Regioselective synthesis and biological evaluation of N-substituted 2-aminoquinazolin-4-ones.

The reaction of methyl anthranilates with N-arylcyanamides in the presence of p-TsOH in t-BuOH under reflux afforded predominantly 3-arylquinazolin-4-ones. In contrast, the reaction of the same reactants with TMSCl in t-BuOH at 60 °C followed by the Dimroth rearrangement in aqueous ethanolic sodium hydroxide gave exclusively the regioisomers, 2-(N-arylamino)quinazolin-4-ones. The regioselective synthesis of N-aryl-substituted 2-aminoquinazolin-4-ones can be further applied to the synthesis of benzimidazo[2,1-b]quinazolin-12-ones.

Practical synthesis of N-substituted cyanamides via Tiemann rearrangement of amidoximes.

A facile and general synthesis of various N-substituted cyanamides was accomplished by the Tiemann rearrangement of amidoximes with benzenesulfonyl chlorides (TsCl or o-NsCl) and DIPEA.