One-pot five-component reaction for synthesis of some novel bis-dihydroquinazolinone derivatives

An efficient and expedient procedure for the synthesis of some novel 3-(2-(4-oxo-2-aryl-1,2-dihydroquinazolin-3(4 H )-yl)ethyl)-2-aryl-2,3-dihydroquinazolin-4(1 H )-one and 3-(4-(4-oxo-2-aryl-1,2-dihydroquinazolin-3(4 H )-yl)phenyl)-2-aryl-2,3-dihydroquinazolin-4(1 H )-one derivatives is described. The method involves the one-pot five-component condensation of two molecules of isatoic anhydride, two molecules aldehyde with and one molecule of diamine in the presence of a catalytic amount of KAl(SO 4 ) 2 .12H 2 O (alum). It affords the corresponding product in high yield with very short reaction time (50-75 min).

For wide variety of aromatic aldehydes (electron withdrawing or electron donating), the desired products were obtained in very short reaction time (within 50-75 min), good to excellent yields and simple workup procedure.The solid products obtained were just filtered of the reaction mixture.Water (25 mL) was added to the resulting solid (for removal of alum), filtered and washed with hot ethanol to give purified product.All products were characterized by their IR, MS, 1 H NMR, and 13 C NMR spectral data.a Isolated yields for purified compounds.
In conclusion, the present method indicates an operationally simple and efficient one-pot fivecomponent reaction for the preparation of bis quinazolin-4(3H)-one using the inexpensive, nontoxic, and easily available KAl(SO 4 ) 2 .12H 2 O (alum) catalyst.In addition, low cost, excellent yields of products, easy experimental work-up procedure, and short reaction time make this methodology a valid contribution to the existing processes for the synthesis of bisquinazolin-4(3H)-one.

Experimental Section
General.Melting points were obtained in open capillary tubes and were measured on an electrothermal 9200 apparatus and are uncorrected.Mass spectra were recorded on a Shimadzu QP 1100 BX mass spectrometer.IR spectra were recorded on KBr pellets on a Shimadzu IR-470 spectrophotometer. 1 H and 13 C NMR spectra were determined on a Bruker 300 DRX Avance instrument at 300 and 75MHz.Elemental analysis for C, H and N were performed using a Heraus CHN rapid analyzer.All the reactions are monitored by thin layer chromatography (TLC) with UV light as detecting agent.

General Procedure for the synthesis of bis(1,2-dihydro quinazolinon-4(1H)-one) derivatives (4 a-r).
A mixture of isatoic anhydride 1 (2 mmol ), aldehyde 2 (2 mmol ), diamine 3 (1 mmol), 0.15 g (0.3 mmol) alum , and 10 mL EtOH 96% in a 50 mL flask was stirred at reflux for the time period as indicated in table 1.After completion of the reaction (monitored by TLC, ethyl acetate /n-hexane, 4:1), the solid products obtained were just filtered off the reaction mixture.Water (25 mL) was added to the resulting solid (for separation of alum), and the resulting solid was separated by filtration.The crude product was washed with hot ethanol to afford the purified product.

Table 1 .
Synthesis of bisquinazolinone 4a-r using alum as catalysts