Cyclization of chalcones to isoxazole and pyrazole derivatives

A series of pyrazole and isoxazole derivatives were obtained by the condensation of the chalcones with hydrazine, phenylhydrazine, and hydroxylamine. All compounds were characterized using NMR, IR, and MS techniques.     

New synthesis of pyrazole and isoxazole derivatives

A convenient synthesis of 5-aryl-1-phenylpyrazoles and 5-arylisoxazoles, from readily available ketimine 1 dimethylformamide dimethylacetal and phenylhydrazine or hydroxylamine, is described.     

Mesogenic behaviour in some pyrazole and isoxazole derivatives

Abstract

Several aromatic β-diketones with a different number of alkyloxy groups in the aromatic rings and their derived pyrazoles, isoxazoles and thallium (I) complexes have been synthesized. The potential mesomorphic properties of these compounds have been investigated by optical microscopy, DSC and X-ray diffraction. The pyrazoles and isoxazoles with one chain in each aromatic ring are mesogenic, showing smectic A and smectic C mesophases, whereas the pyrazoles and isoxazoles with two chains per ring and the β-diketones and thallium complexes are not. The mesogenic potentiality is shown to be related to the molecular linearity and to the number of alkyloxy groups. To the best of our knowledge, this is the first time liquid crystal properties have been described for pyrazole and isoxazole derivatives.     

Mesogenic behaviour in some pyrazole and isoxazole derivatives

Several aromatic β-diketones with a different number of alkyloxy groups in the aromatic rings and their derived pyrazoles, isoxazoles and thallium (I) complexes have been synthesized. The potential mesomorphic properties of these compounds have been investigated by optical microscopy, DSC and X-ray diffraction. The pyrazoles and isoxazoles with one chain in each aromatic ring are mesogenic, showing smectic A and smectic C mesophases, whereas the pyrazoles and isoxazoles with two chains per ring and the β-diketones and thallium complexes are not. The mesogenic potentiality is shown to be related to the molecular linearity and to the number of alkyloxy groups. To the best of our knowledge, this is the first time liquid crystal properties have been described for pyrazole and isoxazole derivatives.     

A novel synthesis of 3-cyanoindoles and a new route to indole-3-carboxylic acid derivatives

2-Alkyl-3-cyanoindoles are obtained when 1-alkylmethyl-2-chloro-(or 2-phenylsulfonyl)-3-phenylsulfonylindoles are reacted with excess azide ion (90°/DMF). The reaction is considered to occur by a fragmentation recombination process in which the Schiff's base $\text{12}$ is of central importance. This proposal is supported by the formation of 2-substituted indole-3-carboxylates $\text{17}$ from aldehydes and the α-phenylsulfonyl-$\text{o}$-aminophenylacetic acid ester derivative $\text{16}$.     

A facile synthesis of 3-amino-5-substitutedaminoisothiazole-4-carboxylic acid derivatives

A facile, general and one-pot method for the preparation of 3-amino-5-substituted-aminoisothiazole-4-carboxylic acid derivatives, in high yields, by the aminative cyclization of 3-amino-3-mercaptoacrylonitriles is described.     

Synthesis and properties of derivatives of 4-aminofuroxan-3-carboxylic acid

4-Amino-3-cyanofuroxan, obtained by the oxidation of aminocyanoglyoxime, reacts with hydrazine and hydroxylamine to form the amidrazone and amidoxime respectively of 4-aminofuroxan-3-carboxylic acid. The reaction of the amidoxime with triethyl orthoformate can lead to closure of both the pyrimidine and the 1,2,4-oxadiazole ring.Latvian Institute of Organic Synthesis, Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1115–1119, August, 1997.     

Direct monobromination of substituted 4-oxoquinoline-3-carboxylic acid derivatives

N-Bromosaccharin in the presence of pyridinium poly(hydrogen fluoride) can be used for monobromination of ethyl esters of 6- and 7-substituted-4-oxo-1,4-dihydroquinoline-3-carboxylic acids. The reactions take place at the C₆ or C₈ positions, depending on the types and positions of the substituents.     

A new approach to 3-hydroxyquinoline-2-carboxylic acid

Quinoline-2-carboxylic acid derivatives cap the N-terminal of several natural cyclic peptides with antitumoral activity. A new and convenient route for the preparation of 3-hydroxyquinoline-2-carboxylic acid is discussed. The preparation of the title compound is accomplished by a four-step procedure from 3-hydroxyquinoline via MOM protection of the hydroxyl group, followed by a 1,2-addition of methyllithium to the quinoline ring with concomitant oxidation, and, finally, a two-step oxidation procedure for the transformation of the methyl group to the carboxylic acid along with removal of the MOM group. Furthermore, different attempts to its preparation led to other interesting quinolines, such as 2-chloro-3-hydroxyquinoline-4-carboxylic acid and a protected 3,3′-dihydroxy-2,2′-biquinoline.     

