Electroreduction of 1-methyl 5-nitroindole, 5-nitrobenzofurane, and 5-nitrobenzothiophene in acidic and basic hydroorganic media: Generation and trapping of iminoquinone-type intermediates and electrosynthesis of ring-substituted amino derivatives

2003 ◽  
Vol 81 (10) ◽  
pp. 1108-1118 ◽  
Author(s):  
Luc Bouchard ◽  
Ian Marcotte ◽  
Jean Marc Chapuzet ◽  
Jean Lessard
Keyword(s):  
Key Words ◽  
Nucleophilic Addition ◽  
Acidic Medium ◽  
Cycloaddition Reaction ◽  
Am1 Calculations ◽  
Electrolytic Solution ◽  
Preparative Electrolysis ◽  
Regioselective Addition ◽  
Amino Derivatives ◽  
Type Intermediate

Preparative electrolysis of 1-methyl-5-nitroindole (1b, X = NCH3), 5-nitrobenzofurane (1c, X = O), and 5-nitrobenzothiophene (1d, X = S) at Hg, in acidic hydromethanolic media, leads to the formation of the corresponding 4-substituted amino derivatives 5, which result from the 100% regioselective addition to iminoquinone-type intermediate 4 of methanol or of any other good nucleophile present in the electrolytic solution. In acidic medium, the iminoquinonium intermediates 4b and 4c were trapped in a cycloaddition reaction with cyclopentadiene added to the electrolysis medium. The regiochemistry of the nucleophilic addition is discussed in light of AM1 calculations. Key words: 1-methyl-5-nitroindole, 5-nitrobenzofurane, 5-nitrobenzothiophene, iminoquinone, electrosynthesis.

Electrolytic reduction of o-nitrobenzyl thiocyanate in buffered solutions on mercury

1985 ◽  
Vol 50 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Jaromír Hlavatý
Keyword(s):  
Acidic Medium ◽  
Reaction Path ◽  
Electrolytic Reduction ◽  
Buffer System ◽  
Height Ratio ◽  
Preparative Electrolysis ◽  
Clear Explanation ◽  
Ec Mechanism ◽  
Controlled Potential

The o-nitrobenzyl thiocyanate (I) behaves differently on the DME and on a large mercury pool electrode. Polarography did not give a sufficiently clear explanation of the reaction mechanism, only the preparative experiments yielded useful results. Whereas polarographic curves in solutions of Britton-Robinson buffer system with 50% by vol. ethanol exhibit two cathodic waves within the pH region 1-12, corresponding according to their height ratio to an uptake of 4 e and 2 e respectively, the controlled potential preparation electrolysis (CPE) and coulometry results indicate a more complicated reaction path. In the CPE carried out at the concentration of I 1 . 10 -2 mol/l the electroreductive splitting of CH2-SCN occurs as the first step. Nitrobenzyl radicals so formed react in the follow-up dimerization resulting in dibenzyl or toluene structures. Simultaneously or at a later stage the completion of the electrolytic reduction of the nitro group proceeds to the hydroxylamino group. In solution of 9 > pH > 1 the CPE of nitro compound I takes place by an ECEC mechanism yielding dibenzodiazocine III, its N-oxide IV and 2,2'-dimethylazoxybenzene (V). In course of preparative electrolysis in strongly acidic medium 2-amino-benzo(l,3)-thiazine-l-oxide (II) is formed by an EC mechanism.

Réactivité nucléophile des cyclanones: influence de la stéréochimie cis/trans en série bicyclique

1982 ◽  
Vol 60 (18) ◽  
pp. 2355-2357 ◽  
Author(s):  
C. Agami ◽  
T. Rizk ◽  
R. Durand ◽  
P. Geneste
Keyword(s):  
Trans Isomer ◽  
Rate Constants ◽  
Nucleophilic Addition ◽  
Acidic Medium ◽  
Conformation Equilibrium ◽  
Bicyclic Ketones

The relative reactivities of a number of cis/trans pairs of bicyclic ketones in the 1- and 2-decalone series (2-decalone; 10-methyl-2-decalone; 9-methyl-1-decalone; and 3,10-dimethyl-2-decalone) have been studied for the nucleophilic addition of hydroxylamine in acidic medium. The results obtained as well as the rate constants for neutral or acid catalysed addition always reveal a slight preference for the trans-isomer (× 2.4). This result agrees with the proposal that preferential equatorial attack of a nucleophile is caused by conformational factors related to a steroid [Formula: see text] non-steroid conformation equilibrium in the cis-isomers. [Journal Translation]

The addition of alkynes to a tetrasilyldisilene — Evidence for a biradical intermediate

