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Step B: Synthesis of 2-(trifluoromethyl)pyrimidine-5-carbaldehyde To a solution of ethyl 2-(trifluoromethyl)pyrimidine-5-carboxylate (25.5 g, 116.0 mmol) in dichloromethane (580 mL) was slowly added diisobutylaluminum hydride (1.0 M, 130.0 mL, 130.0 mmol) at -78 °C. The reaction mixture was kept stirred at -78 °C for 2 hours. Subsequently, the reaction was quenched by slow addition of hydrochloric acid (2.0 M). The mixture was gradually warmed up to ambient temperature. The mixture was extracted with ether (3 times). The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated to give the target product 2-(trifluoromethyl)pyrimidine-5-carbaldehyde (28.2 g).