6948-34-1

General procedure for the synthesis of 6-methylthiobenzodihydropyran-4-one from 3-[(4-methylphenyl)thio]propionic acid: 20 g (0.1 mol) of 3-[(4-methylphenyl)thio]propionic acid was dissolved in a 1000 ml beaker containing 70 ml of concentrated sulphuric acid, and the reaction was carried out for 12 h at room temperature. Upon completion of the reaction, the reaction mixture was cooled in an ice-water bath to precipitate a large amount of yellow solid precipitate, which was subsequently filtered. The filter cake was washed sequentially with 5% sodium bicarbonate solution and distilled water until neutral. The crude product was purified by recrystallization from 50% ethanol solution to give 16.88 g of light yellow solid 6-methylthiobenzodihydropyran-4-one in 93% yield.

[1] Letters in Organic Chemistry, 2016, vol. 13, # 3, p. 206 - 216
[2] Journal of Chemical Research, 2004, # 6, p. 394 - 395
[3] Bioorganic and Medicinal Chemistry, 2009, vol. 17, # 13, p. 4569 - 4574
[4] Chinese Journal of Chemistry, 2011, vol. 29, # 4, p. 757 - 764
[5] Chemische Berichte, 1923, vol. 56, p. 1275