Efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones using heterogeneous solid acid catalysts: Unexpected formation of 2,3-dihydro-2-(4-(tetrahydro-2H- pyran-2-yloxy)butyl)quinazolin-4(1H)-one

The heterogeneous solid acid catalysts Amberlyst-15 and silica-HClO ₄ displays efficient catalytic properties for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from anthranilamide and various aldehydes/ketones under mild reaction conditions and in good yields. These catalysts also showed good catalytic activity for condensation of anthranilamide with a cyclic enol ether 3,4-dihydropyran and led to formation of new unexpected quinazolinone product 6 comprising two dihydropyran moieties. The new product 6 has been reported for the first time and is fully characterized using 2D-NMR data. Furthermore, both solid acid catalysts can be easily recycled without significant loss of activity.