Water → 4,5-Dihydro-2,5-dimethyl-6H-cyclopenta[b]thiophen-6-one

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Reaction Steps

A mixture of 150 g of 2-methylthiophene (1.5 mol) and 157.5 g of methacrylic acid (1.8 mol) was added within 30 minutes at about 80° C. to 1500 ml of Eaton's reagent, and the temperature was between 78° C. and 83° C. On completion of addition, the reaction mixture was stirred for a further 5 minutes and then gradually poured into a vigorously stirred mixture of 3000 ml of water and 500 ml of dichloromethane. The organic phase was removed and dried over magnesium sulfate. The solvent was distilled off on a rotary evaporator and 263.5 g of crude product were obtained in a purity of 88.2% according to GC-MS analysis. A portion of the crude product (79 g) was distilled (92° C., 0.02 torr). 56.5 g (76%) of product were obtained as a mixture of two isomers in a ratio of approx. 9:1 (thiophen-6-one: thiophen-4-one).

Provenance & Evidence