Reactions of Trifluorotriacetic Acid Lactone and Hexafluorodehydroacetic Acid with Amines: Synthesis of Trifluoromethylated 4-Pyridones and Aminoenones

Abstract

Dehydroacetic acid and triacetic acid lactone are known to be versatile substrates for the synthesis of a variety of azaheterocycles. However, their fluorinated analogs were poorly described in the literature. In the present work, we have investigated reactions of trifluorotriacetic acid lactone and hexafluorodehydroacetic acid with primary amines, phenylenediamine, and phenylhydrazine. While hexafluorodehydroacetic acid reacted the same way as non-fluorinated analog giving 2,6-bis(trifluoromethyl)-4-pyridones, trifluorotriacetic acid lactone had different regioselectivity of nucleophilic attack compared to the parent structure, and corresponding 3-amino-6,6,6-trifluoro-5-oxohex-3-eneamides were formed as the products. In the case of binucleophiles, further cyclization took place, forming corresponding benzodiazepine and pyrazoles. The obtained 2,6-bis(trifluoromethyl)-4-pyridones were able to react with active methylene compounds giving fluorinated merocyanine dyes.

Keywords

• 4-hydroxy-2-pyrone
• 4-pyridone
• aminoenone
• trifluoromethylated heterocycles
• regioselective reactions