Intramolecular cyclization of steroidal semicarbazones to pyrazoles using Vilsmeier reagent

The preparation of hitherto unknown steroidal heterocycles containing pyrazole fused to 6,7-position of the steroidal nucleus is described. These heterocycles were prepared by the action of Vilsmeier reagent with steroidal semicarbazones in DMF. The structure of the compounds has been established on the basis of their elemental analysis and spectral data. A general mechanistic scheme for these reactions is also suggested based on current and previous results.     

Synthesis of new heterocycles 1,3,2,6-dioxaphosphaselenacyclooctanes

New phosphorus- and selenium-containing heterocyclyes, 1,3,2,6-dioxaphosphaselena-cyclooctanes (la-1h), were synthesized by the reaction of bis(2-hydroxyethyl)selenide with RP(X)Cl2 where R=alkoxyl, aroxyl, aryl and X=O or lone pair. Their structures were determined by spectro-scopies and elemental analyses and finally confirmed by the X-ray crystallographic analysis of 1c. The molecular structures of the heterocycles were discussed in term of conformational analysis.     

Reactions with Hydrazidoyl Halides XII Synthesis of Pyrazolo[5,1-c]-1,2,4-triazine,Selenadiazolo[3,2-a]quinazolones,Selenadiazoline, Thiadiazoline and Thiazole Derivatives

Several new pyrazolo[5,I-c]triazine, selenadiazoline, thiadiazoline, selenadiazolo[3,2-a]quitiazolone, and arylazothiazole derivatives were synthesised by the reaction of hydrazonoyl halides with different reagents. The structure of new heterocycles were assigned on the basis of their elemental analysis, spectral data, and alternate synthesis whenever possible.     

N-Methylpiperidine assisted catalytic multicomponent reaction

Monatshefte für Chemie - Chemical Monthly - A catalytic methodology involving terminal alkynes, elemental sulfur, and three-membered heterocycles has been described. This domino transformation...     

3－苄基－6－（1－氨基烃基）－1，2，4－三唑并[3,4-b]-1,3,4-噻二唑的合成与波谱表征

3－苄基－4－氨基－5－巯基－1，2，4－三唑与氨基酸在三氯氧磷存在下反应 ，合成3－苄基－6－（1－氨基烃基）－1，2，4－三唑并[3,4-b]－1，3，4－噻二 唑，其结构经元素分析、红外光谱、核磁共振氢谱、碳谱、质谱等确证。这是稠杂 环接氨基酸残基的首次报道。     

1,3-双芳氧乙酰基-1,3,2-二氮磷杂环戊烷-2-硫(硒)代化合物的合成及除草活性研究

利用P(NEt₂)₃与双酰胺类化合物在干馏条件下的环缩合反应合成了一系列含双芳氧乙酰基的新型五元磷杂环,对所合成的化合物进行了元素分析和谱学表征.初步生物活性测定表明,部分化合物具有优良的选择性除草活性.合成中首次发现此类磷杂环的P⁼Se与P-Se的转化现象,通过X射线单晶衍射确证了产物的结构,并发现产物分子间氢键的存在     

GENERAL APPROACH TO THE SYNTHESIS OF SYMMETRICAL 1,3,2-DIAZAPHOSPHOCANES

Abstract

Synthesis of eight-membered phosphorus-nitrogen heterocycles has been performed by phosphocyclization of the corresponding diamines using different derivatives of phos horous acid. The structures of diazaphosphocanes were supported by elemental analysis; ¹H, ¹³C, and ³¹PNMR spectroscopy; and x-ray diffraction analysis.     

A Facile Synthesis of Novel Cyclic Esters of γ‐Keto Acid Derivatives by Heck Coupling Reaction

γ‐Keto acids and esters are highly useful compounds in organic synthesis, because a number of five‐membered carbocycles and various other heterocycles can be readily obtained from them. A number of γ‐keto acids derivatives have been synthesized with high yield by Heck coupling reaction with different alkenes using Pd(OAc)₂ as catalyst in dioxane solvent. The obtained products were characterized by elemental analysis, IR, proton NMR, and mass spectral studies.     

