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Reactions heterocyclization

Nucleophilic reactivity of the sulfur atom has received most attention. When neutral or very acidic medium is used, the nucleophilic reactivity occurs through the exocyclic sulfur atom. Kinetic studies (110) measure this nucleophilicity- towards methyl iodide for various 3-methyl-A-4-thiazoline-2-thiones. Rate constants are 200 times greater for these compounds than for the isomeric 2-(methylthio)thiazole. Thus 3-(2-pyridyl)-A-4-thiazoline-2-thione reacts at sulfur with methyl iodide (111). Methyl substitution on the ring doubles the rate constant. This high reactivity at sulfur means that, even when an amino (112, 113) or imino group (114) occupies the 5-position of the ring, alkylation takes place on sulfiu. For the same reason, 2-acetonyi derivatives are sometimes observed as by-products in the heterocyclization reaction of dithiocarba-mates with a-haloketones (115, 116). [Pg.391]

A-2-Thiazoline-5-thiones are generally not obtained by direct heterocyclization reactions (352). Instead, most of the reported preparations involve reactions in which the thiazole ring is already formed with the suitable mercapto precursors in the 5-position. [Pg.416]

Thioacetyl derivatives (155) are obtained by direct heterocyclization reactions (365. 378, 563) and by a sulfur-oxygen exchange" reaction involving thioacetic acid and A-2-oxazoline-5-one (154) or A-2-thiazoline-5-one (156) (Scheme 81) (365, 378, 379). Ra-Ni reduction of 155 affords the 5-unsubstituted thiazole (379). [Pg.417]

In the heterocyclization reactions of 4-acetylenyl-l-methylpyrazole-3-carbox-ylic acids and 4-acetylenyl-l-methylpyrazole-5-carboxylic acids the behavior is the same. Isomeric l-methyl-4-phenylethynylpyrazole-3-carboxylic acid forms... [Pg.59]

As mentioned in the introduction, l-heterobut-l-en-3-ynes, RXCH=CHC=CH (X = RN, O, S R = organic radical), are the nearest and most important diacetylene derivatives readily formed by nucleophilic addition of amines, alcohols, and thiols to diacetylene. In many heterocyclization reactions (especially those leading to fundamental heterocycles) l-heterobut-l-en-3-ynes behave as diacetylene synthetic equivalents, but unlike diacetylene, they are nonhazardous. Therefore, the syntheses of heterocycles therefrom are often more attractive in preparative aspect. [Pg.183]

Comparison of the reactivity of conjugated ynaminocarbonyl compounds (N—C —C=0), their vinylacetylene analogs (N—C —C=C—C=0), and acetylenic ketones (C —C=0) in the heterocyclization reactions provides evidence for the highest activity of the former (92KGS867). [Pg.248]

Substituted derivatives of l-(tetrahydrobenzo[b]thiophen-2-yl-3-carboxylate)-5-phenyl-6-thio-l,2,4-triazin-4-one have been synthesized by heterocyclization reactions of different hydrazones obtained from 2-amino-tetrahydrobenzo[b]thiophene-3-carboxylate with phenyl isothiocyanate <00PS275>. Reaction of 5-methyl isothiosemicarbazide with a-amino acid vicinal tricarbonyl reactive substrates 1 and 2 yields 1,2,4-triazine substituted a-amino acids, as an equimolar mixture of regioisomers 3a/3b and 4a /4b, respectively <00JCS(P1)299>. [Pg.296]

I.3.4.2.2. Nonaromatic Unsaturated Heterocycles Reactions of aromatic nitrile oxides with 1-azirines are followed by the ring opening of the latter to give 4-benzamidoisoxazoles 145 (314). The structure of 145 (R = 4-C1C6H4, Ar = Ar7 = Ph) was established by single-crystal X-ray analysis. A mechanism for the formation of 145 has been proposed, (see Scheme 1.29). [Pg.49]

The program includes a few characteristic disconnections from the field of heterocyclic chemistry, which can be activated via the option "PROCESS-(heterocyclic chemistry)". These have only been included as examples. The Tables corresponding to these connections can be found in Appendix B-3. If the user really wants to use the CHAOS program in the field of heterocyclic chemistry, we suggest he/she should construct a heterocyclic reactions data base using the CHAOSBASE program. [Pg.460]

