A clay-mediated, regioselective synthesis of 2-(aryl/alkyl)amino-thiazolo[4,5- c]carbazoles

Abstract

The 3-aminocarbazoles 1a– e were condensed with phenyl and benzyl isothiocyanates on montmorillonite K10 clay or TLC-grade silica gel at room temperature to furnish efficiently the N-phenyl and N-benzylthioureidocarbazoles, 2a– e and 2f , respectively, within minutes. When adsorbed on montmorillonite K10 clay impregnated with para-toluene sulfonic acid (1:1, w/w) and heated at 60–70 °C, 2a– e and 2f furnished the 2-anilino and 2-benzylaminothiazolo[4,5- c]carbazoles, 3a– e and 3f , respectively, regioselectively in high yields. The cyclisation was also effective for the N-methylthioureidocarbazoles 2g– i .