylcyclopentanone is obtained, and 2-methylcyclopentanone is reacted with dimethyl sulfate to obtain 2,2-dimethylcyclopentanone. The obvious disadvantage of this process route When the second methyl group is on the 2-position, it is very easy to produce mono- or polymethylated products at the 5-position, and the reaction conditions are difficult to control for methylation at the 2-position, which leads to low yield and is difficult to realize industrial production ; Seb Caille et al. in J. Org. Chem. 2011, 76 , 5198-5206 reported that isopropyl cyanide was used as the starting material, reacted with 1-bromo-3-chloropropane at -70 ° C, and then carried out halogen exchange with sodium iodide, and finally reacted with n-butyl at -20 ° C Lithium-based reaction, the final product 2,2-dimethylcyclopentanone was obtained with a yield of 32%. Although the reaction route of this method is relatively short, the first and third steps need to be heated at -70°C and -20°C respectively. Under low temperature conditions, and the yield of the last step is very low, it is difficult to realize industrial production

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