Palladium functionalized phosphinite polyethyleneimine grafted magnetic silica nanoparticles as an efficient catalyst for the synthesis of isoquinolino[1,2-b]quinazolin-8-ones

In this paper, a novel methodology is introduced for the synthesis of novel 5-methyl-8H-isoquinolino[1,2-b]quinazolin-8-one derivatives based on an efficient immobilized palladium catalyzed intramolecular carbon–carbon bond formation. The novel catalyst is fabricated by immobilization of Pd on phosphinite polyethyleneimine functionalized Fe3O4@SiO2 core–shell nanoparticles (denoted as Pd@OPPh2–PEI–mSiO2 NPs). In this catalyst, PEI moieties act as both a water dispersant and base in the reaction. In the key step, 3-allyl-2-(2-bromophenyl)-2,3-dihydroquinazolin-4(1H)-ones (3a–i) were synthesized via a cyclization reaction between N-allyl-2-aminobenzamides and 2-bromobenzaldehyde. The latter obtained materials then underwent an intramolecular carbon–carbon bond formation in the presence of the Pd@Ph2PO–PEI–mSiO2 catalyst to give 5-methyl-13,13a-dihydro-8H-isoquinolino[1,2-b]quinazolin-8-ones (4a–i).