2-Methylpentan-3-ol → But-2-enoic acid 1-ethyl-2-methyl-propyl ester

Reaction equation

[CH3:1][CH:2]([CH:4]([OH:7])[CH2:5][CH3:6])[CH3:3].[C:8](O)(=[O:12])/[CH:9]=[CH:10]/[CH3:11]>C1(C)C=CC(S(O)(=O)=O)=CC=1.C1(C)C=CC=CC=1>[CH2:5]([CH:4]([O:7][C:8](=[O:12])[CH:9]=[CH:10][CH3:11])[CH:2]([CH3:3])[CH3:1])[CH3:6]

Participants

Procedure

A reaction flask was charged with ethylmagnesium chloride (CH3CH2MgCl) (2 M, 2.17 L) and cooled to −10° C. Isobutyraldehyde ((CH3)2CHCHO) (295 g) was fed over about 1 hour while the temperature was kept under 15° C. The reaction mixture was aged to room temperature over about 6 hours and then poured into a mixture of ice and acetic acid (CH3COOH) (293 g). Hexanes (C6H14) (350 mL) were added and aqueous and organic layers were split. The organic layer was separated, washed sequentially with sodium bicarbonate (NaHCO3), brine, and water, and further distilled to provide 2-methyl-pentan-3-ol (336 g). 2-Methyl-pentan-3-ol (250 g), crotonic acid (CH3CH═CHCOOH) (198 g), toluene (250 mL), and para-toluenesulfonic acid (PTSA) (10 g) were then charged into to 2-L reaction flask fitted with a Bidwell-Sterling trap. The reaction mixture was heated to reflux. Water was collected and removed via the Bidwell-Sterling trap. The reaction mixture was aged at reflux for about 22-30 hours till the Gas Chromatography (“GC”) analysis showed completion of the reaction. The resulting reaction mixture was washed sequentially with brine, sodium carbonate (Na2CO3), and brine, and further purified by fractional distillation to provide but-2-enoic acid 1-ethyl-2-methyl-propyl ester (311 g) with a boiling point of 65° C. at 0.6 mmHg.