Urea/Thiourea as Ammonia Surrogate: A Catalyst-Free Synthesis of 2-Substituted 2,3-Dihydroquinazolin-4(1H)-ones/Quinazoline-4(3H)-ones

Abstract

Urea/thiourea have been identified as an effective ammonia surrogate in the construction of quinazolin-4(3H)-one ring. This strategy afforded a simple and catalyst-free synthesis of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones and quinazolin-4(3H)-ones via the reaction of isatoic anhydride and aryl aldehydes in the presence of urea or thiourea in ethanol. The reaction proceeded well to afford the quinazolin-4(3H)-one or its dihydro derivative, depending on the nature of carbonyl compounds employed.

GRAPHICAL ABSTRACT

Keywords:

• Aldehyde
• isatoic anhydride
• quinazolin-4(3H)-one
• urea

ACKNOWLEDGMENTS

Help from the analytical department for the analytical data is appreciated. We thank Dr. Vyass and Kavi Raj for their helpful discussions.

Notes

^a Reaction conditions: All the reactions were carried out using isatoic anhydride 1 (0.003 mol), 2-bromobenzaldehyde 2a (0.0033 mol), and urea (0.0033 mol) in EtOH (4 mL) at 80–85 °C under open air.

^b Isolated yield.

^c Thiourea (0.0033 mol) was used in place of urea.

^a Reaction conditions: All the reactions were carried out using isatoic anhydride 1 (0.003 mol), aldehyde 2 (0.0033 mol), and urea (0.0033 mol) in EtOH (4 mL) at 80–85 °C under open air.

^b Isolated yield.

^c Thiourea (0.0033 mol) was used in place of urea.

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