Keywords Continuous flow Heterocycles reactions Sustainable processes... [Pg.161]

The main difference of one other way of making tetramizole of the above described, consists of carrying out the heterocyclization reaction in the presence of sodium hydroxide instead of acetic anhydride, which makes the possible mechanism of the heterocyclization more understandable. In the suggested method, l-(2-phenyl-2-hydroxyethyl)-2-imino-l, 3-thiazolidine (38.1.28) is made by reacting styrene oxide with ethanolamine, and subsequent... [Pg.589]

The furoxan ring is notably resistant to electrophilic attack and reaction normally takes place at the substituents. Thus aryl groups attached to monocyclic furoxans and the homocyclic ring of benzofuroxans are nitrated and halogenated without disruption of the heterocycle. Reaction with acid is also slow protonation is predicted to occur at N-5 <89KGS1261> and benzofuroxans have pKj, values of ca. 8, similar to those of benzofurazans. Monosubstituted furoxans are, as expected, less stable and can be hydrolyzed to the corresponding carboxylic acid. Treatment of the parent furoxan (3) with concentrated sulfuric acid results in rearrangement to (hydroxyimino)acetonitrile oxide (HON=CHC=N —O ) and subsequent dimerization to bis(hydroxyiminomethyl)furoxan... [Pg.241]

In most of cases, the fluorine atom(s) or the CF3 group(s) is borne by aromatic rings. Synthesis of these compounds for the optimization of hits as well as for parallel synthesis is done using the numerous fluoro aromatic or heterocyclic compounds that are commercially available. These latter compounds generally come from aromatic fluorination or trifluoromethylation reactions (especially the Balz-Schiemann reaction) and from heterocyclization reactions. However, fluoroaliphatic chains and fluorofunctionalities are more and more present, because of their pharmacological properties. Some examples are given in this section. [Pg.339]

In the 1990s, the groups of Hiemstra and Larock independently discovered that Pd(OAc)2 in DMSO serves as an effective catalyst for direct dioxygen-coupled catalytic turnover, and this catalyst system was applied widely to oxidative heterocyclization reactions. Examples include the addition of carboxylic acid, phenol, alcohol, formamide, and sulfonamide nucleophiles to pendant olefins (Eq. 26) [146-149]. [Pg.96]

The intramolecular addition of carbon nucleophiles to alkenes has received comparatively little attention relative to heterocyclization reactions. The first examples of Pd-catalyzed oxidative carbocyclization reactions were described by Backvall and coworkers [164-166]. Conjugaled dienes with appended al-lyl silane and stabilized carbanion nucleophiles undergo 1,4-carbochlorination (Eq. 36) and carboacetoxylation (Eq. 37), respectively. The former reaction employs BQ as the stoichiometric oxidant, whereas the latter uses O2. The authors do not describe efforts to use molecular oxygen in the reaction with allyl silanes however, BQ was cited as being imsuccessful in the reaction with stabihzed car-banions. Benzoquinone is known to activate Ti-allyl-Pd intermediates toward nucleophilic attack (see below. Sect. 4.4). In the absence of BQ, -hydride eUm-ination occurs to form diene 43 in competition with attack of acetate on the intermediate jr-allyl-Pd" species to form the 1,4-addition product 44. [Pg.100]

The versatility of these [4+2] heterocyclization reactions is a consequence of the wide range of ene and diene components which can be used. In addition to alkenes and alkynes functioning as ene components, a variety of heterodienophiles is available such as electron-deficient imines (e.g. equation 89), nitriles e.g. equation 90), electrophilic carbonyl compounds (e.g. equation 91), thiocarbonyl compounds (e.g. equation 92), singlet oxygen (e.g. equation 93), nitroso compounds (e.g. equation 94), sulfenylsulfonamides (e.g. equation 95) and azo compounds (e.g. equation 96). Many of these reactions proceed with excellent regioselectivity and stereoselectivity, probably because in many instances they involve... [Pg.80]

