Síntese, propriedades fotofísicas de 6-amino-4- (trifluormetil)quinolinas e sua aplicação na construção de sistemas triazolil-quinolínicos

Abstract

The present work describes the synthesis, structural study and evaluation of the photophysical properties of novel 6-amino-4-(trifluoromethyl)quinolines, as well as their application in obtaining an unpublished series of 2-alkyl(aryl/heteroaryl)-6-(4-alkyl(aryl)-1H- 1,2,3-triazol-1-yl)-4-(trifluoromethyl)quinolines, 2-alkyl = Me; 2-aryl(heteroaryl) = Ph, 4-Me- C6H4, 4-F-C6H4, 4-NO2-C6H4, 2-furyl; 4-alkyl(aryl) = -CH2OH, -(CH2)5CH3, Ph. Structural and electronic properties were investigated by mass spectrometry (GC/MS), 1H-, 13C- and 19F-NMR and by single-crystal X-ray diffraction. The methodology begins with the synthesis of an unprecedented series of precursors namely (Z)-4-alkyl(aryl)-4-(4-aminophenyl)amino)-1,1,1-trifluoro-3-alken-2-ones (3), obtained from reactions between 4-methoxy-1,1,1-trifluoro-3-alken-2-ones (1) and pphenylenediamine (2) in yields of 71-87%. The enaminoketones 3, on the other hand, were successfully used in regioselective reactions of intramolecular cyclization in sulfuric acid, bringing the corresponding 6-amino-4-(trifluoromethyl)quinolines (4) in yields of 22-87%. In sequence, the 6-aminoquinoline derivatives 4 had their photophysical properties as absorption, emission, fluorescence quantum yield and Stokes displacement evaluated and related to theoretical calculations (TD-DFT). An initial evaluation of thermal stability using DSC/TGA techniques was also obtained in the present study. The quinolines 4 were also converted to an unpublished series of 6-azido-4-(trifluoromethyl)quinolines (5) in 78-87% yields employing diazonium salts and sodium azide. Finally, the azides originating 5 reacted with different terminal alkynes (6-8) under a copper-catalysed 1,3-dipolar cycloaddition reactions (CuAAC - Click Chemistry), to performed the exclusive synthesis of 1,4-disubstituted 1,2,3-triazolylquinoline derivatives (9-11) in yields of 77-95% (12 examples).