A general approach to indole-7-yl derivatives of isoxazole, oxadiazole, thiadiazole and pyrazole

Isosteric replacement of the α,β-unsaturated amide at the C-7 position of indoles with a diverse set of five-membered amino-heterocycles including isoxazole, oxadiazole, thiadiazole and pyrazole followed by subsequent derivatization of the heterocyclic amino group to yield amides, sulfonamides and phosphoramides is described. Distinctive features of these procedures include the versatility and robust nature of the synthetic steps along with the high yields of the targeted molecules.     

Directed metallations of 4-ethylidenetetronic acid and its derivatives as a synthetic entry to natural 4-oxy-2-furanones

Lithium diisopropylamide (LDA) removes the α-proton from the O-methyl tetronic acid (2$\text{b}$) leading to the vinylic carbanion (12), whereas treatment of the trimethylsilyl derivative (14) with LDA, followed by reaction with aldehydes gives products resulting from both γ? and ε-addition; the directed metallations provide access to a range of 4-oxy-2-furanone derivatives found amongst natural products.     

Synthesis of new fungicidal biphenyl derivatives of 4,5-dichloroisothiazole-3-carboxylic acid

Methods have been developed for the synthesis of new 2,4,4′-substituted biphenyl derivatives containing 4,5-dichloroisothiazole-3-carboxamide and 4,5-dichloroisothiazole-3-carboxylate fragments. The synthesized compounds showed pronounced fungicidal activity.     

Synthesis of new acridine-9-carboxylic acid derivatives

New 1,3-dihydroxyacridine-9-carboxylic acids were obtained by Pfitzinger reaction from 2,4,6-trihydroxytoluene (methylphloroglucinol). Their bromination and azo-coupling reactions were studied. Computer simulation was used to determine potential pharmacokinetic and toxic properties of the synthesized compounds.     

Synthesis of quinoline-4-carboxylic acid and its derivatives

2-Methylquinoline-4-carboxylic acid was obtained by the reaction of isatin with acetone in the presence of an alkali. This acid was converted through a step involving (E)-2-styrylquinoline-4-carboxylic acid to quinoline-2,4-dicarboxylic acid, from which quinoline-4-carboxylic acid was obtained by refluxing in nitrobenzene. The structures of the synthesized compounds were confirmed by ¹H NMR spectroscopy using two-dimensional (2DJ) spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 819–821, June, 1988.     

Synthesis of furoxan derivatives based on 4-aminofuroxan-3-carboxylic acid azide

A convenient preparative method was developed for the synthesis of 4-amino-3-furoxancarboxylic acid azide, which is a universal synthon for the preparation of functional furoxan derivatives. This method was used for preparing new azo-, azoxy-, azido-, cyano-, nitro-, carbonylamino-, and hydroxylamino-substituted furoxan derivatives, which have earlier been difficultly accessible.     

Convenient synthesis of furan-3-carboxylic acid and derivatives

A convenient synthesis of furan-3-carboxylic acid and derivatives from aromatization of 4-trichloroacetyl-2,3-dihydrofuran followed by nucleophilic displacement of the trichloromethyl group by hydroxide, alcohols, and amines, is presented.     

Synthesis of new 3,3-dimethoxyazetidine-2-carboxylic acid derivatives

Cyclization of γ-amino-α-bromocarboxylic esters resulted in an efficient synthesis of new 3,3-dimethoxyazetidine-2-carboxylates, that is, methyl N-t-butyl-3,3-dimethoxyazetidine-2-carboxylic ester and 3,3-dimethoxyazetidine-2-carboxylic acid, or 3-bromo-4,4-dimethoxypyrrolidin-2-ones, depending on the substituent at nitrogen. Reduction of the 3,3-dimethoxyazetidine-2-carboxylates gave the corresponding 3,3-dimethoxy-2-(hydroxymethyl)azetidines. These novel cyclic amino acid derivatives, available on multigram scale, have a suitably protected carbonyl function at the 3-position, which enables further functionalization.     

Synthesis and transformations of new 3-oxo(thioxo)-1-phenyl-2,3,5,6,7,8-hexahydroisoquinoline-4-carboxylic acid derivatives

By condensation of 2-benzoyl-1-(morpholin-4-yl)-1-cyanohexene with cyanoacetanilides and monothiomalonodiamide the corresponding 2-substituted 3-oxo-1-phenyl-2,3,5,6,7,8-hexahydroisoquinoline-4-carbonitriles and 3-thioxo-1-phenyl-2,3,5,6,7,8-hexahydroisoquinoline-4-carboxamide were obtained. The latter was used in the synthesis of 3-alkylthio-1-phenyl-5,6,7,8-hexahydroisoquinoline-4-carboxamides and 3,3-dimethyl-1-oxo-6-phenyl-1,2,7,8,9,10-hexahydro-3H-[1,3]thiazino[6,5-c]isoquinoline.