Solvent-free synthesis of dibenzo[b,j][1,10]phenanthroline derivatives using Eaton’s reagent as catalyst

ABSTRACT

A new class of dibenzo[b,j][1,10]phenanthrolines has been prepared. The synthon acridones were achieved in very good yield by a one-pot reaction of 2-amino-5-chloro or 2′-chloro/flouro-substituted benzophenones with 1,2-cyclohexanedione in the presence of freshly prepared Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) without solvent, through Friedländer synthesis. Then these intermediates were reacted with 2-amino-3,5-dibromobenzaldehyde to afford 1,3-dibromo-10-chloro-8-aryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline. Also an one-pot reaction between 2 mol of 2-amino-5-chloro aryl benzophenones with 1 mol of 1,2-cyclohexanedione to get 3,10-dichloro-5,8-diaryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline has also been reported. The newly synthesized structures of the compounds were deduced by spectroscopic techniques.

GRAPHICAL ABSTRACT

KEYWORDS:

• Dibenzo[b,j][1,10]phenanthrolines
• Eaton’s reagent
• Friedländer synthesis
• solvent free mechanism

Acknowledgments

Rajendran Satheeshkumar is thankful to the University Grant Commission (UGC-SAP), New Delhi, for BSR—Senior Research Fellowship, which is gratefully acknowledged. Dr. Karnam Jayarampillai Rajendra Prasad greatly acknowledged the UGC-Emeritus fellowship for research.