Ethyl orthoformate → 4-(4-Cyano-2-methoxyphenyl)-5-ethoxy-2,8-dimethyl-1,4-dihydro-1,6-naphthyridine-3-carbonitrile

Participants

Reaction Conditions

Reaction Steps

3620 mg (10.83 mmol) of 4-(4-cyano-2-methoxyphenyl)-2,8-dimethyl-5-oxo-1,4,5,6-tetrahydro-1,6-naphthyridine-3-carbonitrile are suspended in 150 ml (901 mmol) of anhydrous triethyl orthoformate. The reaction mixture is heated to 140° C. Then 10 drops of concentrated sulfuric acid are added each hour. After complete reaction has been detected (analytical HPLC; reaction time about 36 h), the reaction mixture is cooled to room temperature and the precipitated product is filtered off. The precipitate is washed with ethyl acetate and diethyl ether and then purified by flash chromatography (silica gel; mobile phase: initially dichloromethane, then isohexane/ethyl acetate 1:1). The product fractions are combined and concentrated in a rotary evaporator, and the residue is then crystallized from ethyl acetate. Drying under high vacuum results in 1160 mg (30% of theory) of the title compound in the form of yellowish crystals.

Provenance & Evidence