[S:1]1[CH:5]=[CH:4][CH:3]=[CH:2]1.[C:6](O)(=[O:10])[CH:7]([CH3:9])[CH3:8]>O>[CH3:8][CH:7]([CH3:9])[C:6]([C:2]1[S:1][CH:5]=[CH:4][CH:3]=1)=[O:10]A mixture containing thiophene (10.1 g, 120 mmol), isobutyric acid (8.8 g, 100 mmol) and 20 g of polyphosphoric acid was magnetically stirred at 75° C. for 2 hours. The reaction mixture was diluted with water (100 ml) and extracted with CH2Cl2 (2×). The combined organic extracts were washed with water, brine, dried (Na2SO4), filtered and concentrated under reduced pressure to yield a brown oil: 14 g (77%) GC-MS: M=154.0.
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