75860-79-6

56844-38-3

General procedure for the synthesis of 2,4-dichloro-5-methylthieno[2,3-d]pyrimidine from 5-methyl-thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione: 3.0 g of 5-methyl-thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione was dissolved in 20 mL of phosphorus trichloride (POCl3), and subsequently 0.8 mL of N,N-dimethylaniline as a catalyst. The reaction mixture was heated under reflux conditions for 16 hours. Upon completion of the reaction, the excess POCl3 was removed by distillation under reduced pressure.The residue was slowly poured into ice water and precipitate was precipitated. The precipitate was collected by filtration, washed well with water and dried through a funnel to afford the target product 2,4-dichloro-5-methylthieno[2,3-d]pyrimidine (1.3 g, 35.5% yield). The structure of the product was confirmed by 1H NMR (400MHz, CDCl3): δ 7.62 (d, J=6.4Hz, 1H), 7.43 (d, J=6.4Hz, 1H).