Catalyst-free Mannich-type reactions in water: Expedient synthesis of naphthol-substituted isoindolinones

An environmentally benign while efficient approach to the synthesis of isoindolinones by three-component reactions of 2-formylbenzoic acids, primary amines, 2-naphthols via a Mannich-cyclization reaction sequence in water under catalyst-free conditions is described here. This protocol features wide substrate scope, ease of operation, the use of naturally abundant while enviromentally benign water as a reaction medium and the formation of only water as the sole byproduct in the transformation.     

Solid-phase synthesis of heterocycles via palladium-catalyzed annulation

Solid-phase linked o-iodoanilines (4) and o-iodophenol (9) reacted with 1,3- and 1,4-dienes in the presence of palladium acetate to generate highly substituted indolines, tetrahydroquinolines, hydrobenzofurans and hydrobenzopyrans, which provided an efficient way for making heterocyclic molecule libraries.     

Sodium ethylene diamine tetraacetate catalyzed synthesis of chromene derivatives via multi-component reactions at low catalyst loading

Research on Chemical Intermediates - An efficient and practical protocol for the synthesis of chromenes derivatives catalyzed by a low-loading sodium ethylene diamine tetraacetate (2 mol%)...     

Catalyst-free,aqueous and highly diastereoselective synthesis of new 5-substituted 1H-tetrazoles via a multi-component domino Knoevenagel condensation/1,3 dipolar cycloaddition reaction

An approach for the synthesis of new 5-substituted-tetrazoles via multi-component domino Knoevenagel condensation/1,3 dipolar cycloaddition reaction of carbonyl compounds, malononitrile and sodium azide in water without assistance of any catalyst has been reported. This general protocol provides a wide variety of 5-substituted 1H-tetrazoles in good yields under mild reaction conditions.     

Efficient synthesis of diarylidene octahydroacridines by one-pot multi-component tandem reactions

A one-pot multi-component reaction is developed for the efficient synthesis of 4,5-dibenzylidene octahydroacridines in high yields. The reaction is performed by the tandem reaction of three molar equivalent aromatic aldehydes with two molar equivalent 4-alkylcyclohexanone in the system of NH₄OAc/HOAc under microwave irradiation.      

Catalytic synthesis and reactions of nitrogen heterocycles (Review)

Studies at the Latvian Institute of Organic Synthesis and literature data from 1984–1994 on organic catalysis in the chemistry of N-heterocycles are reviewed. 77 to prospects for further developments in catalytic reactions of N-heterocycles are examined.     

A review on multi-component green synthesis of N-containing heterocycles using mixed oxides as heterogeneous catalysts

The use of mixed oxides is a well-appreciated approach in the fields of material science and synthesis, due to remarkable tunable surface properties such as acidic and basic characteristics, oxidation/reduction capabilities, and high agility of lattice oxygen, which makes them ideal choices as heterogeneous catalysts. The activity of the mixed oxides broadly relies on the nature of support and active material used and on the preparation method, calcination temperatures. Wide range of techniques for preparation of mixed oxide materials are adoptable, viz. sol-gel, co-precipitation, wet impregnation, microwave irradiation and hydrothermal methods. Use of mixed oxides as solid catalysts have gained popularity in many valued organic transformations, via alkylation, oxidation, condensation, dehydration, dehydrogenation, cycloaddition and isomerization. Application of mixed oxides in the area of green organic synthesis is a valuable strategy, which contributed significantly to the design of many novel heterocyclic scaffolds. The chemistry of N-heterocycle scaffolds, which generally possess five and six membered rings, is an interesting area for both synthetic and medicinal chemistry research constituting over 60% organics used in various arenas. The position and number of nitrogen atoms in the rings, distinguish them as pyrroles, pyrazoles, imidazoles, triazoles, pyridines and pyramidines classes. In this review, we focus on the scope, importance and versatile applications of mixed metal oxides and their synergetic effects as heterogeneous catalysts in the synthesis of variety of N-heterocyclic derivatives. The scientific aspects of the mixed oxides as catalytic active materials to design efficient synthetic protocols for the organic transformations is also discussed.     

Efficient synthesis of useful heterocycles via transition metal-catalyzed cascade processes

This paper reports our recent results from synthesis of some useful heterocycles, for example oxazolidinones, indoles, and quinoxalinones, by transition metal-catalyzed cascade processes. The scope and limitations of these procedures and the reaction mechanism for formation of the heterocycles are also discussed.     

