Síntese de 3-acil-4-aril-2-(trifluormetil)-2-hidróxi-3,4,7,8-tetraidro-2h-cromen-5(6h)-onas via reações multicomponentes e derivatizações

Abstract

This work describes firstly the synthesis of a new series of 3-acyl-4-aryl-2-(trifluoromethyl)-2-hydroxy-3,4,7,8-tetrahydro-2H-chromen-5(6H)-ones (4) (thirty-four examples) through the methodology of multicomponent reactions involving 1,3-ciclohexadione (1), six aryl aldehydes (2) and six 4-alkoxy-4-alkyl(aryl/heteroaryl)1,1,1-trifluoro-3-alquen-2-ones (3) in the presence of triethylamine (30 mol%) in ethanol, with yields of 15-75%. In a subsequent step, were carried out derivatization reactions of trifluoromethyl substituted chromenones since their structures have several reactive sites possible to chemical modification, ie a hemi-acetal function at C2, endo and exocyclic carbonyl, C3 and C5, respectively, and an olefinic double bond conjugaste between C8a and C4a. The chemical derivatizations in chromenones (4) were initiated by partial oxidative aromatization involving iodine and alcohol solvent reaction by using conventional methods and heating via microwave irradiation. These procedures led to a series of 3-acyl-2-hydroxy-4-aryl-5-alkoxy-2-(trifluoromethyl)chromans (eleven examples) in 50-89%yield. Subsequently, reduction reactions of 2-hydroxy-2H-chromenones (4) and chromenes (5) using NaBH4 in ethanol as solvent allowed to obtain of 3-acyl-8a-hydroxy-4-aryl-2-(trifluoromethyl)-octaidrochromen-5-ones (8) (nine examples) and 4-phenyl-2-(trifluoromethyl)-2-hydroxy-3-(1-hydroxyethyl)-5-methoxychroman (9) in 25-63% and 83% yield, respectively. Finally, rearrangement reactions between chromenone ring (4) and hydrazine monohydrate resulted in a new series of 2-[(3(5)-trifluormethyl-5(3)-alkyl/aryl-1H-pyrazole-4-il)-aryl]-3-hydroxyciclohex-2-en-1-one (10) (six examples) to yield 63-90%. An example of the series 10 was subjected to reactions of partial oxidative aromatization and N-alkylation, where aryl = phenyl, and 4-MeOC6H4 and alkyl= Me. The partial aromatization reaction, in the presence of iodine/methanol, conducted to formation of 4-(2,6-dimethoxyphenyl-4-methoxyphenyl)phenylmethyl-5(3)-methyl-3(5)-trifluoromethyl-1H-pyrazole (11) in 72% yield. The N-alkylation reaction of 11 employing benzyl chloride, NaH in DMF at room temperature led to the regioselective (isomer 1,5) and allowed the isolation of 2-[(1-benzyl-5-trifluoromethyl-3-methyl-1H-pyrazole-4-yl)phenylmethyl]-3-hydroxyciclohexen-2-en-1-one (12) with 69% yield. The compounds were characterized by 1H and 13C {1H}, 19F, e 2D HSQC NMR Spectroscopy, Gas Chromatography coupled to Mass Spectrometry (GC-MS), Liquid Chromatography (LC-ESI). Their purity was determined by CHN Elemental Analysis and High-resolution Mass Spectrometry (HRMS).