(N‐heterocyclic carbene)PdCl(N‐heterocyclic carboxylate) complexes: Synthesis and catalytic activities towards arylation of benzoxazoles with aryl halides

A series of N‐heterocyclic carboxylate‐stabilized N‐heterocyclic carbene palladium complexes have been synthesized and fully characterized. The solid‐state structures indicate that each of the palladium centers is coordinated by an N‐heterocyclic carbene, a chloride and a bidentate N,O‐donor N‐heterocyclic carboxylate ligand. The catalytic performance of the complexes was screened and the results revealed that the complexes exhibit moderate to high catalytic activities for the direct C─H bond arylation of benzoxazoles with aryl bromides.     

Synthesis of pyrylium salts and pyridines containing heterocyclic substituents

A method of synthesizing pyrylium salts with heterocyclic substituents in the ring, has been investigated. The synthesis was carried out in two stages: alkaline condensation of aromatic and heterocyclic aldehydes with methyl ketones to give 1, 5-diketones, followed by cyclization to pyrylium salts by treatment with triphenylmethyl perchlorate. Pyridines containing heterocyclic substituents were obtained by treating the pyrylium salts with ammonia.     

过渡金属催化合成含氮杂环化合物的研究进展

含氮杂环化合物是一类非常重要的有机杂环化合物,也是有机合成化学的研究热点之一。本文首先简要介绍了含氮杂环化合物在天然产物、合成药物和功能材料中的分布及其广泛应用;然后以不同过渡金属催化剂为线索,按照时间由远至近的顺序分别概述了Pd、Ag、Fe、Ni、Zn、Cu等六类过渡金属催化剂在合成五、六元含氮杂环化合物方面的研究进展,对反应条件、反应特征进行了概括;最后对含氮杂环化合物合成领域的过渡金属催化剂的整体发展趋势进行了归纳总结。     

Synthesis of Novel [1,2,4]Triazolo[3,4-d][1,5] Benzodiazepinones Derivatives by 1,3-Dipolar Cycloaddition

Cycloaddition of N-aryl-C-ethoxycarbonylnitrilimines and diarylnitrilimines on 1,5-benzodiazepinones was achieved in a one-pot procedure, to give a variety of compounds possessing an additional heterocyclic ring fused to the heterocyclic nucleus. This reaction was revealed to be completely peri and regioselective. The structures were elucidated by spectral methods and X-ray crystallographic analysis.     

Preparation of Nitrogen Heterocycles of Spiro[Furo[2,3‐d]‐Pyrimidine]Pyrimidine Derivatives

Abstract

The NMR evaluation of the reaction progression of the bromination of heterocyclic dibarbiturates was used to develop an efficient synthetic procedure for the preparation of heterocyclic spiro[furo]pyrimidines. The structure of one of these compounds was confirmed by X‐ray analysis.     

The reaction of heteroaroyl‐substituted heterocyclic ketene aminals with 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl azide

The reaction of heteroaroyl‐substituted heterocyclic ketene aminals with 2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranosyl azide was investigated and a series of potential bioactive compounds, 1‐glucopyranosyl‐4‐heterocyclic‐5‐heteroaryl‐1,2,3‐triazoles, were obtained in good yields. Both the reaction rate and the yield were strongly affected by the heteroaryl and heterocyclic groups. In order to improve their water solubility, the deprotection of 1‐glucopyranosyl‐4‐heterocyclic‐5‐heteroaryl‐1,2,3‐triazole was carried out. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:242–247, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10023     

Blue Chitin Columns for the Extraction of Heterocyclic Amines from Urine Samples

During normal cooking of meat, a class of mutagenic/carcinogenic compounds called heterocyclic amines is formed. Heterocyclic amines are rapidly absorbed and metabolised in the human body, and for estimation of the intake of heterocyclic amines, it is useful to determinate their levels in the urine. Blue Chitin columns were used for the extraction and purification of heterocyclic amines from urine samples spiked with 14 different heterocyclic amines. The samples were analysed using LC-MS. The results show that Blue Chitin columns provide a straightforward and rapid means of extracting heterocyclic amines from urine samples, and that Blue Chitin column are also useful in the purification of urinary metabolites.     

