Synthesis of Schiff Bases and Isoindolyl- and Thiazolyl-Substituted Quinolines from 6-Amino-2-methylquinolin-4-ol

Reactions of 6-amino-2-methylquinolin-4-ol with salicylaldehyde, phthalic anhydride, phenyl isothiocyanate, and ammonium thiocyanate afforded 6-[(2-hydroxybenzylidene)amino]-2-methylquinolin-4-ol, 2-(4-hydroxy-2-methylquinolin-6-yl)-1 H -isoindole-1,3(2 H )-dione, N -(4-hydroxy-2-methylquinolin-6-yl)- N ′-phenylthiourea, and 1-(4-hydroxy-2-methylquinolin-6-yl)thiourea, respectively. Heterocyclizations of the latter with ethyl bromoacetate and bromacetophenone led to the formation of 2-[(4-hydroxy-2-methylquinolin-6-yl)­imino]-1,3-thiazolidin-4-one and 2-methyl-6-[(4-phenyl-1,3-thiazol-2(3 H )-ylidene)amino]quinolin-4-ol, respectively.