From the material presented in this chapter one can conclude that the PTC methodology has already gained wide application in the chemistry of heterocyclic compounds. This is not surprising inasmuch as it offers extremely convenient conditions for a variety of heterocyclization reactions as well as for numerous modifications of heterocyclic molecules. Most of such reactions were or can be carried out under traditional conditions, but PTC usually increases the yields and purity of the products and provides a much simpler procedure for the reactions and for the isolations of the products. There are also many reactions that do not proceed satisfactorily unless conducted under PTC conditions. [Pg.233]


See other pages where Reactions heterocyclization is mentioned: [Pg.643]    [Pg.674]    [Pg.847]    [Pg.847]    [Pg.847]    [Pg.53]    [Pg.156]    [Pg.157]    [Pg.484]    [Pg.360]    [Pg.273]    [Pg.328]    [Pg.184]    [Pg.176]    [Pg.188]    [Pg.360]    [Pg.510]    [Pg.588]    [Pg.56]    [Pg.292]    [Pg.75]    [Pg.95]    [Pg.76]    [Pg.809]    [Pg.209]    [Pg.211]    [Pg.37]    [Pg.175]    [Pg.191]   
See also in sourсe #XX -- [ Pg.169 ]




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1.3- Dicyclohexylcarbodiimide heterocyclization reactions

2- Hydroxy-nitrogen heterocycles complexation reactions

Acetylenecarboxylic acids and esters, reactions with N-heterocyclic compounds

Acetylenecarboxylic acids, reactions with heterocyclic compounds

Acetylenecarboxylic esters, reactions with nitrogen-containing heterocycles

Acetylenecarboxylic esters, reactions with nitrogen-containing heterocycles through nucleophilic additions

Addition reactions heterocycles

Amide anion, reaction with heterocycles

Asymmetric Ring-Opening Reactions of Unsaturated Heterocycles

BENZOFUSED HETEROCYCLES VIA SOLID-PHASE SnAR REACTIONS

BENZOFUSED HETEROCYCLES VIA SOLID-PHASE SwAR REACTIONS

Benzyne, reactions with heterocyclic

Benzyne, reactions with heterocyclic compounds

Boranes, reaction with heterocycles

Bromine reaction with heterocycles

Butyllithium reaction with heterocycles

Carbenes and nitrenes in heterocyclic chemistry, intramolecular reactions

Carbenes, reaction with heterocyclic

Carbenes, reaction with heterocyclic compounds

Catalyst heterocycle reactions

Catalytic reactions involving heterocycles

Catalyzed Reactions of Aryl Halides with Heterocyclic Amines

Concerted reactions heterocyclic synthesis

Cope elimination reaction heterocyclic amines

Cross-coupling reactions heterocycles

Cross-coupling reactions with heterocycles, reviews

Cross-reactions heterocyclic ring

Cyanation reactions, heterocyclic

Cyanation reactions, heterocyclic compound

Cyclization reactions nitrogen heterocycles

Cycloaddition and Heterocyclization Reactions of Acetylenic Compounds with Electron-Withdrawing Substituents

Cycloaddition reactions heterocycles

Diacetylene and its derivatives heterocyclization reactions

Diazomethane, reactions with heterocycles

Diazomethane, reactions with heterocyclic

Diazomethane, reactions with heterocyclic compounds

Diazomethane, reactions with tautomeric heterocycles

Dichlorocarbene reaction with heterocycles

Diels-Alder reaction with aromatic heterocycles

Diels-Alder reaction with five-membered heterocycle

Electrolytic Reactions of Heterocyclic Systems

Elimination reactions heterocyclic synthesis, intramolecular Heck

Five-membered heterocycles 1,3-dipolar cycloaddition reactions

Five-membered heterocycles insertion reactions

Five-membered heterocycles reactions with carbenes

Five-membered ring heterocycles organic reactions

Fluorine and Perfluoroalkyl Groups into Five-Membered Heterocycles via Cyclocondensation Reactions

