Intramolecular Aminolysis of 2′-Aminochalcone Epoxides Using InBr₃ or BiCl₃ as Efficient Catalysts

Abstract

In the synthesis of aza-flavanone derivatives, several metal halides were screened for their catalytic activity. Among them, BiCl₃ and InBr₃ catalyze the ring opening of 2′-aminochalcone epoxides followed by intramolecular aminolysis under mild conditions. The reactions proceed efficiently at room temperature to afford highly functionalized 2-aryl-3-hydroxy-2,3-dihydro-4-quinolones (aza-flavanones) in excellent yields (82–92%). Intermolecular aminolysis of 2′-aminochalcone epoxides with aniline derivatives failed under the same catalytic conditions.

GRAPHICAL ABSTRACT

Keywords:

• 2′-Aminochalcones/epoxides
• aminolysis
• 2-aryl-3-hydroxy-2,3-dihydro-4-quinolones
• epoxide ring opening
• metal halides

ACKNOWLEDGMENTS

This work was financially supported by the Indian Institute of Technology Roorkee through Ministry of Human Resource Development (MHRD), New Delhi. B. V. B. and H. K. thank MHRD for the award of fellowships. The reviewers are highly appreciated for their valuable suggestions.

Notes

^a GaCl ₃ , SnCl₂, ZnO, CuBr₂, CeCl₃ · 7H₂O, TeCl₄, LaCl₃, LiBr, AuBr₃, and MgBr₂ · Et₂O failed to give products even for longer reaction time.

^b Yields refer to isolated products 1b in 10 mol% catalyst loading.

^a Side product 3-bromo-2-phenyl-2,3-dihydroquinolin-4(1H)-one (7%).

^a All reactions were carried out according to the general procedure.

^b Reaction time: 45–50 min at room temp. in all entries.

^c Yields refer to isolated products with InBr₃ catalyst (10 mol%).