Solid-phase syntheses of 1,2,4-trisubstituted urazole and thiourazole derivatives

Solid-phase syntheses of 1,2,4-trisubstituted urazole and thiourazole derivatives have been accomplished. The synthesis began with the coupling of carbonylimidazole-Wang resin with a disubstituted hydrazine. The resultant carbazate was coupled with an isocyanate or isothiocyanate. Subsequent heating of the resin in the presence of triethylamine or potassium t-butoxide induced cyclization and released the desired (thio)urazole into solution. Most of the products were obtained in high yields and purities. Structural diversity can be further expanded at the R(2) substituent by performing the palladium-mediated Suzuki coupling reaction.