CAS 924-50-5 | Methyl 3-methyl-2-butenoate

Introduction
Methyl methacrylate is an important intermediate in the production of chrysanthemic acid by Martel method.

Specification of CAS 924-50-5 | Methyl 3-methyl-2-butenoate

Synthesis of CAS 924-50-5 | Methyl 3-methyl-2-butenoate

Its preparation method is to use diacetone (1mol) and sodium hypochlorite solution (500mL) to vigorously stir in a reaction flask, the reaction is exothermic, the temperature is raised to 50 ℃ and the sodium hypochlorite (150mL, the total amount is 5mol) is continuously added dropwise, and the rate of addition is controlled, The reaction temperature was maintained at 55-60°C. When the sodium hypochlorite was added, the temperature was raised to about 65°C, and then continued stirring for 3-4 hours under natural cooling. A small amount of Na2SO3 was added to reduce the excess sodium hypochlorite, and then the mixture was left to separate the layers. Chloroform.

Acidified with dilute H2SO4 at 20°C, extracted with chloroform, washed with water, dried, evaporated the solvent chloroform, and the residue was cooled to obtain a yellow solid, that is, isopentonic acid (CAS[541-47-9]), m.p.60～65 ℃ (literature value m.p.68.5～69.5℃), b.p.194～195℃.

Mix 1 mol of the above-prepared prenyl acid with 4.4 mol of methanol, add a little concentrated sulfuric acid as a catalyst, stir at 60-70 ° C for 5 h, cool and dilute with water to separate the organic layer, extract the aqueous layer with chloroform, and mix with the organic layer. Combined, washed with dilute Na2CO3 solution, washed with water, dried, evaporated chloroform, and collected the fractions at 130-140°C as methyl prenyl.

In addition, isobutylene and carbon tetrachloride are used to pressurize the telomerization reaction in the presence of copper catalyst, and then hydrolyzed with sulfuric acid to obtain prenyl acid. Prenyl esters were obtained. Trialkyl phosphite can also be reacted with ethyl chloroacetate to generate ethyl acetate dialkyl phosphite, and then in polar solvent, in the presence of strong base (such as sodium hydride, sodium amide, sodium alkoxide), etc. with acetone. The Wadsovorth-Emmons reaction was carried out to obtain prenyl ester (the yield in the first step was 90%, and the yield in the second step was 84.5%).

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