p-Toluenesulfonic acid → 4-Methyl-2-ethylsulfanyl-pyrimidine-5-carboxylic acid ethyl ester

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A mixture of ethyl acetoacetate (6.37 mL, 50.0 mol), dimethylformamide dimethylacetal (8.94 g, 75.0 mmol), and catalytic p-toluenesulfonic acid was heated at 100° C. for 2 h. After cooling to rt, the mixture was diluted with N,N-dimethylformamide (DMF; 50 mL) and 2-ethylisothiourea hydrobromide (9.10 g, 50.0 mmol) was added. After heating the at 100° C. for 18 h, the mixture was cooled to rt and concentrated to give a crude residue, which was purified by FCC (EtOAc/hexanes) to give 7.1 g (61%) of a solid. 1H NMR (CDCl3): 8.97-8.91 (m, 1H), 4.43-4.35 (m, 2H), 3.24-3.15 (m, 2H), 2.81-2.72 (m, 3H), 1.47-1.35 (m, 6H).

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