Convenient one-pot synthesis of fluorinated DHPs derivatives and their further transformations

One-pot four-component reactions of aromatic aldehyde, Meldrum’s acid, ethyl-4,4,4-trifluoro-1,3-dioxobutanoate, and ammonium acetate afford ethyl 2-hydroxy-6-oxo-4-aryl-2-(trifluoromethyl)piperidine-3-carboxylate in good yields. The one-pot four-component process consists of an initial Michael addition, and a subsequent intramolecular cyclization. The effect of solvents on the reaction efficiency and yield is briefly investigated. The structure of product is further confirmed by XRD analysis. Meanwhile, the further transformation of hemi-aminal moiety to the corresponding dehydrated product is also achieved under the mild reaction conditions. The possible mechanism for the formation of product is presented.     

Preparation and properties of piperidine salts of 6-hydroxy-4,6-diaryl-5-ethoxycarbonyl-3-cyanopiperidine-2-thiones

Alkylation of piperidine salts of 6-hydroxy-4,6-diaryl-5-ethoxycarbonyl-3-cyanopiperidine-2(1H)-thiones yielded 6-hydroxy-2-alkylthio-4,6-diaryl-5-ethoxycarbonyl-3-cyano-3,4,5,6-tetrahydropyridines which were dehydrogenated with the formation of 2-methylthio-1,4- and 4,5-dihydropyridines. The oxidation of the compounds prepared has been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–80, January, 1987.     

Stereochemical aspects of formation of substituted hydrogenated 3-(1-pyridinio)-6-pyridinethiolates and synthesis of 4,6-diaryl-3-cyano-2(1H)-pyridinethiones on their basis

Regioselective and stereoselective methods were developed for the synthesis of 2-hydroxy-2,4-diaryl-3-(1-pyridinio)-5-cyano-3,4-trans-1,2,3,4-tetrahydropyridine-6-thiolates on the basis of the reactions of cyanothioacetamide with E-1-styrylpyridinium salts or aromatic aldehydes and 1-phenacyl-pyridinium bromide. The products exist in the half-chair conformation with the trans-diaxial arrangement of hydrogen atoms 3 and 4. The Michael adducts in the form of the anti conformers with the synclinal arrangement of the reaction centers act as intermediates. The obtained thiolates were converted with high yields into 4,6-diaryl-3-cyano-2(1H)-pyridinethiones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 370–375, March, 1990.     

One-pot three-component reaction of 3-(polyfluoroacyl)chromones with active methylene compounds and ammonium acetate: regioselective synthesis of novel R-containing nicotinic acid derivatives

Reactions of 3-(polyfluoroacyl)chromones with acetoacetamide and ethyl acetoacetate in the presence of ammonium acetate proceed at the C-2 atom of the chromone system with pyrone ring-opening and subsequent cyclization to 5-salicyloyl-2-methyl-6-(trifluoromethyl)nicotinamides, ethyl 5-salicyloyl-2-methyl-6-(trifluoromethyl)nicotinates, and ethyl 5-hydroxy-2-methyl-5-(polyfluoroalkyl)-5H-chromeno[4,3-b]pyridine-3-carboxylates. Similar reaction with β-aminocrotononitrile gave 5-hydroxy-2-methyl-5-(polyfluoroalkyl)-5H-chromeno[4,3-b]pyridine-3-carbonitriles.     

Synthesis of nonracemic polysubstituted cyclohexanes through cascade reactions of (2R,3S)-2-Acetyl-3-aryl-4-nitrobutanoates, adducts of Ni(II)-catalyzed michael addition

Stereoselective synthesis of ethyl-4,6-diaryl-2-hydroxy-2-methyl-5-nitro-3-formylcyclohexanecarboxylates was described. The formation of the asymmetric site of the required configuration is achieved by an enantioselective Michael addition of ethyl acetoacetate to nitroalkenes in the presence of a chiral Ni(II) complex with (R,R)-N,N′-dibenzylcyclohexane-1,2-diamine. Further reaction of the products obtained with cinnamic aldehyde led to the formation of polysubstituted cyclohexanes.     

