Condensação de knoevenagel na síntese de novos sistemas heteroaroil-cumarínicos trifluormetil substituídos

Abstract

With the aim to verify the influence of the presence of the trifluoromethyl group and the heterocyclic precursor in the heteroaroyl-coumarin synthesis, this dissertation describes firstly a methodology optimization to obtain some 1-cyanoacetylpyrazoles (6) described in the literature. Using cyanoacetohydrazide (4) and 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoro-3-alken-2-ones (5), [CF3C(O)CH=COR(R1), where R = Me, Et; R1 = Me, Ph, 4-BrC6H4, 2-furyl e 2-thienyl], as the reagents, it was possible to obtain three novel examples of 3-alkyl(aryl/heteroaryl)-1-cyanoacetylpirazolines (6) employing the above cited methodology in 88 92 % yields. In a subsequent step, aiming to obtain the target compounds, it was performed the synthesis of a new series of 3-(5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazol-1-carbonyl)-2-imine-2H-cromenes (8) (4 examples) by Knoevenagel reaction type. This procedure involved reactions of 3-methyl-1-cyanoacetyl-pyrazoline (6a) and four polysubstituted salicylic aldehydes (7), in presence of ethanolic solution of NaOH 15% in ethanol, in 50 78 % yields. Since the 2-imine-2H-chromenes (8) had poor solubility in many organic solvents and difficulty to characterize using the conventional methods of structural analysis, it was decided to perform a derivatization reaction of compounds 8, which employed aqueous hydrochloric acid 36% in ethanol. This imino group hydrolysis reaction conducted to the new series of trifluoromethyl substituted pyrazolyl-coumarins 9 (4 examples) in 80 91 % yields. Finally, reactions to obtain heteroaroyl-coumarins in absence of the trifluoromethyl group and from a pyrrol nucleous were performed. According to the same methodology used to obtain pyrazolyl-coumarins 8 and 9, now it was used 2-cyanoacetyl-1-methylpyrrole (12) and five salicylic aldehydes (7), as precursors, resulting directly in a new series of five pyrrolyl-coumarins 14 in 40 60 % yields. The most of synthetic pyrrolyl-iminocoumarin intermediates 13 (analogs to 8), were not XXIV isolated due to the formation of small amount of this product in some cases. In the most of cases compounds 13 are spontaneous converted into coumarins 14 at the first step of the reaction. However, aiming the total convertion of 13 into 14, it was adopted the same convertion method of 8 into 9, i.e., heating compounds 13 in aqueous hydrochloric acid 36% in ethanol. The compounds were characterized by uni- and bidimensional NMR Espectroscopy of 1H, 13C {1H} and 2D HMBC, Infra-red Espectroscopy, Gas Chromatography Coupled of Mass Espectroscopy (GC-MS), X-Ray Diffraction, High Resolution Mass Spectrometry (HRMS). The purity of all new compounds was determined by CHN Elemental Analysis.