2005 ◽  
Vol 83 (9) ◽  
pp. 1568-1576 ◽  
Author(s):  
Stephen E Gottschling ◽  
Michael C Jennings ◽  
Kim M Baines
Keyword(s):  
Reaction Mechanism ◽  
Key Words ◽  
Cycloaddition Reaction ◽  
Major Product ◽  
Convincing Evidence ◽  
Mechanistic Probe

The addition of two newly developed mechanistic probes, (trans,trans-2-methoxy-3-phenylcyclopropyl)ethyne (1) and (trans,trans-2-methoxy-1-methyl-3-phenylcyclopropyl)ethyne (2), to tetrakis(tert-butyldimethylsilyl)disilene (3) has been investigated. The addition of 1 to 3 gave 1-[2-(cis-2-methoxy-3-phenylcyclopropylidene)vinyl]-1,1,2,2-tetrakis(tert-butyldimethylsilyl)disilane (5) as the major product; whereas addition of alkyne 2 to the disilene gave three stereoisomers of 1,1,2,2-tetrakis(tert-butyldimethylsilyl)-6-methoxy-5-methyl-7-phenyl-1,2-disilacyclohepta-3,4-diene (7–9) and 1,1,2,2- tetrakis(tert-butyldimethylsilyl)-3-(trans,trans-2-methoxy-1-methyl-3-phenylcyclopropyl)-1,2-disilacy-clobut-3-ene (10) as the major products. The formation of cycloheptaallenes 7–9 provides convincing evidence that the addition of alkynes to tetrasilyldisilenes involves the formation of a biradical intermediate. Key words: disilene, alkyne, cycloaddition, reaction mechanism, mechanistic probe.

One-pot four component domino strategy for the synthesis of novel spirooxindole pyrrolizine linked 1,2,3-triazoles via stereo- and regioselective [3 + 2] cycloaddition reaction in acidic medium

RSC Advances ◽  
2016 ◽  
Vol 6 (11) ◽  
pp. 9297-9303 ◽  
Author(s):  
Rajeswari M. ◽  
Sudesh Kumari ◽  
Jitender M. Khurana
Keyword(s):  
Acidic Medium ◽  
Mass Spectra ◽  
Cycloaddition Reaction ◽  
One Pot ◽  
X Ray ◽  
H Nmr ◽  
C Nmr

An efficient, one-pot four component condensation has been reported for the synthesis of spirooxindole pyrrolizine linked 1,2,3-triazolesvia[3 + 2] cycloaddition. The structures were confirmed by1H NMR,13C NMR, mass spectra and X-ray.

Controlled diastereoselection in 2-lithio-1,3-dithiane additions onto α-substituted γ-lactols. Model studies toward bryostatins from (R)-pantolactone

1991 ◽  
Vol 69 (1) ◽  
pp. 62-69 ◽  
Author(s):  
René Roy ◽  
Allan W. Rey
Keyword(s):  
Key Words ◽  
Absolute Configuration ◽  
Nucleophilic Addition ◽  
Major Product ◽  
Model Studies ◽  
Nuclear Overhauser Enhancement ◽  
The Absolute ◽  
Nuclear Overhauser ◽  
Very High

Homochiral α-substituted γ-lactols 3 and 4 derived from (R)-pantolactone 1 were used in 2-lithio-1,3-dithiane additions to afford very high controls in diastereoselectivities arising from 1,2-asymmetric inductions. Thus non-chelation controlled nucleophilic addition on 3 gave the anti diastereomer 5 as the major product (92% de), while the chelation controlled addition on 4 furnished the syn diastereomer 7 (96% de) as the almost exclusive product. The stereochemical outcomes of these reactions were proven unambiguously by locking the conformation of the syn- and anti-triol adducts 7 and 8 through their respective acetonides and by nuclear Overhauser enhancement measurements. The lack of 1,3-dioxolane formation in the case of the anti-triol 8 was taken as a further confirmation of the absolute configuration at the newly created stereocenter. Key words: byrostatin, pantolactone, α-hydroxylactol, dithiane.

