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.     

Synthesis of 3-amino-3,4-dihydroquinazolin-4-one derivatives from anthranilic acid hydrazide and dicarboxylic acids

Treatment of anthranilic acid hydrazide with 2 equiv of ethoxalyl chloride gave the corresponding diester which underwent cyclization in acetic anhydride to produce ethyl 3-(ethoxalylamino)-4-oxo-3,4-dihydroquinazoline-2-carboxylate. Acylation of anthranilic acid hydrazide first with succinic anhydride and then with ethoxalyl chloride led to the formation of 4-[2-(2-{[ethoxy(oxo)acetyl]amino}benzoyl)hydrazino]-4-oxobutanoic acid whose cyclization in acetic acid afforded N-(2-ethoxycarbonyl-4-oxo-3,4-dihydroquinazolin-3-yl)succinamic acid, while in acetic anhydride ethyl 3-(2,5-dioxopyrrolidin-1-yl)-4-oxo-3,4-dihydroquinazoline-2-carboxylate was obtained. The latter was brought into reactions with amines and hydrazine hydrate and alkaline hydrolysis. Acylation of 2-[2-(2-aminobenzoyl)hydrazinocarbonyl]benzoic acid with ethoxalyl chloride gave ethyl N-[2-(phthalimidocarbamoyl)phenyl]oxamate, and with succinic anhydride, 3-[4-oxo-3-phthalimido-3,4-dihydroquinazolin-2-yl]propionic acid. 4-[2-(2-Aminobenzoyl)hydrazino]-4-oxobutanoic acid reacted with phthalic anhydride in boiling acetic acid to give phthalazino[1,2-b]quinazoline-5,8-dione via elimination of succinic acid residue.     

Synthesis and hydrazinolysis of β-(1,3,4-oxadiazol-2-yl)pyridines

Cyclization of the hydrazide of 5-ethoxycarbonyl-2,6-dimethylpyridine-3-carboxylic acid by acylation with aromatic or aliphatic acid chlorides with subsequent boiling in POCl₃ or heating in orthoformic acid gave the corresponding ethyl 2,6-dimethyl-5-(5-R-1,3,4-oxadiazol-2-yl)pyridine-3-carboxylate. The cyclization of the reaction products with hydrazine hydrate has been studied. Cyclization of the dihydrazide of 2,6-dimethyl-3,5-pyridinedicarboxylic acid under analogous conditions gave only 3,5-bis-(5-R-1,3,4-oxadiazol-2-yl)-2,6-dimethylpyridines, containing R = 2-FC₆H₄, H.     

Synthesis of alkyl 4-(diethoxymethyl)-3-pyridin-3-ylisoxazole-5-carboxylates: useful scaffold for highly functionalised 3-(pyridin-3-yl)isoxazoles

The methyl 4-(diethoxymethyl)-3-(pyridin-3-yl)isoxazole-5-carboxylate obtained by domino 1,3-dipolar cycloaddition and elimination starting of pyridine-3-nitrile oxide and methyl 4,4-diethoxy-3-p-tolylsulfinylbut-2-enoate is a convenient scaffold for the synthesis of other new highly functionalised 3-pyridin-3-ylisoxazoles-5-carboxylic acid derivatives and isoxazole-annulated heterocycles.     

Synthesis of ethyl 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylate via regioselective dipolar cycloaddition

Efforts to prepare ethyl 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylate (1) by developing a regioselective 1,3-dipolar cycloaddition between phenyl nitrile oxide and various 4,4,4-trifluoromethyl crotonates are described. The substitution at the C2-position of crotonate dipolarophile 4 significantly influenced the regiochemistry and yield of the cycloaddition. Enol and enol ether-based crotonates underwent regioselective cycloadditions with phenyl nitrile oxide to provide 4-trifluoromethyl isoxazoles in good yields.     

Synthesis of 3-arylsulfonylmethyl-1,2,4-oxadiazole-5-carboxylic acid derivatives

Several new 3-arylsulfonylmethyl-1,2,4-oxadiazole-5-carboxylic acid derivatives have been synthesized. A typical example, 3-[(4-chlorophenylsulfonyl)methyl]-1,2,4-oxadiazole-5-carboxylic acid ethyl ester ( 2c ), was prepared from the reaction of 2-(4-chlorophenylsulfonyl)acetamide oxime ( 1c ) with ethyl oxalyl chloride. The hydrazide derivative ( 3f ) showed antihypertensive activity in rats. Various structural modifications to improve activity are discussed.     