Ring transformations of 4H-pyrans. Pyridines from 2-amino-4H-pyrans

Ring transformations of 4H-pyrans into pyridines are reported. Treatment of 2-amino-4,6-diaryl-3,5-dicyano-4H-pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5-dicyano-4,6-diaryl-2-pyridones (VI) which can also be obtained from α-benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2-amino-4,6-diaryl-5-carbethoxy-3-cyano-4H-pyrans (II) lead to 4,6-diaryl-5-carbethoxy-3-cyano-2-pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4-dihydro-2-pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2-amino-4,6-diaryl-5-carbethoxy-3-cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6-triaryl-3,5-dicyano-1,4-dihydropyridines (XV).     

Synthesis of 4,6-diaryl-1-benzyl-6-hydroxy-5,5-dimethyl-2-oxopiperidine-3-carbonitriles and their analogs via a modified Reformatsky reaction

Organozinc compounds obtained from 1-aryl-2-bromo-2-methylpropanone and zinc react with N-benzyl-3-aryl-2-cyanoacrylamides or N-[6-(2-cyano-1-oxo-3-phenylprop-2-enylamino)hexyl]-2-cyano-3-phenylacrylamide to give 4,6-diaryl-1-benzyl-6-hydroxy-5,5-dimethyl-2-oxopiperidine-3-carbonitriles or 1,6-bis(6-aryl-3-cyano-6-hydroxy-5,5-dimethyl-2-oxo-4-phenylpiperidyl)hexanes as a single isomer with trans-located piperidine hydrogen atoms.     

Reaction of oligomethylene di(3-oxobutanoate) with 1,1-disubstituted alkenes and molecular oxygen in the presence of manganese(II and/or IE) acetate

The reactions of 1,1-disubstituted ethenes with oligomethylene di(3-oxobutanoate) in the presence of manganese(II and/or III) acetate and atmospheric oxygen yielded an ω-(3-oxobutanoyloxy)alkyl 6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylate, oligomethylene di(6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylate)s, ω-hydroxyalkyl 6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylates, an ω-(3-oxobutanoyloxy)alkyl 5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylate, oligomethylene di(5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylate)s, ω-hydroxyalkyl 5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylates, and an ohgomethylene diester bearing a substituted 1,2-dioxane ring and a substituted 4,5-dihydrofuran ring. The reaction of the 1,2-dioxan-3-ols with acid gave the corresponding compounds bearing furan rings. The reaction of 1,1,6,6-tetraaryl-1,5-hexadienes with oligomethylene di(3-oxobutanoate) in the presence of manganese(III) acetate yielded macrocyclic diesters bearing two 4,5-dihydrofuran rings.     

Fluorocontaining 1,3-Dicarbonyl Compounds in the Synthesis of Pyrimidine Derivatives

Hexafluoroacetylacetone reacts with urea (thiourea) to yield respectively 4,6-bis(hydroxy)-4,6-bis(trifluoromethyl)hexahydropyrimidin-2-one(thione). The dehydration of the products and also reaction of nonsymmetrical fluoroalkyl-containing 1,3-diketones with urea (thiourea) afford substituted pyrimidines. The condensation of fluorinated 3-oxoesters and 1,3-diketones with benzaldehyde and urea (thiourea) results in 5-alkoxycarbonyl(acyl)-4-hydroxy-2-oxo(thioxo)-6-phenyl-4-fluoroalkylhexahydropyrimidines that on dehydration furnish 5-alkoxycarbonyl(acyl)-2-oxo(thioxo)-4-phenyl-6-fluoroalkyltetrahydropyrimidines. Ethyl 7-nonafluorobutyl-5-phenyl-2,3-dihydrothiazolo[3,2-a]pyrimidine-6-carboxylate hydrobromide forms in reaction of dibromoethane with ethyl ether of 2-thioxo-4-phenyl-6-nonafluorobutyltetrahydropyrimidine.     

Heterodiene synthesis

2-Phenyl-4,6-diaryl-1,2-dihydro-sym-triazines react with hexafluoro-2-butyne as a dienophile to give 4,5-bis(trifluoromethyl)-2,6-diarylpyrimidines.See [1] for communication V.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 122–123, January, 1977.     

Trifluoroacetylation of ethyl 2,4-dioxopentanoate. The first synthesis of 4-oxo-6-(trifluoromethyl)-4<Emphasis Type="Italic">H</Emphasis>-pyran-2-carboxylic acid and its derivatives

Condensation of ethyl 2,4-dioxopentanoate with ethyl trifluoroacetate in the presence of NaOEt leads to ethyl 4-oxo-6-(trifluoromethyl)-4H-pyran-2-carboxylate, from which the corresponding acid and its amide, as well as 4-hydroxy-6-(trifluoromethyl)pyridine-2-carboxamide were obtained. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 537–538, March, 2007.     