Formation of Heterocycles by Substitution Reactions

Free-radical reactions relative reactivities of heterocycles

Friedel-Crafts reaction With heterocycles

Heck reaction With heterocycles

Heck reaction heterocycles

Heck reaction heterocyclic carbopalladation

Heck reaction heterocyclic compounds

Heck reaction heterocyclic synthesis

Heck reaction with heterocyclic halides

Hetero Diels-Alder cycloaddition reactions synthesis of natural heterocyclic products

Hetero Diels-Alder cycloaddition reactions, synthesis of natural heterocyclic

Hetero Diels-Alder reaction heterocyclic synthesis

Heterocycle library synthesis multicomponent condensation reactions

Heterocycle library synthesis reactions

Heterocycle-forming reactions, categories

Heterocycles SrnI reaction

Heterocycles Through Cycloaddition Reactions

Heterocycles aromatic, reactions

Heterocycles cyclocondensation reaction

Heterocycles from cycloaddition reactions

Heterocycles from heteroatom Diels-Alder reactions

Heterocycles from oxazole rearrangements oxazoles reactions

Heterocycles halogen dance reaction

Heterocycles multi-component reactions

Heterocycles pyridine reactions

Heterocycles reaction

Heterocycles reaction

Heterocycles reaction with carbenes

Heterocycles reaction with carboxylic acids

Heterocycles reaction with organolithium reagents

Heterocycles saturated, reactions

Heterocycles sulfur containing, reactions

Heterocycles, acylation Diels-Alder reactions

Heterocycles, acylation radical reaction with

Heterocycles, acylation reaction

Heterocycles, reaction with compounds, literature

Heterocycles, reaction with literature reviews

Heterocycles, reaction with reviews

Heterocyclic aldehydes, reaction with

Heterocyclic aldehydes, reaction with amines

Heterocyclic amines, reactions

Heterocyclic arsenic compounds reactions

Heterocyclic chemistry Knoevenagel reaction

Heterocyclic chemistry Sonogashira reaction

Heterocyclic chemistry Wittig reaction

Heterocyclic chemistry, reaction mechanisms

Heterocyclic compounds 2 + 2)-cycloaddition and -cycloreversion reactions

Heterocyclic compounds 2 - cycloreversion reactions

Heterocyclic compounds Dieckmann reaction

Heterocyclic compounds Mannich reaction

Heterocyclic compounds Vilsmeier-Haack reaction

Heterocyclic compounds addition reactions

Heterocyclic compounds elimination reaction

Heterocyclic compounds halide reactions

Heterocyclic compounds intermolecular Heck reaction

Heterocyclic compounds intramolecular Heck reaction

Heterocyclic compounds reaction of acetylenecarboxylic acids

Heterocyclic compounds reactions

Heterocyclic compounds reactions of acetylenecarboxylic

Heterocyclic compounds reactions of diazomethane with

Heterocyclic compounds reactions of, with carbenes

Heterocyclic compounds reactions with arynes

Heterocyclic compounds reactions with hypochlorite

Heterocyclic compounds reactions with singlet oxygen

Heterocyclic compounds substitution reactions

Heterocyclic compounds synthesis via retro Diels-Alder reactions

Heterocyclic compounds, radical reactions

Heterocyclic coupling reactions with alkenyl bromides

Heterocyclic exchange reactions

Heterocyclic methylene-active carbonyl compounds, reaction

Heterocyclic nitramines derived from Mannich reactions

Heterocyclic products, natural, synthesis hetero Diels-Alder cycloaddition reactions