Synthesis and Structure of 4-Indolyl-5-(thieno[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrol-6-yl)imidazoles

A procedure was proposed for regioselective acylation of methyl 2-methyl-4H-thieno[3,2-b]-pyrrole-5-carboxylate with 2-(3-indolyl)-2-oxoacetyl chloride. Reactions of the resulting methyl 6-[2-(3-indolyl)-1,2-dioxoethyl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate with aromatic aldehydes and ammonium acetate in acetic acid afforded the corresponding methyl 6-[2-aryl-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylates. The structure of methyl 6-[2-(4-chlorophenyl)-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied by X-ray analysis.     

Syntheses of substituted 1-methyl-2-(1,3,4-thiadiazol-2-yl)-4-nitropyrroles and 1-methyl-2-(1,3,4-oxadiazol-2-yl)-4-nitropyrroles

Starting from readily available ethyl-4-nitropyrrole-2-carboxylate ( 1 ), substituted 1-methyl-2-(1,3,4-thiadiazol-2-yl)-4-nitropyrroles and 1-methyl-2-(1,3,4-oxadiazol-2-yl)-4-nitropyrroles were prepared. The reaction of 1 with diazomethane gave ethyl 1-methyl-4-nitropyrrole-2-carboxylate ( 2 ). Reaction of compound 2 with hydrazine hydrate afforded the corresponding hydrazide 3 . The reaction of 3 with formic acid yielded 1-(1-methyl-4-nitropyrrole-2-carboxyl)-2-(formyl)hydrazine ( 7 ). Refluxing of the latter with phosphorus pentasulfide in xylene yielded compound 6 in 40% yield. Reaction of compound 7 with phosphorus pentoxide afforded compound 9 . Reaction of compound 3 with 1,1′-carboxyldiimidazole in the presence of triethylamine yielded 2-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-oxadiazoline-4(H)-5-one ( 11 ). Refluxing compound 3 with cyanogen bromide in methanol gave compound 12 . Compound 13 could be obtained through the reaction of compound 3 with carbon disulfide in basic medium. Alkylation of compound 13 afforded the correspanding alkylthio derivative 14 . Reaction of 1-methyl-4-nitropyrrole-2-carboxylic acid ( 15 ) with thiosemicarbazide and phosphorus oxychloride gave 2-amino-5-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazole ( 16 ). Sandmeyer reaction of compound 16 yielded 2-chloro-5-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazole ( 17 ). Refluxing of the latter with thiourea afforded 2-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazoline-4(H)-5-thione ( 18 ). Alkylation of compound 18 gave the corresponding alkylthio derivative 19 . Oxidation of the latter with hydrogen peroxide in acetic acid yielded 2-(1-methyl-4-nitro-2-pyrrolyl)-5-methylsulfonyl-1,3,4-thiadiazole ( 20 ).     

Electronic spectra of α,β-unsaturated ketones — Indole derivatives

The electronic spectra of (3-indolyl)-, (1-methyl-3-indolyl)-, and (6-nitro-3-indolyl)-substituted ,-unsaturated ketones were measured and interpreted. 3-Indolyl and N-methyl-3-indolyl substituents have a considerable bathochromic effect as compared with the phenyl group in the investigated systems as a consequence of the electron-donor effect, which surpasses that for 4-anisyl, 2,4-dimethoxyphenyl, 2-furyl, 2-thienyl, and 2-selenienyl and differs only slightly from 2-pyrrolyl. The introduction of electron-donor substituents into the p position of the benzene ring of 1-(3-indolyl)-3-phenyl-1-propenone causes a red shift of the long-wave absorption band, the difference in frequencies of which correlates with the Hammett substituent constants. Except for compounds containing a nitro group,1-(3-indolyl)-3-aryl-3-propenones and their N-methyl derivatives fluoresce well in alcohol with _max >475 nm.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 949–953, July, 1972.     

Indole derivatives C. Synthesis of ω-(3-indolyl)alkyl bromides

-(3-Indolyl)alkyl bromides, the structure of which was confirmed by alternative synthesis from-(3-indolyl)alkanols, were obtained by a modified Borodin-Hunsdiecker reaction from mercury salts of-(3-indolyl)alkanoie acids.See [1] for communication XCIX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1493–1495, November, 1974.     

