a) General procedure for the preparation of ethyl 4-(2-cyano-2-ethoxycarbonylvinylamino)benzoate: triethyl orthoformate (33.3 mL, 0.2 mol) was mixed with ethyl cyanoacetate (21.3 mL, 0.2 mol) in acetic acid anhydride (80 mL), and the mixture was heated for 5 hr at 150-160 °C. Upon completion of the reaction, it was cooled to room temperature and the solvent was removed by distillation under reduced pressure to give ethyl 2-cyano-3-ethoxyacrylate as a yellow solid (28.5 g, 84% yield).
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