Efficient Synthesis of Chromone and Flavonoid Derivatives with Diverse Heterocyclic Units

Chromones and flavonoids are important bioactive compounds. We envisioned that new heterocyclic‐substituted chromones or flavonoids might act as new bioactive compounds. To obtain diverse molecules, we developed an efficient one‐pot synthesis by Michael aldol reaction of chromone and flavonoid derivatives bearing heterocyclic units. The 2,3‐heterocyclic‐substituted chromones were obtained in one step. Moreover, the use of substituted benzaldehydes and subsequent addition of heterocyclic aldehydes gave 3‐pyridyl‐substituted flavones. We also examined these one‐pot reactions in the solid phase. To introduce an additional point of diversity into the molecules, Suzuki–Miyaura coupling was performed. Furthermore, we identified the cytotoxicity of the synthesized compounds against cancer cells (PANC1 and HeLa cells). Several compounds were cytotoxic to these cancer cells.     

Half-chair conformations of unsaturated heterocyclic compounds

The vicinal proton coupling constants were obtained for some 6-membered ring unsaturated heterocyclic compounds. The R values and ring dihedral angles were determined and found to be consistent with half-chair conformations. Relative to saturated heterocyclic compounds, the effect of the sulfur atom on ring puckering was attenuated. However, an increase in ring puckering resulted from the sulfone group and was attributed to torsional energy.     

Indium triflate-catalysed double addition of heterocyclic arenes to alkynes

Indium triflate was found to be a prominent catalyst for addition of heterocyclic arenes to alkynes to afford 2:1 adducts, where two heterocyclic arenes regioselectively attacked the same carbon atom of alkynes.     

Organic electrochemistry: Anodic construction of heterocyclic structures

The construction of heterocyclic frameworks constitutes one of the most dynamic and attractive branches in organic chemistry. Electrochemistry provides a versatile and powerful approach to assemble a heterocyclic skeleton. In this review, a selection of representative examples published during 2018–2019 are presented and discussed to showcase how to make use of anodic oxidation for the constitution of heterocyclic compounds.     

Toluene dioxygenase-catalyzed cis-dihydroxylation of benzo[b]thiophenes and benzo[b]furans: synthesis of benzo[b]thiophene 2,3-oxide

Enzymatic cis-dihydroxylation of benzo[b]thiophene, benzo[b]furan and several methyl substituted derivatives was found to occur in both the carbocyclic and heterocyclic rings. Relative and absolute configurations and enantiopurities of the resulting dihydrodiols were determined. Hydrogenation of the alkene bond in carbocyclic cis-dihydrodiols and ring-opening epimerization/reduction reactions of heterocyclic cis/trans-dihydrodiols were also studied. The relatively stable heterocyclic dihydrodiols of benzo[b]thiophene and benzo[b]furan showed a strong preference for the trans configuration in aqueous solutions. The 2,3-dihydrodiol metabolite of benzo[b]thiophene was utilized as a precursor in the chemoenzymatic synthesis of the unstable arene oxide, benzo[b]thiophene 2,3-oxide.     

Reactions of heteroaryllithium compounds with phosphorus trichloride,phosphorus oxychloride,and thionyl chloride. Formation of heterocyclic biaryls

The reactions of four equivalents of heterocyclic aryllithium compounds with phosphorus trichloride or phosphorus oxychloride gave symmetrical heterocyclic biaryls in good yields. A similar coupling was found in the reactions of three equivalents of the lithium compounds with thionyl chloride.     

Synthesis of Novel Quinazoline Derivatives as Antimicrobial Agents

Quinazoline isothiocyanate 1 reacts with various nucleophiles(nitrogen nucleophiles,oxygen nucleophiles and sulphur nucleophiles)to afford heterocyclic systemes 2-13,Also,the [4 2] cycloaddition reaction of 1 with phenyl isocyanate,benzylidene aryl amine and cinnamic acid derivatives gave novel heterocyclic compounds 14-16,Moreover,the reaction of 1 with active methylene compounds under Michael reaction conditions also was investigated to yield 17 and 18 and it was found that all these reactions proceede via isothiocyanate heterocyclization to furnish non-condensed heterocyclic compoundes,Some of the newly synthesized compounds were tested for their antimicrobial activities.     

