Heterocyclization of 2,4-disubstituted thiosemicarbazides with haloketones
TL;DR: In this paper, 2,4-disubstituted thiosemicarbazides were allowed to react with α-bromoacetophenone to give the anticipated 2,3-dihydro-6H-1,3, 4thiadiazines.
About: This article is published in Journal of Heterocyclic Chemistry.The article was published on 1990-03-01. It has received 33 citations till now.
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TL;DR: The molecular structures and spectral properties of α-haloketones as well as their syntheses are analyzed and reviewed in this paper, where their reactivity towards oxygen, nitrogen, and sulfur nucleophiles, carboxylic acids, carbon nucleophilic, alkenes, and alkynes are discussed.
Abstract: The molecular structures and spectral properties of α-haloketones as well as their syntheses are analyzed and reviewed. Their reactivity towards oxygen, nitrogen, and sulfur nucleophiles, carboxylic acids, carbon nucleophiles, alkenes, and alkynes are discussed.
166 citations
TL;DR: A systematic exploration of thiophilic ability of o-iodoxybenzoic acid (IBX) for oxidative desulfurization to trigger domino reactions leading to new methodologies for synthesis of different azoles is described.
Abstract: A systematic exploration of thiophilic ability of o-iodoxybenzoic acid (IBX) for oxidative desulfurization to trigger domino reactions leading to new methodologies for synthesis of different azoles is described. A variety of highly substituted oxadiazoles, thiadiazoles, triazoles, and tetrazoles have been successfully synthesized in good to excellent yields, starting from readily accessible thiosemicarbazides, bis-diarylthiourea, 1,3-disubtituted thiourea, and thioamides.
90 citations
TL;DR: A tandem and convergent approach to various N-, O-, or S-containing azoles has been developed by exploiting the thiophilic property of cop-per(I) iodide used in a catalytic quantity as mentioned in this paper.
Abstract: A tandem and convergent approach to var- ious N-, O-, or S-containing azoles has been devel- oped by exploiting the thiophilic property of cop- per(I) iodide used in a catalytic quantity. The present protocol gives access to amino-substituted tetrazoles, triazoles, oxadiazoles and thiadiazoles via oxidative desulfurization of their respective precursors fol- lowed by inter- or intramolecular attack of suitable nucleophiles. For aminotetrazoles and triazoles an excellent regioselectivity has been achieved through proper tuning of the pKa values of the parent amines attached to unsymmetrical thioureas. The method represents an autocatalytic process in which cop- per(I) iodide gets converted to copper(II) sulfide which in turn transforms to active copper(II) oxide that effectively carries forward the catalytic cycle. The fate of the copper catalyst has also been studied using scanning electron microscopic (SEM) and energy-dispersive X-ray spectroscopic (EDS) analy- ses which give an insight into the mechanism for this catalytic process.
50 citations
TL;DR: It is illustrated that many bioactive natural products containing pyridazine rings as a part of their molecules have been discovered and their structures determined and many new synthetic approaches and unusual transformations of pyrIDazines are described in the chapter.
Abstract: Publisher Summary This chapter provides an overview of further advances in pyridazine chemistry. The chapter illustrates that many bioactive natural products containing pyridazine rings as a part of their molecules have been discovered and their structures determined. Many new synthetic approaches and unusual transformations of pyridazines are described in the chapter. The chapter discusses other aspects, which have been the subject of intensive investigations, from a theoretical standpoint, of biological activities. With the resurgence of pyridazine derivatives as novel bioactive molecules these were the subject of intensive synthetic and medicinal studies. This chapter discusses the chemistry of pyridazine complexes with inorganic ions or compounds and their biological activities. Several pyridazine derivatives were prepared from haloalkyl or cyanoalkyl ketones. A great number of pyridazines can be prepared from preformed hydrazones or related compounds. Hydrazones of 1,2-diketones, when treated with ethyl cyanoacetate, can be transformed into cyanopyridazinones.
36 citations
TL;DR: Microwave and thermal heterocyclization of N,N′-disubstituted hydrazinecarbothioamide 1a,b and substituted thioureidoethylthiourea 6 are reported in this paper.
Abstract: Microwave and thermal heterocyclization of N,N′-disubstituted hydrazinecarbothioamide 1a,b and substituted thioureidoethylthioureas 2a–c as well as 1-phenyl-3[2-(3-phenylthio-ureido)phenyl]thiourea 6 are reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:535–541, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10188
30 citations
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TL;DR: In this article, a general method for the synthesis of 2,5 and 2,2,5-substituted 2,3-dihydro-1,3,4-thiadiazoles is described, involving the condensation of aldehydes or ketones with thioaroylhydrazines.
