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

Participants

Reaction Conditions

Reaction Steps

A solution of 100 g of 2-methylthiophene (1.02 mol) and 104 ml of methacrylic acid (1.22 mol) in 200 ml of dichloromethane was added dropwise within 30 minutes at 80° C. to 1000 g of super-PPA. Afterwards, the reaction mixture was stirred at 80° C. for 3 hours. The dark red mixture was poured into 1000 g of crushed ice and stirred until the polyphosphoric acid had completely dissolved. The aqueous phase was extracted twice with 400 ml each time of a dichloromethane/hexane solvent mixture (30 parts by volume/70 parts by volume). The combined organic phases were washed with a saturated aqueous solution of sodium hydrogencarbonate and dried over magnesium sulfate. After removal of the solvents on a rotary evaporator, 136 g of crude product were obtained. The distillation of the crude product (90° C., 0.1 torr) gave 76 g (46%) of product.

Provenance & Evidence