Electrolytic partial fluorination of organic compounds: 89: Regioselective anodic fluorination of tetrazolyl sulfides

Anodic fluorination of five-membered nitrogen-containing heterocyclic sulfides like tetrazolyl sulfides was comparatively studied. The anodic fluorination of tetrazolyl sulfides having α-electron-withdrawing groups was successfully carried out to provide α-monofluorinated tetrazolyl derivatives in moderate yields. This is in sharp contrast to the low efficient anodic fluorination of triazolyl sulfides. Thus, it was found that the efficiency of anodic fluorination is greatly affected by the basicity of the heterocyclic groups of the starting heterocyclic sulfides.     

First palladium-catalyzed denitrated coupling of nitroarenes with sulfinates

The first example of palladium-catalyzed protocol for the denitrated coupling of nitroarenes with sulfinates was developed, achieving aryl and heterocyclic sulfones in moderate to excellent yields. The cyclopalladated ferrocenylimine (I) exhibited highly catalytic activity for this transformation with low catalyst loading (0.75 mol %). The efficiency of this reaction was demonstrated by compatibility with a wide range of groups. Thus, the method represents a simple and facile procedure to access aryl and heterocyclic sulfones.     

Synthesis of difluorinated β-ketosulfones and novel gem-difluoromethylsulfone-containing heterocycles as fluorinated building blocks

A series of new heterocyclic β-ketosulfides was prepared by the reaction of the corresponding heterocyclic thiols with α-bromoacetophenone and its derivatives. Oxidation of the products using m-CPBA gave the corresponding heterocyclic β-ketosulfones, which, on treatment with Selectfluor™ under anhydrous condition underwent electrophilic fluorination resulting in new heterocycles with difluoromethylene moiety adjacent to the sulfur atom and the carbonyl group. Base-induced cleavage of the five types of the resulting products, with different heterocyclic moieties as model compounds, afforded the difluoromethyl sulfones attached to the corresponding heterocycles. They can be considered as interesting fluorinated building blocks for further elaborations.     

Regioselective synthesis of fused ring heterocyclic derivatives of ketene aminals and their biological activities

A regioselective and convenient methodology was developed to synthesize heterocyclic derivatives, bearing imidazole, piperidines, and azepines rings. The N-arylnitrones derived from 3-formylchromones were selected to react with heterocyclic ketene aminal to furnish the structurally attractive and pharmacologically important fused ring heterocycles. The N-arylnitrone moiety of 3-formylchromone was used to activate the formyl group for regioselective fused ring heterocycles synthesis, whereas, the effect of substituents at aryl functionality of nitrones were studied to improve the yield of target fused ring heterocyclic products. The synthesized compounds (10-12) were evaluated for their in vitro cytotoxic and antifungal influences. In cytotoxic (brine shrimp lethality) assay, compound 11e was found to be active with LD₅₀ = 4.1 × 10⁻⁶ μg/mL.     

Synthesis of Sulfur-containing Heterocyclic Compounds Based on Isothiocyanate Derivatives of Perfluoroolefins. (Review)

The paper reviews data on the synthesis of heterocyclic compounds with perfluoroalkyl groups based on the reaction of thiocyanate and isothiocyanate derivatives of perfluoroolefins with mononucleophilic reagents (C-, O-, S-, P-, and N-nucleophiles). It was shown that such derivatives are prospective synthons for the production of 1,3-thiazoles and 1,3-thiazolines. The factors affecting the formation of the heterocyclic system are identified.     

Efficient Synthesis of Five Types of Heterocyclic Compounds via Intramolecular Elimination Using Ultrasound‐Static Heating Technique

An experimental technique, ultrasound‐static heating, has been developed for the efficient synthesis of heterocyclic compounds. The technique involves ultrasonic irradiation and static heating processes. First, the ultrasonic irradiation process is performed to form an intermediate of the heterocyclic compound under mild conditions and the subsequent static heating process (heating the intermediate under solvent‐free conditions without stirring) produces the target heterocyclic compounds via intramolecular elimination.