5-甲基-3-喹喔啉-2-基-4-乙氧羰基异噁唑及其衍生物的合成

以α-氯代喹喔啉-2-甲醛肟(3)与乙酰乙酸乙酯的钠盐经1,3-偶极环加成制得关键中间体5-甲基-3-喹喔啉-2-基-4-乙氧羰基异噁唑(4). 以化合物4为原料在不同条件下, 合成了一系列新的1,3,4-噁二唑啉(7), 1,2,4-均三唑的Mannich碱衍生物10a～10f, 11a～11f, 12a～12f. 化合物的结构经元素分析, IR, 1H NMR和MS确认, 并对其波谱性质进行了讨论.     

Synthesis of fluoromethyl,difluoromethyl and trifluoromethyl analogues of pyrazosulfuron-ethyl as herbicides

Ethyl 1-fluoromethyl-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)pyrazole-4-carboxylate 1b , a new fluoromethyl analogue of the herbicide pyrazosulfuron-ethyl la, was prepared from ethyl 1-fluoromethylpyrazole-4-carboxylate 4b . The difluoromethyl and trifluoromethyl analogues 1c,d were also synthesized from ethyl pyrazole-4-carboxylate 2 via difluorocarbene reaction.     

Synthesis and reaction of 5-amino-3-trifluoromethylisoxazole and -pyrazole-4-carboxylic acids

5-Amino-3-trifluoromethylisoxazole- and -pyrazole-4-carboxylic acids were prepared by the reactions ot trifluoroacetonitrile oxide or -imines with cyanoacetic acid derivatives, respectively. The behavior of thus obtained aminoazole-4-carboxylic acids toward some electrophiles was examined. In acylation with acyl chlorides, the aminoisoxazole-4-carboxylate 2a was diacylated to give the (diacylamino)isoxazole-4-carboxylate 7 , whereas the analogous aminopyrazole 5a produced the cyclized pyrazolooxazinone 13 . Moreover, carbamoylation of 2a with isocyanates gave the trifluoromethylisoxazolouracils 10 .     

Steric redirection of alkylation in 1H-pyrazole-3-carboxylate esters

The alkylation of ethyl 1H-pyrazole-3-carboxylate with a variety of alkylating agents in the presence of K₂CO₃ was found to largely favor the formation of ethyl 1-substituted pyrazole-3-carboxylates. The alkylation could be sterically redirected by the use of a triphenylsilyl group (ethyl 3-(triphenylsilyl)-1H-pyrazole-5-carboxylate) to provide synthetically useful yields of ethyl 1-substituted-3-(triphenylsilyl)-1H-pyrazole-5-carboxylates. The triphenylsilyl group could be removed with Bu₄NF. Other triorganosilyl groups (TMS, TES, TBDMS) failed to provide significant redirection, while TIPS proved refractory to protodesilylation.     

Synthesis,Crystal Structure and Bioactivity of Phenazine-1-carboxylic Acylhydrazone Derivatives

A phenazine-1-carboxylic acid intermediate was synthesized from the reaction of aniline and 2-bromo-3-nitro-benzoic acid. It was then esterified and reacted with hydrazine hydrate to afford phenazine-1-carboxylic hydrazine. Finally, 10 new hydrazone compounds 3a–3j were obtained by the condensation reaction of phenazine-1-carboxylic acid hydrazide and the respective aldehyde-containing compound. The structures were characterized by ¹H and ¹³C NMR spectroscopy, MS and single crystal X-ray diffraction. The antitumor activity of the target compounds in vitro (HeLa and A549) was determined by thiazolyl blue tetrazolium bromide. The results showed that compound (E)-N′-(2-hydroxy-4-(2-(piperidine-1-yl) ethoxy) benzyl) phenazine-1-carbonyl hydrazide 3d exhibited good cytotoxic activity.     

