RESUMO
Functionalized 2-salicyloylfurans and 2-benzoyl-8H-thieno[2,3-b]indoles were prepared under mild conditions by reaction of 3-halochromones with ß-ketoamides and 1,3-dihydroindole-2-thiones, correspondently. The subsequent oxidative cyclization of the products resulted in formation of the corresponding furo[3,2-b]chromen-9-ones. These molecules could also be directly prepared from 3-halochromones using a one-pot protocol. The cyclization reactions reported herein are mechanistically surprising as they proceed via the oxygen and not via the (more nucleophilic) nitrogen atom of the ß-ketoamide.
Assuntos
Amidas/química , Benzopiranos/síntese química , Furanos/síntese química , Indóis/síntese química , Tionas/síntese química , Catálise , Ciclização , Estrutura Molecular , Oxirredução , Ácido Salicílico/química , EstereoisomerismoRESUMO
Reaction of 6-arylamino-1,3-dialkyluracils with anhydrides of polyfluorocarboxylic acids in the presence of pyridine and subsequent cyclization with concentrated H2SO4 gave the corresponding 1,3-dialkyl-5-(polyfluoroalkyl)pyrimido[4,5-b]quinoline-2,4(1H,3H)-diones (5-polyfluoroalkyl-5-deazaalloxazines). The reactivity of these compounds towards nucleophilic reagents, such as sodium cyanoborohydride, acetophenone, nitromethane, potassium cyanide, indole and p-thiocresol, as well as Suzuki and Sonogashira couplings are described. The nucleophilic addition takes place at the 5-position of the 5-deazaalloxazine system and is in many cases irreversible to give 5,10-dihydropyrimido[4,5-b]quinoline-2,4(1H,3H)-dione derivatives in good to excellent yields.
Assuntos
Compostos Aza/síntese química , Flavinas/síntese química , Quinolinas/síntese química , Alquilação , Compostos Aza/química , Ciclização , Flavinas/química , Halogenação , Piridinas/química , Quinolinas/química , Uracila/análogos & derivadosRESUMO
Reactions of 3-methoxalyl-, 3-polyfluoroacyl- and 3-aroylchromones with dimethyl 1,3-acetonedicarboxylate and 1,3-diphenylacetone in the presence of DBU proceed at the C-2 atom of the chromone system with pyrone ring-opening and subsequent formal [3 + 3] cyclocondensation to functionalized 2-hydroxybenzophenones, 6H-benzo[c]chromenes and benzo[c]coumarins, depending on the substituent at the 3-position. An NMR study and X-ray crystallographic analysis are reported. The compounds synthesized can be considered as promising scaffolds for the design of the novel UV-A/B and UV-B filters.
Assuntos
Benzopiranos/síntese química , Cumarínicos/síntese química , Ácidos Cetoglutáricos/química , Benzopiranos/química , Cumarínicos/química , Cristalografia por Raios X , Ciclização , Espectroscopia de Ressonância Magnética , Estrutura MolecularRESUMO
An efficient and practical route to 7-azaindole framework has been developed by one-pot, three-component cyclocondensation of N-substituted 2-amino-4-cyanopyrroles, various aldehydes, and active methylene compounds in ethanol or acetic acid at reflux. Reactions involving tetronic acid, indane-1,3-dione, dimedone, and 5-phenylcyclohexane-1,3-dione gave carbocyclic fused 7-azaindoles, whereas Meldrum's acid, benzoylacetonitrile, and malononitrile resulted in the highly substituted 7-azaindole derivatives, making this strategy very useful in diversity-oriented synthesis (DOS).
Assuntos
Técnicas de Química Combinatória/métodos , Indóis/síntese química , Bibliotecas de Moléculas Pequenas/síntese química , Aldeídos/química , Técnicas de Química Combinatória/economia , Ciclização , Indóis/química , Metano/análogos & derivados , Pirróis/química , Bibliotecas de Moléculas Pequenas/químicaRESUMO
A divergent and regioselective approach to fused pyridines was developed through formal [3 + 3] cyclocondensations from simple 2,3-unsubstituted chromones or their enaminone precursors.
Assuntos
Cromonas/química , Piridinas/síntese química , Cromonas/síntese química , Ciclização , Piridinas/química , EstereoisomerismoRESUMO
The first synthesis of 3-methoxalylchromone was described. The reaction of the latter with electron-rich aminoheterocycles afforded a set of heteroannelated pyridines bearing a CO(2)Me substituent located at the α-position of the pyridine core.
