Palladium-Catalyzed 8-Exo Trig Intramolecular Heck Reaction Under Microwave Irradiation in the Presence of Basic Alumina

Abstract

The Heck cross-coupling reaction has been employed for efficient conversion of quinolines to benzoxocinoquinoline through a microwave-assisted palladium-catalyzed intramolecular cyclization in the presence of basic alumina.

GRAPHICAL ABSTRACT

Keywords:

• Basic alumina
• benzoxocinoquinoline
• Heck cross-coupling reaction
• microwave irradiation
• solid-phase synthesis

ACKNOWLEDGMENTS

We thank the Council of Scientific and Industrial Research (CSIR), New Delhi, for financial support in the form of fellowships to P. Saha, S. Mondal, A. Hazra, S. Naskar, A. Maity, K. B. Sahu, and R. Paira. We are also thankful to B. Achari, emeritus scientist, CSIR, for suggestions and encouragement. Our special thanks go to B. C. Ranu of Indian Association for the Cultivation of Science (IACS), Kolkata, for his generous cooperation in utilizing the microwave instrument.

Notes

^a All the studies were performed by using 4a, Pd(OAc)₂ catalyst under microwave irradiation at 250 W.

^b Isolated yield.

^c No reaction.

^a Reaction conditions: basic alumina (250 mg), Heck precursor (1 equiv.), Pd(OAc)₂ (6 mol%), and TBAB, under microwave irradiation (250 W), reaction time 12 min, temperature 120 °C.

^b Isolated yield. The products were characterized by MS and ¹H and ¹³C NMR spectroscopy.