Quinazolin-2-ones Having a Spirohydantoin Ring. III. A General and Efficient Synthesis of 3'-Substituted Spiro[imidazolidine-4, 4'(1'H)-quinazoline]-2, 2', 5(3'H)-triones

Abstract

The reaction of 1-carbamoylisatins 2 with 2-ethyl-2-isothiourea hydrobromide in the presence of triethylamine followed by acid-catalyzed cyclization of the resulting 4-(2-ethyl-2-isothioureido)carbonyl-3, 4-dihydro-4-hydroxy-2(1H)-quinazolinones 7 provides a general and high-yielding route to 3'-substituted spiro[imidazolidine-4, 4'(1'H)-quinazoline]-2, 2'5(3'H)-triones 8.