Manganese(III)-mediated intermolecular cyclization reactions of alkenes and active methylene compounds

The reactions of 1,1-diphenylethene, 1,1-bis(4-chlorophenyl)ethene, 1,1-bis(4-methylphenyl)ethene, and 1,1-bis(4-methoxyphenyl)ethene with 3,5-diacetyl-2,6-heptanedione in the presence of manganese(III) acetate in acetic acid at 80° yielded 4,6-diacetyl-8,8-diaryl-1,3-dimethyl-2,9-dioxabicyclo[4.3.0]non-3-enes (41-48%), 5-acetyl-2,2-diaryl-6-methyl-2,3-dihydrobenzo[b]furans (20–21%), 3-acetyl-5,5-diaryl-2-methyl-4,5-dihydrofurans (5–10%), and benzophenones (3–7%). Similarly, the reactions of 1,1-diarylethenes with dimethyl 2,4-diacetyl-1,5-pentanedioate or diethyl 2,4-diacetyl-1,5-pentanedioate gave the corresponding 4,6-bis(alkoxycarbonyl)-8,8-diaryl-1,3-dimethyl-2,9-dioxabicyclo[4.3.0]non-3-enes in moderate yields.     

A tandem multi-component synthesis of 5,7-diaryl-5,6,7,8-tetrahydro-1H-pyrido[3,4-b][1,4]thiazin-2(3H)-ones

The five-component reaction of ethyl 2-[(2-oxopropyl)sulfanyl]acetate, aromatic aldehydes, and ammonium acetate affords two diastereomers of 5,7-diaryl-5,6,7,8-tetrahydro-1H-pyrido[3,4-b][1,4]thiazin-2(3H)-ones via a novel tandem Mannich-enamine-substitution sequence. Presumably, they are generated from ethyl 2-[(4-oxo-2,6-diaryl-3-piperidinyl)sulfanyl]acetates. During the formation of the trans-5,7-diaryl-5,6,7,8-tetrahydro-1H-pyrido[3,4-b][1,4]-thiazin-2(3H)-ones from ethyl 2-[(4-oxo-2,6-diaryl-3-piperidinyl)sulfanyl]acetates, the configuration at the carbon bearing an aryl group adjacent to the enamide CC double bond is inverted via ring opening and closure. When o-substituted benzaldehydes were employed in this reaction, 5,7-diaryl-5,6-dihydro-1H-pyrido[3,4-b][1,4]thiazin-2(3H)-ones were obtained via air oxidation, along with trans-5,7-diaryl-5,6,7,8-tetrahydro-1H-pyrido[3,4-b][1,4]-thiazin-2(3H)-ones.     

Design, synthesis, and biological evaluation of a library of 1-(2-thiazolyl)-5-(trifluoromethyl)pyrazole-4-carboxamides

A library of 422 1-(2-thiazolyl)-5-(trifluoromethyl)pyrazole-4-carboxamides was prepared in five steps using solution-phase chemistry. The first step in the synthesis was the reaction of ethyl 2-ethoxymethylene-3-oxo-4,4,4-trifluorobutanoate with thiosemicarbazide, which is reported in the literature to afford a 1:1 mixture of ethyl 1-thiocarbamoyl-5-(trifluoromethyl)pyrazole-4-carboxylate and ethyl 1-thiocarbamoyl-3-(trifluoromethyl)pyrazole-4-carboxylate. We reassigned the structure of the product to be a single compound, ethyl 5-hydroxy-1-thiocarbamoyl-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazole-4-carboxylate. This common intermediate was diversified by reaction with 17 alpha-bromoketones affording, in two steps, 17 1-(2-thiazolyl)-5-(trifluoromethyl)pyrazole-4-carboxylic acids. Scavenger resins were used to facilitate formation and purification of up to 27 amides from each of these acids in the last step. In addition, the Curtius reaction was applied to 12 of the acids followed by quenching with alcohols to afford a 108-member carbamate library. Certain compounds in the two libraries were toxic to C. elegans.     