Recyclization reactions of heterocycles

The direction of recyclization during hydrazination of isoquinolinium salts is practically independent of the substituent attached to nitrogen and the reaction conditions and leads to compounds with an N-aminoisoquinoline structure.See [1] for communication XIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 961–965, July, 1974.     

Recyclization reactions of heterocycles

2,5-Dimethyl-1,3,4-oxa- and -1,3,4-thiadiazoles are recyclized to 2,5-dimethyl-4-amino-1,2,4-triazole on reaction with hydrazine. Recyclization occurs with greater difficulty and only with oxadiazole in the case of alkylhydrazines. Nitration of 2,5-dimethyl-4-amino-1,2,4-triazole gives its N-nitroamino derivative.See [1] for communication XVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 853–855, June, 1976.     

Recyclization reactions of heterocycles

2-Thioxo-4-oxazolidone and thiazolidines containing heteroatom substituants (O, S, and NH) in the 2 and 4 positions are converted to benzimidazole derivatives on reaction with o-phenylenediamine. The direction of these recyclizations depends on the nature of the heteroatom substituents in the 2 and 4 positions of the heteroring.See [1] for communication XX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 666–668, May, 1978.     

Catalyst-free three-component synthesis of hydroxyalkyltriazolylmethylidene barbiturates

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Sequential Ugi/Strecker reactions via microwave assisted organic synthesis: novel 3-center-4-component and 3-center-5-component multi-component reactions

Two novel one-step microwave mediated syntheses of arrays of 3-iminoaryl-imidazo[1,2-a]pyridines and imidazo[1,2-a]pyridyn-3-ylamino-2-acetonitriles are reported. Reactions are performed under microwave condition in methanol by simply mixing α-amino-pyridines, aldehydes, and trimethylsilylcyanide (TMSCN) with distinct reagent stoichiometries, catalyzed by polymer-bound scandium triflate, to afford either product. Furthermore, functionally different aldehydes were shown to proceed to different end-points, adding an extra caveat to the studies. The new methodology represents examples of both formal 3-center-4-component and 3-center-5-component multi-component reactions.     

Synthesis of biologically active phosphorus heterocycles via cyclization reactions of Lawesson's reagent

2,4‐Bis(4‐methoxyphenyl)‐1,3,2,4‐dithiaphosphetane‐2,4‐disulfide (Lawesson's reagent, LR) reacted with certain bifunctional compounds, such as glycinamides 1, 1‐glyceryl monoesters 4, and 3‐mercapto‐4‐amino‐5‐substituted‐1,2,4‐triazoles 6, to yield five‐membered phosphorus heterocycles 3,5, and 7, respectively. The cycloaddition reaction of LR with 1,3‐butadiene 8 was investigated to form the six‐membered heterocycle 9. The results of preliminary bioassays showed that these heterocycles obtained via cyclization reactions of LR possess significant selective herbicidal activity. The QSAR of 3 was also made. In conclusion, the cyclization reactions of LR with bifunctional substrates and 1,3‐dienes afford novel routes to the syntheses of biologically active phosphorus heterocycles. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 105–111, 1999     

Novel tandem multi-component reactions in the stereoselective synthesis of highly functionalised pyrrolidines

The four-component reaction of ethyl 4-chloroacetoacetate with aromatic aldehydes and ammonium acetate in a 1:2:1 molar ratio provided a simple and rapid access to highly functionalised pyrrolidines, ethyl 1-acetyl-4-hydroxy-5-[hydroxy(aryl)methyl]-2-aryl-2,3-dihydro-1H-pyrrole-3-carboxylates stereoselectively. This transformation presumably occurs via a tandem Mannich-substitution-acetylation-aldol sequence of reactions.     

Synthesis of functionalized carbo- and heterocycles via gold-catalyzed cycloisomerization reactions of enynes

The PPh₃AuCl/AgSbF₆ catalytic system promotes a tandem Friedel-Crafts' type addition of electron-rich aromatic and heteroaromatic derivatives to unactivated alkene followed by a C-C bond cyclization reaction. The efficiency of this system allowed room temperature reactions in a very short time. The scope and limitations of this reaction were investigated. The reaction conditions were compatible with various functional groups on the nucleophiles. Severe limitations were observed when the allylic position of the enyne is substituted by electron-withdrawing groups. The mechanism of the reaction was investigated via the synthesis of a deuterated aromatic ring: we showed that the source of proton involved in the protodemetallation step originates from the acidic activated C-H bond of the nucleophile.