Propylphosphonic anhydride → 1-Methyl-4-(2-phenyl-imidazo[1,2-a]pyrimidin-7-ylcarbamoyl)-1H-pyrazole-3-carboxylic acid ethyl ester

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At 0° C., propylphosphonic acid anhydride (1-propanephosphonic acid cyclic anhydride, 50% in ethyl acetate, 7.4 ml, 2.5 eq.) was added slowly to a solution of 2-phenylimidazo[1,2-a]pyrimidin-7-amine (example 1, step 1, 1.27 g, 6 mmol), 1-methyl-1H-pyrazole-3,4-dicarboxylic acid 3-ethyl ester (1.00 g, 5 mmol), and ethyldiisopropylethylamine (2.0 ml, 15 mmol) in ethyl acetate (20 ml). The mixture was stirred for 30 min at 0° C., and subsequently at RT for 48 h. The mixture was taken up in ethyl acetate, and washed with water. The combined water layers were adjusted to pH=9 (NaOH), and extracted with dichloromethane. All organic layers were combined, dried (Na2SO4), and evaporated. The title compound (580 mg, 29%) was obtained from the residue by column chromatography (silica gel, heptane:ethyl acetate=100:0-80:20). (1-Methyl-1H-pyrazole-3,4-dicarboxylic acid 3-ethyl ester was obtained by the method of Pérez et al., Spanish patent appl. ES 493459.)

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