Design and synthesis of new series of 3-cyanopyridine and pyrazolopyridine derivatives

Reaction of 3-cyano-4,6-dimethyl-2-pyridone with ethyl chloroacetate afforded ethyl 2-([3-cyano-4,6-dimethylpyridin-2-yl]oxy)acetate 2 and ethyl 2-(3-cyano-4,6-dimethyl-2-oxopyridin-1[2H]-yl)acetate 3 , the reaction product yield depend on the reaction condition (potassium carbonate concentration and reaction time). These compounds used as precursors to synthesize pyridine derivatives 4 , 6-10 , 15, 17-20 , furopyridines 5, 16 , pyrazolopyridine 12 , pyridopyrazolopyrimidines 14a,b . The structure of the newly synthesized compounds was confirmed by spectral data (IR, NMR, and mass spectra) and elemental analysis.     

Five-membered 2,3-dioxo heterocycles: XCIII. Spiro heterocyclization of 4,5-diaroyl-1H-pyrrole-2,3-diones with acyclic enamine. Crystalline and molecular structure of substituted 1,7-diazaspiro[4.4]nonane

4,5-Diaroyl-1-aryl-1H-pyrrole-2,3-diones reacted with ethyl 3-amino-3-phenylprop-2-enoate to give ethyl 4-aroyl-1,6-diaryl-3-hydroxy-2-oxo-8-phenyl-1,7-diazaspiro[4.4]nona-3,6,8-triene-9-carboxylates. The crystalline and molecular structures of ethyl 4-benzoyl-3-hydroxy-1-(4-methylphenyl)-2-oxo-6,8-diphenyl-1,7-diazaspiro[4.4]nona-3,6,8-triene-9-carboxylate were determined by X-ray analysis.     

The synthesis and chemistry of 2-hydroxy-4,6-bis(trifluoromethyl)pyridine-5-carboxylates

The facile two step, one pot synthesis of heretofore unknown 2-hydroxy-4,6-bis(trifluoromethyl)-pyridine-5-carboxylates by condensation of 3-amino-4,4,4-trifluoro-2-butenoate with 4,4,4-trifluoroacetoacetyl chloride and subsequent intramolecular cyclization of the resultant enamineamide is described. Methodology for the introduction of electrophiles at the 3-position and elaboration of substituents at the 2- and 5-positions is also discussed.     

Photochemical reactions of 1-methyl-4,6-diaryl-2(1H)-pyrimidinones in the presence of thiols

Photochemical reactions of 1-methyl-4,6-diaryl-2(1H)pyrimidinones 1a-b in the presence of thiols 2 are described. Irradiation of 1-methyl-4,6-diaryl-2(1H)-pyrimidinones 1a-b in benzene in the presence of thiols 2 gave the unexpected 2:1-adducts, 3-methyl-4,6-diaryl-5-aralkylthio-6-(1′-methyl-4′,6′-diaryldihydro-pyrimidin-2-on)yl-1,3-diazabicyclo[2.2.0]hexan-2-ones 3-6, of 1 and 2, whereas irradiation of 1a-b alone in benzene resulted in recovery of the unchanged 1a-b.     

Modification of 2-trifluoromethyl-1H-benzimidazole with hydroxyalkyl substituents

Alkylation of 2-(trifluoromethyl)-1H-benzimidazole with 4-bromobutyl acetate gave 4-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]butyl acetate which was deacylated by the action of hydrogen chloride in anhydrous ethanol. 4-[2-(Trifluoromethyl)-1H-benzimidazol-1-yl]butan-1-ol thus formed showed a moderate tuberculostatic activity. Alkylation of the title compound with chloromethyloxirane afforded a mixture of 1-chloro-3-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]-propan-2-ol and 1-(oxiran-2-ylmethyl)-2-trifluoromethyl-1H-benzimidazole. A new procedure was proposed for the synthesis of 2-[(2-trifluoromethyl-1Hbenzimidazol-1-yl)methoxy]ethyl acetate.     

Synthesis of 5-nitro-3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones catalyzed by metal salts. Retro-Henry reaction with formation of <Emphasis Type="Italic">N,N′</Emphasis>-disubstituted ureas

Three-component condensation of α-nitroacetophenone with aromatic aldehydes and urea in the presence of iron(III), cobalt(II), nickel(II), and copper(II) salts as catalyst led to the formation of 4,6-diaryl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones and N-benzoyl-N′-(1-aryl-2-nitroethyl)ureas. The latter were formed as a result of retro-nitroaldol (retro-Henry) reaction of intermediate 4,6-diaryl-6-hydroxy-5-nitro-3,4,5,6-tetra-hydropyrimidin-2(1H)-ones.