18740-39-1

General procedure for the synthesis of 2,4-dichlorothieno[2,3-d]pyrimidines from 2,4-dihydroxythieno[2,3-d]pyrimidines: thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (12) (2.5 g, 0.012 mol) and a drop of N,N-dimethylformamide (DMF) were added to 20 mL phosphorus oxychloride (POCl3) . The reaction mixture was heated to 115°C and kept for 8 hours. After the reaction was completed, it was cooled to room temperature and the reaction mixture was slowly poured into 500 g of ice-water mixture. The solid product was collected by filtration and dissolved in dichloromethane (CH2Cl2). The insoluble material was removed by filtration and the filtrate was distilled under reduced pressure to give 1.7 g of 2,4-dichlorothieno[2,3-d]pyrimidine (13) in 56.0% yield. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6) δ 8.16 (d, J = 3.4 Hz, 1H, Ar-H), 7.62 (d, J = 3.4 Hz, 1H, Ar-H) and ESI-MS (m/z): 205.1 [M+H]+.

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