Regioselective hydrodehalogenation of 3,5-dihaloisothiazole-4-carbonitriles: synthesis of 3-haloisothiazole-4-carbonitriles

3,5-Dibromoisothiazole-4-carbonitrile 1 treated with Zn or In dust (5 equiv) and HCO₂H undergoes regioselective hydrodebromination to give 3-bromoisothiazole-4-carbonitrile 3 in 70-74% yield. Similarly, 5-bromo and iodo 3-chloroisothiazole-4-carbonitriles 8 and 9 give 3-chloroisothiazole-4-carbonitrile 4 in 77 and 85% yields, respectively. Also hydrodeamination of 5-amino-3-chloroisothiazole-4-carbonitrile 7 using isoamyl nitrite gives the latter in 95% yield. The dibromoisothiazole 1 reacts with Zn dust in either DCO₂D or HCO₂D to give 3-bromo-5-deuterioisothiazole-4-carbonitrile 10 in 71 and 58% yields, respectively. The 3-bromoisothiazole 3 reacts with cyclic dialkylamines to give the corresponding 2-(dialkylaminomethylene)-malononitriles and not the expected 3-dialkylaminoisothiazole-4-carbonitriles. Finally, the 3-bromoisothiazole 3 is readily converted into both 3-bromoisothiazole-4-carboxamide 19 and the carboxylic acid 20. All products are fully characterized.     

Synthesis of 3,5-Diaryl-4-benzylideneamino-1,2,4-triazoles and 4-Amino-3,5-diaryl-1,2,4-triazoles

A one-pot reaction leading to 3,5-diaryl-4-benzylideneamino-1,2,4-triazoles is described, the key step of which is the reaction of arenecarbohydrazonoyl chloride with benzylidenehydrazide. Compounds obtained in this way were hydrolyzed to 4-amino-3,5-diaryl-1,2,4-triazoles.     

Regioselective synthesis of alkyl derivatives of 3,5-diamino-1,2,4-triazole

New procedures were suggested for regioselective synthesis of alkyl derivatives of 3,5-diamino-1,2,4-triazole.     

2,4-diazapenta-1,4-dienes in the synthesis of 2,6-diaryl-3,5-dinitropiperidines

2,4,6-Triphenyl-and 2,6-diaryl-3,5-dinitropiperidines were synthesized in 70–79% yields by reaction of 1,3,5-triaryl-2,4-diazapenta-1,4-dienes with 2,2-dimethyl-and 2-phenyl-1,3-dinitropropanes.     

Regioselective single-reactor synthesis of arylsulfonyl derivatives of 3,5-diamino-1,2,4-triazole

Arylsulfonylation of 1-acetyl-3,5-diamino-1,2,4-triazole with arylsulfonyl chlorides in pyridine, with the subsequent hydrolysis of the acetyl group, was studied; a new regioselective method for synthesis of N-(5-amino-1H-1,2,4-triazol-3-yl)arylsulfonamides was developed.     

An unexpected synthesis of 3,5-diaryl-1,2,4-thiadiazoles from thiobenzamides and methyl bromocyanoacetate

Aryl thioamides undergo very rapid condensation in the presence of methyl bromocyanoacetate to provide quantitative yields of 3,5-diaryl-1,2,4-thiadiazoles with an easy work-up and a high degree of product purity. The method can be scaled up with no loss in efficiency.     

Thermal fragmentation of 3,5-diaryl-1,2,4-oxadiazoles

3,5-Diaryl-1,2,4-oxadiazoles have been shown to undergo thermal fragmentation, and the pathway for the transformation is discussed.     

Regioselective synthesis of 1,5-diaryl-1H-imidazoles by palladium-catalyzed direct arylation of 1-aryl-1H-imidazoles

[reaction: see text] A variety of 1,5-diaryl-1H-imidazoles have been regioselectively synthesized by direct coupling of 1-aryl-1H-imidazoles with aryl iodides or bromides in DMF in the presence of CsF as the base and a catalyst precursor consisting of a mixture of Pd(OAc)2 and AsPh3. The data obtained in this synthetic study support a reaction mechanism involving an electrophilic attack of an arylpalladium(II) halide species onto the imidazole ring. Interestingly, some imidazole derivatives synthesized in this study have been found to exhibit significant cytotoxic activity against human tumor cell lines.     