Assuntos
Cromonas/síntese química , Purinas/química , Modelos Moleculares , Estrutura MolecularRESUMO
An expedient synthesis of a series of 2-pyrones, bearing a CF 3 group at the 6-position and aryl group at position 4, from readily available aryl-4,4,4-trifluorobutane-1,3-diones, PCl 5, and sodium diethyl malonate is described.
Assuntos
Ácidos Carboxílicos/síntese química , Compostos de Flúor/síntese química , Oxigênio/química , Piranos/síntese química , Ácidos Carboxílicos/química , Compostos de Flúor/química , Metilação , Estrutura Molecular , Piranos/químicaRESUMO
Polyhaloalkyl-substituted chromones, gamma-pyrones, and beta-furanones react with salicylaldehydes in the presence of piperidine to give a wide variety of fused 2H-chromenes in good yields. This novel annulation reaction presumably proceeds by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation.
Assuntos
Benzopiranos/síntese química , Aldeídos/química , Cromonas/química , Furanos/química , Pironas/químicaRESUMO
8-Aza-5,7-dimethyl-2-trifluoromethylchromone reacts with alkyl mercaptoacetates in the presence of triethylamine to give pyrido derivatives of 2-oxa-7-thiabicyclo[3.2.1]octane, which undergo the reductive ring opening to alkyl 2-[[3-(4,6-dimethyl-2-oxo-1,2-dihydropyridin-3-yl)-3-oxo-1-(trifluoromethyl)propyl]sulfanyl]acetates. The latter can be also obtained directly from 8-aza-5,7-dimethyl-2-trifluoromethylchromone and behave as the masked alpha,beta-unsaturated ketone, 4,6-dimethyl-3-(4,4,4-trifluorobut-2-enoyl)pyridin-2(1H)-one. This compound was independently synthesized from 3-acetyl-4,6-dimethyl-2-pyridone, and its synthetic potential was studied. A wide variety of 2-pyridone derivatives containing the CF(3) group have been prepared in good to moderate yields.
Assuntos
Compostos Aza/química , Cromonas/química , Fluorocarbonos/química , Piridonas/síntese química , Compostos de Sulfidrila/química , Acetatos/química , OxirreduçãoRESUMO
Reactions of 2-polyfluoroalkylchromones with (perfluoroalkyl)trimethylsilanes proceed as a 1,4-nucleophilic perfluoroalkylation to give 2,2-bis(polyfluoroalkyl)chroman-4-ones with high regioselectivity and good yields after acid hydrolysis. Oxidation of 6-methyl-2,2-bis(trifluoromethyl)chroman-4-one with a mixture of K2S2O8 and CuSO4 in aqueous acetonitrile leads to fluorinated analogues of natural lactarochromal and the corresponding acid. Reduction of substituted 2,2-bis(trifluoromethyl)chroman-4-one with sodium borohydride in methanol and subsequent dehydration of chromanols in refluxing xylene in the presence of p-toluene sulfonic acid gives 2,2-bis(trifluoromethyl)chromenes, which are fluorinated analogues of natural precocenes.
Assuntos
Benzopiranos/síntese química , Cromonas/química , Hidrocarbonetos Fluorados/química , Compostos de Trimetilsilil/química , Benzopiranos/química , Metilação , EstereoisomerismoRESUMO
[reaction: see text] 2-Polyfluoroalkylchromones react with 1,3,3-trimethyl-3,4-dihydroisoquinolines to give zwitterionic axially chiral 6,7-dihydrobenzo[a]quinolizinium derivatives in high yields. In addition, performing this reaction with aromatic methylketimines is a simple and convenient synthesis of 2,6-diaryl-4-polyfluoroalkylpyridines.
RESUMO
[reaction: see text] 8-Aza-5,7-dimethyl-2-trifluoromethylchromone reacts with alkyl mercaptoacetates to give pyrido derivatives of 2-oxa-7-thiabicyclo[3.2.1]octane, which undergo the reductive ring-opening to sulfanyl acetates. The latter compounds are useful CF(3)-containing building blocks for the preparation of a variety of 2-pyridone derivatives.
RESUMO
Oxidation of 2-(trifluoromethyl)-1,2-dihydro-4H-thieno[2,3-c]chromen-4-ones 2 with H(2)O(2) in AcOH gives 2-(trifluoromethyl)-1,2-dihydrothieno[2,3-c]chromen-3,3,4-triones 3, which are transformed into 3-hydrazinopyridazine derivatives 4 in high yields by treatment with hydrazine hydrate in ethanol.