Methyl isobutyryl acetate synthesis

Methyl isobutyryl acetate, with the chemical name Methyl Isobutyrylacetate, CAS number 42558-54-3, and methyl isobutyryl acetate formula C7H12O3, appears as a colorless to pale yellow liquid. Its density is 1.013 g/mL at 20°C, boiling point 55-57°C at 15 hPa, and melting point -75°C. This compound serves as an important intermediate in the synthesis of lipid-lowering statin drugs and is also used in the catalysis of butyl-4-methyl-3-oxo-pentanoate synthesis by immobilized Antarctic Candida lipase B.

Molecular Formula of Methyl Isobutyryl Acetate

Methyl isobutyryl acetate formula is C7H12O3, consisting of 7 carbon atoms, 12 hydrogen atoms, and 3 oxygen atoms. Its structure features a five-carbon chain with a methyl group (CH3) attached to the fourth carbon atom, a carbonyl group (C=O) on the third carbon, and an ester group (COOCH3) at the chain's end. Key characteristics include:

The presence of two methyl groups imparts strong lipophilicity to the compound, which may affect its interaction with cell membranes.

The carbonyl group contributes to the molecule's high reactivity, allowing it to participate in various chemical reactions.

Under specific conditions, the ester group can undergo hydrolysis.

Methyl Isobutyryl Acetate Synthesis

Method 1

Methyl isobutyryl acetate synthesis can be performed by reacting methyl isopropyl ketone with dimethyl carbonate. In this method, 10.00 grams (116.10 mmol) of methyl isopropyl ketone is slowly added to a suspension of sodium hydride (9.29 grams, 232.25 mmol) in 70 mL of 1,4-dioxane, and stirred at room temperature for 10 minutes. Then, 15.70 grams (174.31 mmol) of dimethyl carbonate is added and the mixture is stirred at 50°C for 3 hours. After the reaction, the mixture is cooled to room temperature, and 14 mL of acetic acid is added slowly. The precipitate is filtered and washed with 20 mL of 1,4-dioxane. Finally, the filtrate is concentrated under vacuum and purified by distillation to obtain methyl isobutyryl acetate with an 88% yield.

Method 2

Another method involves the reaction of methyl acetoacetate with isobutyryl chloride, requiring 1.05 moles of calcium hydroxide as an acid scavenger per mole of methyl acetoacetate. After the reaction, 1.05 moles of ammonium chloride (dissolved in 350 mL of water, with pH adjusted to 8.9-9.0 using ammonia solution and then to 0.5-1.0 with hydrochloric acid) is added. Although this synthesis method achieves a 78% yield with a product purity of 84% by gas chromatography, it generates a significant amount of wastewater and waste residue, which does not meet green production standards.

Method 3

In this method, diazonium and aldehyde condensation reactions are performed under a nitrogen atmosphere. Aldehyde (5.0 mmol) and diazoacetic ester (7.5 mmol) are refluxed in 10 mL of dichloroethane containing 50 mg of a Lewis acid catalyst (10% w/w of yttrium-zirconium oxide). After the specified treatment time, the yield of the product can reach 85%. However, obtaining the raw materials for this synthesis route can be challenging.

Method 4

Methyl isobutyryl acetate synthesis can also be achieved by preparing from α,β-unsaturated esters. At room temperature, a solution of Na2PdCl4 (0.2 mmol, 58 mg) is mixed with t-BuOOH (70% in t-BuOH, 1.5 mmol, 193 mg) and acetic acid solution (50% v/v, 1 mL), followed by the addition of acetone (1 mmol). The mixture is heated and stirred at 50°C for 1 to 5 hours. After completion, the mixture is poured into cold water, and extracted with dichloromethane. The combined extracts are washed with 3N-HCl and brine, and dried with magnesium sulfate. The solvent is removed, and the product is purified by column chromatography using ether-hexane to obtain the target ketone. This method uses expensive Na2PdCl4 and hazardous t-BuOOH, and the raw materials for α,β-unsaturated esters are difficult to obtain, making it unsuitable for industrial production.

Method 5

According to a report by Jiang Chengjun and colleagues, 74.0 grams (1.0 mol) of calcium hydroxide is added to 500 mL of dichloromethane. Under vigorous stirring at 20°C, 116 grams (1.0 mol) of methyl acetoacetate is added dropwise over 20 minutes. After adding 1.16 grams of 1,8-diazabicyclo[5.4.0]undec-7-ene, stirring is continued for 30 minutes. At 0°C, 288 grams (1.05 mol) of isobutyryl chloride is added dropwise to the solution obtained. After the addition, the temperature is raised to 30°C and maintained for 8 hours, then cooled to 25°C. Water is added, and the pH is adjusted to 3 with hydrochloric acid. The mixture is allowed to separate into layers, and the organic phase is recovered by rotary evaporation to obtain methyl isobutyryl acetate. The yield is 129.6 grams of methyl isobutyryl acetate with a GC purity of 95.3%.

References

• Zhejiang Jiangbei Pharmaceutical Co., Ltd. Synthesis unit of statin intermediate methyl isobutyryl acetate. 2022-09-20.
• Zhejiang University of Science and Technology. A method for preparing methyl isobutyrylacetate. 2022-10-28.
• https://pubchem.ncbi.nlm.nih.gov/compound/2759969