Open-air N-arylation of N–H heterocycles with arylboronic acids catalyzed by copper(II) Schiff base complexes

Two copper Schiff base complexes, in both homogeneous and heterogeneous forms, were prepared and characterized by using elemental analysis, FTIR, UV–Vis spectroscopy and scanning electron microscopy. The catalytic performances of these complexes were studied in the N-arylation of N–H heterocycles with arylboronic acids in methanol without any added base at 40 °C under open air. The effects of various parameters such as solvent and temperature on the reaction system were studied. The reaction is applicable to a wide variety of N–H heterocycles and arylboronic acids. The heterogeneous catalyst was recovered by simple filtration, and reusability experiments showed that this catalyst can be used five times without much loss in the catalytic activity.     

Efficient synthesis of 4-substituted pyrazole via microwave-promoted Suzuki cross-coupling reaction

Pyrazoles and their derivatives are important heterocycles found in nature and present in numerous bioactive compounds.In contrast to 3 or 5-aryl pyrazole,the preparation of 4-aryl pyrazole is fairly rare.Utilizing microwave irradiation,the synthesis of 4-substituted-arylpyrazole via Suzuki cross-coupling has been developed with a wide range of substrates.The remarkable advantages of this method are mild reaction conditions,simple operation,high yield,and short reaction time.Product structures were identified by MS 1H NMR 13C NMR,and elemental analysis.     

Novel small organo-P-S/Se heterocycles

Oxidative addition of elemental sulfur and selenium to cyclomonocarbatetraphosphines (PhP)4CR2 (R = H, Me) afforded novel five- and four-membered heterocycles PhP(E)CH2PhP(E)E2(E = S, Se) and PhP(Se)CMe2-PhP(Se)Se.     

Action of Some Nitrogen and Carbon Nucleophils on 4‐Arylidene‐1,3‐oxazolones

1,3‐Oxazolones 1 and 2 were reacted with hydrazine hydrate to afford the corresponding hydrazides 3 and 4 . Treatment of the hydrazides withacetylacetone, acetonylacetone, ethyl acetoacetate and diethyl malonateyielded different heterocycles. However, oxazolones 1 and 2 reacted with methyl p‐aminobenzoate to afford the imidazolones 5a , 5b which were converted into the hydrazide 3a or the triazinone derivative 6 upon treating with hydrazine hydrate. The structures of the newly synthesized compounds were established using IR, 1H‐NMR, EIMS, and elemental analyses.     

Building blocks for cyclotriveratrylene-based coordination networks

The incorporation of three-fold symmetric organic host molecules into coordination polymers should allow for the construction of new and interesting network structures, capable of multiple inclusion behaviour. A range of new multi-dentate bridging ligands/molecular hosts have been prepared by appending nitrogen-containing heterocycles to either cyclotricatechylene, or cyclotriguaiacylene cores. These compounds were obtained in a single-step reaction from readily available precursors, with moderate to good yields, and characterised by a combination of NMR spectroscopy, mass spectrometry and elemental analysis. Two of the new compounds were characterised by X-ray crystallography, revealing different modes of self inclusion behaviour, which indicate the potential importance of [small pi]-donor stabilisation by CTV derivatives in host-guest chemistry.     

Reactivity of 2‐Thiazolylhydrazonomalononitrile toward Carbon and Nitrogen Nucleophilic Reagents: Applications to the Synthesis of New Heterocycles

2‐Thiazolylhydrazonomalononitrile ( 1 ) was used as key intermediate for the synthesis of polyfunctionally substituted heterocycles (e.g. pyridazine, tetrazole, pyrimidines, 1,5‐benzo diazepine, benzoimidazo[1,2‐a]pyrimidine, triazolo[4,3‐a]pyrimidine, pyrazole, pyrazolo[1,5‐a]triazines, pyrazolo[1,5‐a]pyrimidine and 1,5‐benzoxazocine) incorporating thiazole moiety via its reactions with some carbon and nitrogen nucleophiles. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. The mechanistic aspects for the formation of the new compounds were also discussed.     

Synthesis and Structure of a 1‐Phospha‐2‐boraacenaphthene Derivative and Its Chalcogenation Reactions

The first stable 1‐phospha‐2‐boraacenaphthene 1 was synthesized by the reduction of 1‐dimesitylboryl‐8‐dichlorophosphinonaphthalene ( 2 a ) with elemental magnesium, and it was fully characterized. The chalcogenation reaction of 1 with elemental sulfur or selenium afforded the unique heterocycles, 2‐thia‐ and 2‐selena‐1‐phospha‐3‐boraphenalenes 9 S and 9 Se , respectively, through the insertion of the chalcogen atom into a P?B bond of 1 . Further chalcogenation of 9 afforded the corresponding phosphine chalcogenides. These newly obtained chalcogenated compounds have been characterized. The unique dynamic behavior of 2‐chalcogena‐1‐phospha‐3‐boraphenalene‐1‐chalcogenides 10 in solution has also been described.     