Heterocyclic products, natural, synthesis reactions

Heterocyclic reaction with diazonium

Heterocyclic synthesis alkene reactions

Heterocyclic synthesis diazoalkane cycloaddition reactions

Heterocyclic synthesis fullerene reactions

Heterocyclic transformation reactions, literature

Heterocyclizations Based on SNH Reactions

Insertion reactions five-membered heterocycle synthesis

Insertion reactions intramolecular, heterocycles

Intramolecular Oxidative Heterocyclization Reactions

Intramolecular carbolithiation reactions heterocycles

Intramolecular reactions forming heterocycles

Keto esters reaction with heterocycles

Knoevenagel reaction heterocycles

Maillard reaction, heterocyclic compounds

Mannich reaction heterocycles

Multicomponent reaction heterocyclic systems

N-Heterocyclic compounds reaction of acetylenecarboxylic acids

N-Heterocyclic compounds reaction of acetylenecarboxylic acids and

N-Heterocyclic compounds reaction of acetylenecarboxylic acids and esters with

N-heterocycles reactions

Name Reactions in Heterocyclic Chemistry

Name Reactions in Heterocyclic Chemistry II Edited by Jie Jack Li opyright

Name Reactions in Heterocyclic Chemistry-II Subject index

Natural heterocyclic products by hetero Diels-Alder cycloaddition reactions

Nitrogen heterocycles reactions of acetylenecarboxylic

Nitrogen heterocycles reactions of acetylenecarboxylic esters

Nitrogen heterocycles reactions of acetylenecarboxylic esters with

Nitrogen heterocycles reactions with acetylenic esters

Nitrogen heterocycles, saturated, reactions

Nucleophiles, reaction with aromatic heterocyclic bases

Of natural heterocyclic products by hetero Diels-Alder cycloaddition reactions

Other Reactions of Diazomethane with Heterocycles

Oxygen heterocycles, saturated, reactions

Oxygen-containing heterocycle reaction

Ozone reactions with heterocyclic compounds

Passerini reaction heterocycles

Polymer-supported reactions heterocyclizations

Radical reactions heterocyclic synthesis

Reaction Mechanisms in Heterocyclic Chemistry

Reaction Types Most Frequently Used in Heterocyclic Ring Synthesis

Reaction flavors heterocyclic compound formation

Reaction with heterocycles

Reactions Leading to the Formation of Heterocycles

Reactions from heterocyclic compounds

Reactions heterocyclic aromatic compounds

Reactions heterocyclic nitrogen atoms

Reactions of Coordinated Heterocyclic Ligands

Reactions of Five-Membered Heterocycles

Reactions of Heterocycles with Nucleophilic Radicals

Reactions of Heterocyclic Enamines

Reactions of N-Heterocycles in Transition Metal Complexes

Reactions of benzyne with heterocyclic compounds

Reactions of heterocycles

Reactions of heterocyclic nitrogen atoms

Reactions of saturated perfluorinated heterocycles

Reactions of substituents not directly attached to the heterocyclic ring

Reactions of substrates where tin is attached to a heterocyclic ring

Reactions of the Heterocyclic Ring

Reactions with Five-Membered Heterocyclic Rings

Reactions with Formation of Heterocyclic Compounds

Reactions with heterocyclic compounds

Reactions with sulfur heterocycles

Reissert reaction heterocycles

Replacement of NH2 in aromatic or heterocyclic compounds by fluorine (Schiemann reaction)

SYNTHESIS OF HETEROCYCLIC SYSTEMS BY CYCLOADDITION REACTIONS

Saturated five-membered nitrogen heterocycles reactions

Saturated heterocyclic aldol reaction

Side reactions heterocyclic synthesis, intramolecular

Sonogashira coupling reaction heterocycle synthesis

Sonogashira reaction heterocycle synthesis

Staudinger reaction heterocyclic synthesis

Stille reactions fused heterocycles

Strained heterocycles opening reaction

Sulfur heterocycles, saturated, reactions

Syntheses of Heterocycles, Natural Products, and Other Biologically Active Compounds Applying Heck Reactions

Synthesis of Nitrogen Heterocycles via Pd-Catalyzed 1,3-Dipolar Cycloaddition Reactions

Synthesis of natural heterocyclic products by hetero Diels-Alder cycloaddition reactions

Table of Contents for Volume 5 Name Reactions in Heterocyclic Chemistry

Tandem organic reactions heterocycle synthesis

Tandem reactions heterocycles

The Chemistry of Heterocyclic Compounds, Volume 60: Oxazoles: Synthesis, Reactions

The Reactions of Heterocyclic Compounds

Thermal Reactions in Heterocyclic Syntheses

Vinyl heterocycles, cycloaddition reactions

Vinyl heterocycles, cycloaddition reactions with

Vinyl heterocycles. Diels-Alder reactions

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