Benzene → 1-Methylethyl (2E)-2-butenoate
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[C:1]([OH:6])(=[O:5])/[CH:2]=[CH:3]/[CH3:4].[CH:7](O)([CH3:9])[CH3:8].C1C=CC=CC=1.OS(O)(=O)=O>C1(C)C=CC(S(O)(=O)=O)=CC=1.CCOCC.O>[CH:7]([O:5][C:1](=[O:6])/[CH:2]=[CH:3]/[CH3:4])([CH3:9])[CH3:8][C:1]([OH:6])(=[O:5])/[CH:2]=[CH:3]/[CH3:4].[CH:7](O)([CH3:9])[CH3:8].C1C=CC=CC=1.OS(O)(=O)=O>C1(C)C=CC(S(O)(=O)=O)=CC=1.CCOCC.O>[CH:7]([O:5][C:1](=[O:6])/[CH:2]=[CH:3]/[CH3:4])([CH3:9])[CH3:8]40.0 g (465 mmol) of crotonic acid (Fluka 28010), 25.1 g (418 mmol) of isopropanol (Merck 1.09634.2500), 200 mL of benzene, 4.2 g of conc. H2SO4 and 2.1 g of para-toluene sulfonic acid was charged to a 500 mL flask equipped with a magnetic stirrer bar and Dean-Stark water separator. The mixture was refluxed until water formation ceased. 200 mL of ether was added to the mixture, and then washed with several portions of NaHCO3 (aq., sat.) until the the acid was neutralized. Organic phase was separated, dried with MgSO4 and filtered. Solvent was removed under reduced pressure and the remainder distilled at 95° C. to give 30.5 g of isopropylcrotonate. Yield 57%. 1H-NMR (CDCl3): 6.95 (dq, 1H), 5.82 (d, 1H), 5.05 (sept, 1H), 1.88 (d, 3H), 1.25 (d, 6H).
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