3-ETHYL-4-METHYLPENTANOIC ACID synthesis

Yield:60308-89-6 2.6 g

Reaction Conditions:

Stage #1: n-butyl magnesium bromide;propenewith triisopropyl phosphite;tantalum pentachloride in tetrahydrofuran;diethyl ether at -68 - 20; for 7 h;Inert atmosphere;Autoclave;
Stage #2: carbon dioxide in tetrahydrofuran;diethyl ether at 0; for 3 h;Inert atmosphere;Autoclave;

Steps:

For this, a solution n-BuMgBr (50 mL, 25 mmol, 0.5 mM, THF-Et2O, 1:1) was cooled to -68°C in a glass flask under dry Ar, treated with propylene (20 mmol, 1.2 mL) cooled to -68°C and catalyst consisting of TaCl5 (1 mmol, 0.36 g) and (i-PrO)3P (1 mmol, 0.21 g), stirred for 5 min, transferred to a Midiclave autoclave (0.1 L, Buchi), and stirred at room temperature (20°C) for 7 h. The resulting mixture in the glass flask was purged slowly at 0°C with CO2 for 3 h and then treated with aqueous HCl solution (10%, 20 mL). The resulting carboxylic acid 3 was extracted with Et2O (3 × 50 mL) and dried over anhydrous MgSO4. The solvents were evaporated. The residue was separated by column chromatography over SiO2 (60-200 μm, petroleum ether-t-butylether, 5:1) to produce 3-ethyl-4-methylpentanoic acid (3, 2.6 g) with the following spectral characteristics. IR spectrum (ν, cm-1): 1710. 1 NMR spectrum (δ, ppm): 0.86-0.91 (9, m), 0.98-1.02 (2, m), 1.61-1.66 (2, m),1.61-1.66 (1, m), 1.80-1.87 (1, m), 2.25-2.41 (2, m), 11.31 (1, s). 13C NMR spectrum (δ, ppm): 178.90, 43.86, 39.25,29.91, 23.65, 19.03, 18.65, 12.93.

References:

Sultanov;Khafizov, F. Sh.;Khafizov;Ozden [Chemistry of Natural Compounds,2019,vol. 55,# 5,p. 987 - 988][Khim. Prir. Soedin.,2019,# 5,p. 849 - 850,2]