Abstract: A general method for the synthesis of 2,5- and 2,2,5-substituted 2,3-dihydro-1,3,4-thiadiazoles is described, involving the condensation of aldehydes or ketones with thioaroylhydrazines. Evidence for the cyclic nature of the products is discussed. The reaction of 4-methoxythiobenzoylhydrazine with β-chloropropiophenone gives 1-(4-methoxythiobenzoyl)-3-phenyl-4,5-dihydro-1H-pyrazole, whereas the corresponding reaction with α-chloroacetophenone gives the known compound 2-(4-methoxyphenyl)-5-phenyl-6H-1,3,4-thiadiazine. 4-Methoxybenzoylhydrazine also reacts with pentane-2,4-dione to give a mixture of 5-hydroxy-1-(4-methoxythiobenzoyl)-3,5-dimethyl-4,5-dihydro-1H-pyrazole and 2-acetonyl-5-(4-methoxyphenyl)-2-methyl-2,3-dihydro-1,3,4-thiadiazole, and with 4-oxo- and 5-oxo-alkanoic acids to give 2-(2-carboxyethyl)- and 2-(3-carboxypropyl)-5-(4-methoxyphenyl)-2-methyl-2,3-dihydro-1,3,4-thiadiazoles which are readily cyclized to 3-(4-methoxyphenyl)-5-methyl-4-thia-1,2-diazabicyclo[3.3.0]oct-2-en-8-one and 8-(4-methoxyphenyl)-6-methyl-7-thia-1,9-diazabicyclo[4.3.0]non-8-en-2-one.
26 citations
TL;DR: In this article, the rates of rearrangement were found to be first order with respect to the thiadiazine concentration and the rates decreased along the series in a manner characteristic of an SN2 reaction.
Abstract: The rates of rearrangement of the series 5-methyl-, 5-ethyl-, 5-isopropyl-, and 5-t-butyl-2-amino-1,3,4-thiadiazines in strong acid have been followed by observing the u.v. absorptions of the protonated thiadiazine substrates or the product thiazolimines. The rates of rearrangement were found to be first order with respect to the thiadiazine concentration and the rates decreased along the series in a manner characteristic of an SN2 reaction. The rates of rearrangement of 2-amino-1,3,4-thiadiazines with phenyl, p-nitrophenyl, and p-hydroxyphenyl groups in the 5 position were all extremely slow whereas 2-amino-5-benzyl-1,3,4-thiadiazine rearranged much faster than these arylthiadiazines but more slowly than the 5-methyl and 5-ethyl compounds. The rearrangement rates of 2-amino-5-methyl-1,3,4-thiadiazine were followed at various acid strengths within the range 4.47–8.12M-HCl. The reaction ultimately reached equilibrium, and the measured constant, k1, was equal to the sum of the velocity constants (kr+k–r) of the forward and backward reactions. Both kr and k–r were found to be similarly dependent on acidity and water activity. Using H0 values derived by Long and Paul with substituted anilines, a plot of log10k1 against –H0 was found to be linear and of slope equal to 0.92. A slope of –5.4 (w*) was obtained from the Bunnett plot of log10k1/CH+ against log10aw. A Yagil plot of log10k1/CH+ against log10Cw was linear and of slope equal to –2.95 at acidities less than 6.9M-HCl. Replacement of H by D at position 6 in all the thiadiazines was observed in D2O only in strong acid and D was incorporated both into the unchanged thiadiazine and the product thiazolimine (at position 5). A mechanism is suggested for the rearrangement which involves transannular nucleophilic atack by N(3) at an sp3 carbon atom in the 5 position of the thiadiazines.
22 citations
TL;DR: In this paper, 3.5-Halovalerophenones reacted with substituted thiosemicarbazides affording two different heterocyclic ring systems, hexahydro-1,3-dimethyl-8a-aryl [1,2,4]triazolo[1,5-a]pyridine-2(3H)-thiones.
15 citations
TL;DR: In this paper, the reactions of 4-alkyl-3-thiosemicarbazides with β-halophenones and o-halphenones gave 4,5-dihydro-N -alkyl -3-phenyl-1H-pyrazole-1-carbothioaraides, respectively.
10 citations
TL;DR: In this paper, the reactions of substituted thiosemicarbazides and γ-halobutyrophenones afforded derivatives of the tetrahydro-1H-pyrrolo[1,2-b][1, 2,4]triazole-2(3H)-thione ring system.
4 citations