In this paper, a high‐yield, facile route for the scalable synthesis of sulfonyl 2‐aroylbenzofurans via a Bi(OTf)3‐mediated intermolecular double cyclocondensation of α‐sulfonyl ...o‐hydroxyacetophenones with substituted α‐hydroxy arylketones under mild open‐vessel reaction conditions is described. In the overall reaction, water is generated as the only byproduct. Various metal triflate‐promoted reactions and conditions are investigated for the efficient one‐pot (4+1) annulation reaction.
The cyclocondensation of the bielectrophile 2,3-bis(bromomethyl)-1,4-dimethoxyanthracene-9,10-dione with several heteroyl-benzyl hydrazides with the formation of exofunctionalized tetracyclic quinoid ...systems was studied. Different numbers of products were isolated by liquid chromatography for different hydrazides. The products were identified as atropisomers. Generally, only one isomer was isolated for N'-(4,6-dimethylpyrimidin-2-yl)benzohydrazide, while two and three isomers were isolated for N'-(6-chloropyridazin-3-yl) benzohydrazide and for N'-(4-chlorophthalazin-1-yl) benzohydrazide, respectively. To determine their structure, modeling of the geometries and NMR spectra by DFT methods was performed. The structure of the obtained isomers was established based on 1H, 13C NMR and NOESY spectra, the results well agree with the simulation results.
Vilsmeier-Haack formylation of 3-acetyl-4-hydroxycoumarin (1) afforded the unexpected 3-chloro-3-(4-chlorocoumarin-3-yl)prop-2-enal (3). Compound 3 reacted with p-toluidine and benzylamine producing ...Schiff base 4 and enamine 6, respectively. Treatment of compound 3 with hydrazine hydrate produced bis-coumarin 15 which upon treating with hydrazine hydrate afforded bis chromeno4,3-cpyrazole derivative 16. Compound 3 reacted with cyanoacetohydrazide under different conditions. Condensation of compound 3 with some heterocyclic amines and 1,2-N,N-binucleophiles was studied. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.
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Tetrasubstituted 1H‐imidazoles are a large family of heteroarene derivatives that are known to include natural products isolated from marine sponges and synthetic compounds possessing a broad range ...of biological and pharmacological properties. Consequently, a great deal of attention has been given to the synthesis of these heteroarenes and reviews covering some synthetic aspects of this topic have been published in recent years. However, none of these reviews provides a comprehensive overview of the catalytic methods developed in the literature for the preparation of this important class of heteroarenes. This article aims to provide an updated critical picture of the catalytic processes reported in the literature up to the end of 2017 for the synthesis of 1,2,4,5‐tetrasubstituted 1H‐imidazoles illustrating these protocols and their characteristic features such as scope, efficiency, versatility, and limitations. The review also summarizes the mechanisms proposed for many of the reported processes.
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•A pair of natural isomeric naphthoxanthenones were prepared with efficiency and in the mmol scale.•Cyclocondensation and Buchwald hydroxylation were implemented as key steps.•The ...compounds show DNA-intercalation ability.
5-methoxy-1H-naphtho2,1,8-mnaxanthen-1-one (1) and 5-methoxy-3H-naphtho2,1,8-mnaxanthen-3-one (musafluorone 2), a pair of positional isomers isolated from Wachendorfia thyrsiflora and Musa acuminata, were synthesized in six steps in an overall yield of 53% and 59% starting from the corresponding methoxyphenalenones and employing an acid mediated cyclocondensation strategy. Preliminary assays demonstrated the intercalation ability of compounds 1 and 2 into DNA.
o-Aminoaldehyde 1 was employed as starting precursor for construction of some linear heterocyclic compounds. o-Aminoaldehyde 1 was permitted to undergo Friedländer reaction with some acyclic and ...cyclic methylene ketones giving the novel annulated heterocyclic systems 2-10. Moreover, the reactivity of o-aminoaldehyde 1 was examined toward some cyclic enamines and enols producing the corresponding annulated heterocyclic systems. The prepared compounds were investigated for their antimicrobial efficiency displaying different inhibition action toward the tested microorganisms. Based on analytical spectral and results, structures of the produced compounds were established.
Background. Wood is a unique material in its structure. However, materials made from wood raw materials have such negative properties as insufficient bio- and fire-resistance. In turn, when ...organizing and improving the efficiency of logging activity, large amounts of practically unused cutting residues is produced. Their modification for the purposes of the forest industry is an effective tool for creating many valuable and demanded products. In particular, arilazo-β-dicarbonyl compounds are widely used as syntons for the production of heterocyclic compounds. Among heterocycles, a large number of compounds have found application in the form of biologically active substances that have been successfully and for a long time used as pesticides for the wood processing industry. Purpose. Synthesis of p-nitrophenyl hydrobutanons, cyclocondensation to form pyrazoles and study of their chemical properties of the substances first obtained. Proof of structure by modern spectral analysis methods. Materials and Methods. Research methods include: organic synthesis; UV spectrometry, 1H NMR, 13H NMR. Results. Four new compounds were synthesized: 4-methoxy-1-(p-chloro(bromo)phenyl)-2-(p-nitrophenylhydrazo)-1,2,3-butantrions and 3(5)-methoxy-5(3)-(p-chloro(bromo)phenyl)-4-(p-nitrophenylhydrazo)-1H-pyrazoles. Amines were prepared by the reduction of the related nitrosopyrazoles. The acylation reaction was demonstrated for the obtained amine. The structures of all synthesized compounds were proved by modern methods of analysis. Conclusion. Thus, we synthesized p-nitrophenylhydrazobutanetriones with a chloro(bromo)phenyl substituent, their cyclization products with hydrazine, and N-(5-(4-chloro(bromo)phenyl)-3-(methoxymethyl)-1H-pyrazole-4-yl)acetamides based on them. The structure of the obtained substances was determined by spectral methods of analysis.
•Cyclocondensation of 2-aminopyrazine under aqueous hydrochloric acid medium.•A cyclocondensation of a diazine-based compound.•Polycyclic compound with fused six-membered rings.•Crystal structure and ...geometric analyses (Mogul) of the polycyclic compound.•B3LYP/6-311G optimization of the polycyclic compound corroborating its structural assignment.
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Aromatic compounds are well-known due to their stability, and this efficiently provides several applications. However, this does not indicate low reactivity for every condition. For instance, electrophilic substitution reactions are widespread and easily performed. Otherwise, reactions that induce the loss of aromaticity, such as condensed cyclizations are uncommon. These last types of reactions typically occur under severe conditions, under heat influx and high pressure. Here we report the formation of a dihydrochloride salt monohydrate of an ionic polycyclic compound bearing a four fused six-membered rings motif. This complex compound was obtained by the simple reaction of 2-aminopyrazine with hydrochloric acid in an aqueous medium at room temperature. Crystal data and DFT calculations could confirm the cyclocondensation of 2-aminopyrazine.
tBuONa‐catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o‐thio/hydroxy/aminoanilines under air have been developed and provide an efficient, practical, ...and green method for the synthesis of benzazoles. Mechanistic studies revealed that o‐substituted anilines promote the initial aerobic alcohol‐oxidation step, which explains the high reactivity and success of this unexpectedly simple and practical cyclocondensation method.
Simple and straight: tBuONa‐catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o‐thio/hydroxy/aminoanilines under air provide an efficient, practical, and green method for the synthesis of benzazole heterocycles (see scheme). Mechanistic studies revealed that o‐substituted anilines promote the initial aerobic alcohol‐oxidation step.
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