A facile and convenient approach to the synthesis of 3,5-diaryl-1H-pyrazoles

A simple and convenient one-pot synthesis route is described for the synthesis of 3,5-diaryl-1H-pyrazoles in short reaction times from the reaction of α-epoxyketones with semicarbazide hydrochloride under mild conditions.     

A facile synthesis of 3,5-diaminopyrazole-4-carbothioamides and 3,5-diaminopyrazole-4-carboxylates

Simple and convenient synthesis of hitherto unknown 3,5-diaminopyrazole-4-carbothioamides 3 as well as new ethyl 3,5-diaminopyrazole-4-carboxylates 7 is reported. The key intermediates were 2-cyano-propenethioamides 2 and 2-(ethoxycarbonyl)propenethioamides 5 which were readily obtained by reaction of phenyl isothiocyanate with 3-(2-acylhydrazino)-3-aminopropenenitriles 1 and ethyl 3-(2-acylhydrazino)-3-aminopropenoates 4 respectively. Intramolecular cyclization of compounds 2 afforded pyrazole-4-carbothioamides 3 while propenethioamides 5 gave pyrazole-4-carboxylates 7 .     

Microwave-assisted synthesis of 4-amino-3,5-dihalopyridines

4-Amino-3,5-dihalopyridines have been efficiently prepared via microwave-assisted nucleophilic aromatic substitution of 3,4,5-trihalopyridines using 1-1.1 equiv of primary and secondary amines. The reaction is also applicable to electron rich arylamines.     

Synthesis and absorption spectra of 3,5-diaryl-1,2,4-triazoles

1,2,4-Triazoles with symmetrical tolyl substituents were obtained from the corresponding 1,3,4-oxadiazoles by reaction with formamide and subsequent hydrolysis of the resulting formyl derivatives; 1,2,4-triazoles with unsymmetrical substituents were obtained from iminoesters and hydrazides of acids. A set of bands of the triazole ring at 1470–1480, 1390, 1270–1290, 1140–1150, and 725–750 cm^–1 and of NH vibrations at 2400–3200, 1580–1620, and 830–900 cm^–1 are characteristic for the IR spectra of these triazoles. The UV spectra of the triazoles are characterized by phenyl ring absorption at about 200 nm and a band of electron transitions between the phenyl and triazole rings at 230–290 nm.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1685, December, 1977.     

Regioselective synthesis of N-substituted-4-substituted isothiazolidine-1,1-dioxides

A novel and efficient synthesis of a range of racemic and enantioenriched N-substituted-4-substituted isothiazolidine-1,1-dioxides from epoxides and sulfonamides is described. The critical choice of the activating group for the cyclization event is discussed. The application of this methodology to the synthesis of N-substituted-4,5-disubstituted derivatives is also described.     

Regioselective synthesis of 1-aryl-4-bromo-5-trifluoromethylpyrazoles

A novel regioselective route to 1-aryl-4-bromo-5-trifluoromethylpyrazoles involves reactions of arylhydrazines with 3-bromo-4-ethoxy-1,1,1-trifluorobut-3-en-2-one. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 167–168, January, 2006.     

(4-甲基-1,3-二噻烷-2-亚甲基)-1,7-二芳基-1,6-二烯-3,5-二酮的合成

从2,4-戊二酮和1,2,3-三溴丙烷出发合成了一类新的α-羰基二硫缩烯酮类化合物,并以其为底物合成了(4-甲基-1,3-二噻烷-2-亚甲基)-1,7-二芳基-1,6-二烯-3,5-二酮类化合物,通过IR和1H NMR方法对其进行了表征.