A series of biologically important 3-substituted-2-thixo-4quinazolinones have been synthesized starting from methyl 2isothicyanatobenzoate and amines without the use of additives under mild reaction conditions in water. This transformation tolerates a wide range of amines, which include anilines, alkyl amines, and hydrazines, to afford 60 diverse 3-substituted-2-thixo-4-quinazolinones including 34 new compounds at 60 °C for 30 min in good yields. This method avoids the use of organic solvent and the generation of toxic waste to demonstrate a cost efficient, green and sustainable method for the synthesis of 2-thixo-4-quinazolinone derivatives as valuable heterocycles for biological and materials studies.