Syntheses of substituted-oxazolo-1,3,4-thiadiazoles, 1,3,4-oxadiazoles,and 1,2,4-triazoles

Starting from readily available methyl 5-methyloxazole-4-carboxylate ( 1 ) and 4-methyl-5-oxazolylcar-boxylic acid hydrazide ( 11 ) the title compounds were prepared. The reaction of compound 1 with hydrazine hydrate afforded the corresponding hydrazide 2 . The reaction of compound 2 with formic acid yielded 1-formyl-2-(5-methyloxazole-4-carboxyl)hydrazine ( 3 ). Refluxing of the latter with phosphorus pentasulfide in xylene gave compound 5 in 62% yield. The reaction of compound 3 with phosphorus pentoxide afforded compound 4 . Starting from hydrazide 11 , compounds 13 and 14 were prepared similarly. Reaction of compound 2 with substituted isothiocyanate yielded compound 9 which was cyclized in basic medium to 4-alkyl-5-(5-methyl-4-oxazolyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione ( 10 ). The isomer 19 was prepared similarly. Methylation and subsequent oxidation of compound 19 gave compound 21 . Reaction of the acid 7 with thiosemicarbazide in the presence of phosphorus oxychloride gave 2-amino-5-(5-methyl-4-oxazolyl)1,3,4-thiadiazole ( 8 ). 2-Amino-5-(4-methyl-5-oxazolyl)-1,3,4-thiadiazole ( 17 ) was prepared from acyl chloride 15 by the usual method.     

Unsaturated lactones

New, biologically active pyrazole derivatives containing an unsaturated -lactone ring were obtained by condensation of 2-(1-etboxycarbonyl-1,3-diketopropyl)-2-buten-4-olides with phenylhydrazine and hydrazine hydrate. A number of transformations of the resulting pyrazole-3-carboxylic acid esters were realized.See [1] for communication XXXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1611–1614, December, 1978.     

Methyl 3-cyclopropyl-3-oxopropanoate in the synthesis of heterocycles having a cyclopropyl substituent

Reactions of methyl 3-cyclopropyl-3-oxopropanoate with chloroacetone and ammonia, benzaldehyde and ammonia, and benzoquinone gave, respectively, methyl 2-cyclopropyl-5-methyl-1H-pyrrole-3-carboxylate, dimethyl 2,6-dicyclopropyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate, and methyl 2-cyclopropyl-5-hydroxy-1-benzofuran-3-carboxylate. Cyclization of methyl 3-cyclopropyl-3-oxopropanoate with ethyl chloro(arylhydrazono)ethanoates and other halohydrazones led to the formation of 3-substituted 1-aryl-5-cyclopropyl-1H-pyrazole-4-carboxylic acids, and 5-cyclopropyl-1-(quinolin-5-yl)-1H-1,2,3-triazole-4-carboxylic acid was obtained by reaction of the title compound with 5-azidoquinolines.     

Synthesis and properties of amides of 2-substituted 3-aryl- and 3-pyridylaminoacrylic acids

The reaction of aryl- or pyridylamines with ethyl orthoformate and malonanilic acid gave amides of 2-(N-arylcarbamoyl)-, 2-cyano-, 2-ethoxycarbonyl-3-arylaminoacrylic acids and their corresponding 3-pyridyl analogs. IR and PMR spectroscopy indicates that these compounds exist in the enamine form with strong intramolecular hydrogen bonds. Amides of 3-(2-pyridylamino)-2-ethoxycarbonylacrylic acid cyclize to give amides of pyrido[1,2-a]pyrimidine-3-carboxylic acid, which react with hydrazine hydrate to give amides of 3-aminopyrazole-4-carboxylic acid.Perm Pharmaceutical Institute, 614000 Perm. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–633, May, 1994. Original article submitted February 8, 1994.     

Functionalization of methyl 3-acetyl-5-[(methoxycarbonyl)amino]-2-methyl-1<Emphasis Type="Italic">H</Emphasis>-indole-1-carboxylate

Oxidative heterocyclization of methyl 3-{1-[2-(carbamoylhydrazinylidene)]ethyl}-2-methyl-5-[(methoxycarbonyl)amino]-1H-indole-1-carboxylate by the action of selenium dioxide in acetic acid and heating of the corresponding thiosemicarbazone in boiling acetic anhydride gave 1,2,3-selenadiazole and 2,3-dihydro-1,3,4-thiadiazole derivatives, respectively. Methyl 3-acetyl-2-methyl-5-[(methoxycarbonyl)amino]-1H-indole-1-carboxylate reacted with selenium dioxide in dioxane–water (30: 1) at 80?90°C to form methyl 5-[(methoxycarbonyl)amino]-2-methyl-3-(2-oxoacetyl)-1H-indole-1-carboxylate whose condensation with o-phenylenediamine afforded methyl 2-methyl-5-[(methoxycarbonyl)amino]-3-(quinoxalin-2-yl)-1H-indole-1-carboxylate.