Facile access to some new 3,3′-bipyrazole-ester derivatives utilizing bis-hydrazonoyl chlorides

The 1,3-dipolar cycloaddition reaction of bis-hydrazonoyl chlorides with ethyl propiolate and dimethyl acetylenedicarboxylate afforded diethyl 1,1′-aryl-3,3′-bipyrazole-4,4′-dicarboxylate and tetramethyl 1,1′-diaryl-3,3′-bipyrazole-4,4′,5,5′-tetracarboxylate esters, respectively. Heating the latter two compounds with a mixture of HCl/AcOH furnished the same product: 3,3′-bipyrazole-5,5′-dicarboxylic acid. Reaction of the tetracarboxylate ester with aniline derivatives and with hydrazine gave the corresponding bipyrazole-fused heterocycles. Heating the dicarboxylic acid with 2-aminothiazole gave the corresponding bis-amide derivative. The structures of the products were established by elemental analysis, spectral data, and single-crystal X-ray crystallography.     

An Efficient Access to Pyrimidine‐based Polyfunctional Heterocycles with Anticipated Antibacterial Activity

6‐Amino‐2‐thioxotetrahydropyrimidine‐5‐carbonitrile derivative 2 was synthesized in a good yield via refluxing a mixture of arylidene 1 and thiourea in a highly basic sodium ethoxide solution. Subsequently, the synthesized pyrimidine‐2‐thione derivative 2 was allowed to interact with diversified nucleophiles and electrophiles under various reaction conditions in order to have a feasible access to further new and assorted fused heterocycles. Finally, the biological activity of the newly synthesized fused pyrimidines was screened in vitro against four different Gram‐positive and Gram‐negative bacterial strains. All the developed heterocycles were adequately characterized utilizing ¹H‐NMR, ¹³C‐NMR, Fourier transform infrared, elemental analysis, and electrospray ionization–mass spectrum and tested for their antibacterial activity.     

Efficient and Convenient One-Pot Synthesis of Dioxadiazaphophepines

The reaction of vicinal dioxime with sodium hydride in dry THF followed by addition of dichlorophosphates or dichlorothiophosphates yields 2-oxo-1,3,4,7-dioxadiazaphosphepines and 2-thioxo-1,3,4,7-dioxodiazaphosphepines in moderate to good overall yields. The products are characterized by elemental analyses, molecular weights and spectral (IR, ¹H, ¹³C and ³¹P NMR) studies. A salt elimination route is used for the synthesis of titled heterocycles.     

Synthesis and Photochromism of Novel Spiro(indoline-2,3'-naphtho[2,1-b][1,4]oxazine)

A series of novel spirooxazine(SPO) derivatives containing nitrogen heterocycles was synthesized and characterized by ¹H NMR spectra, Fourier transform infrared(FTIR) spectra, mass spectra(MS) and elemental analysis, and their photochromic behaviors were fully investigated in solvents and polymer media. In solvents, they displayed excellent photochromism properties such as high photochromic response and fast thermal bleaching rate. Especially, compounds 1 and 4 exhibited strong fluorescence intensities in dichloromethane solution. It was additionally found that compound 4 showed high fatigue resistence in poly(methyl methacrylate)(PMMA) film, and the thermal decay curves were fitted with biexponential function in PMMA film.     

Reactions of 5,7-Dichloro-4,6-dinitrobenzofuroxane and -furazane with Triphenylphosphine

Reactions of 5,7-dichloro-4,6-dinitrobenzofuroxane and 5,7-dichloro-4,6-dinitrobenzofurazane with triphenylphosphine proceed through a nucleophilic aromatic substitution of chlorine and nitro groups in the sixmembered ring of the heterocycles. The structure of the phosphorylation products was established from the IR, ³¹P NMR, and mass spectra and from XRD and elemental analysis. Schemes of the routes of the phosphorylation are discussed.