Monohalogénocyclopropanation des esters et des acides α-éthyléniques diversement alkylés. Activation et stéréosélection antithermodynamique

1991 ◽  
Vol 69 (3) ◽  
pp. 489-495 ◽  
Author(s):  
Roger Barlet ◽  
Bahman Baharmast ◽  
Michel Vidal
Keyword(s):  
Double Bond ◽  
Key Words ◽  
Functional Groups ◽  
Stereoelectronic Effects ◽  
Unsaturated Alcohols ◽  
The Stability ◽  
Type Intermediate

The halogenocyclopropanation of α,β-unsaturated acids and their esters through a reaction with dichloromethane and MeLi/LiBr proceeds with excellent yields. With the esters, the only halogenocyclopropanic adducts obtained are the hydroxylated ones while the acids lead to carbonylated adducts as major products, even when there is an excess of MeLi. With the acids, the cyclopropanation takes place selectively with a lithiated hydrate of ketone type intermediate favouring the formation of the ring. The stability of the primary product of the cycloaddition is such that it does not react massively with the methyllithium and that the halogenocyclopropane ketones can be isolated after hydrolysis. With the esters, the reaction is also activated by the primary formation of an hemiacetal; however, the cycloaddition is more equilibrated between this intermediate and the alkoxide which results from the later action of the MeLi. In both cases, a net syn stereoselectivity is observed in the unsaturated alcohols in spite of the opposite steric and stereoelectronic effects operating when the alkyl and functional groups are in a cis relation around the double bond. Key words: halogenocyclopropanation, activation, syn stereoselectivity. [Journal translation]

Stereochemistry and kinetics of amines addition to acetylenic esters

1991 ◽  
Vol 69 (9) ◽  
pp. 1445-1449 ◽  
Author(s):  
Saber M. Sharaf ◽  
Samir K. El-Sadany ◽  
Ezzat A. Hamed ◽  
Abdel-Hamid A. Youssef
Keyword(s):  
Key Words ◽  
Nucleophilic Addition ◽  
Nmr Spectra ◽  
Acetylenic Esters ◽  
H Nmr ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Step Mechanism

The reactions of a series of methyl para-substituted phenylpropiolates 1a–e with piperidine, morpholine, and diethylamine in methanol and dimethylformamide (DMF) have been studied and their rates measured. The products were methyl β-(N,N-dialkylamino)-p-substituted cinnamates 2–4a–e. 1H NMR spectra were used to determine the configuration of the products. The ρ values in methanol ranged between 0.34 and 1.24 whereas in DMF they were between 0.85 and 1.88. The values of ΔS≠ favor a bimolecular rate-limiting step mechanism. Key words: nucleophilic addition to acetylenic esters.

Réactivité dipolaire-1,3 du 4,4,4-trichiloro-3-éthoxycarbonylamino-2-diazobutyrate d'éthyle issu de l'action du diazoacétate d'éthyle sur la N-éthoxycarbonyl-N-(2,2,2-trichloroéthylidène)amine

1997 ◽  
Vol 75 (5) ◽  
pp. 523-530 ◽  
Author(s):  
Abdelhak Belaissaoui ◽  
Sandrine Jacquot ◽  
Claude Morpain ◽  
Gérard Schmitt ◽  
Joël Vebrel ◽  
...  
Keyword(s):  
Nucleophilic Addition ◽  
Cycloaddition Reaction ◽  
Diazo Compound ◽  
Sigmatropic Rearrangement ◽  
Dipolar Cycloaddition ◽  
Acetylenic Esters ◽  
Ethyl Diazoacetate ◽  
Sigmatropic Rearrangements ◽  
Nitrogen Elimination ◽  
Substituted Pyrazoles

The reaction of ethyl diazoacetate with the N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine yields, by a nucleophilic addition, a new diazo compound that gives 1,3-dipolar cycloaddition reactions with acetylenic esters and maleimides. With acetylenic esters, the cycloadduct leads to substituted pyrazoles by [1,5] sigmatropic rearrangements. With maleimides, we observe a diastereospecific cycloaddition reaction. The intermediary cycloadduct evolves by nitrogen elimination to give a maleimidocyclopropane. The diastereospecificity was explained by an endo-anti approach of the reactants. Keywords: N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine, ethyl diazoacetate, nucleophilic addition, 1,3-dipolar cycloaddition, sigmatropic rearrangement, diastereoselectivity.

Synthesis of β-hydroxypiperidine alkaloids by anodic oxidation of carbamates and hydroboration

1996 ◽  
Vol 74 (12) ◽  
pp. 2444-2453 ◽  
Author(s):  
Mark Plehiers ◽  
Claude Hootelé
Keyword(s):  
Key Words ◽  
Anodic Oxidation ◽  
Nucleophilic Addition ◽  
Piperidine Ring ◽  
Anodic Methoxylation

The β-hydroxypiperidine alkaloids (±)-pseudoconhydrine, (±)-N-methylpseudoconhydrine, (−)-5-hydroxysedamine, and (+)-sedacryptine were synthesized. Successive functionalization of the piperidine ring via anodic methoxylation allowed the regio- and stereoselective introduction of the substituents. The α and α′ substituents were introduced by application of the sequence elimination–nucleophilic addition from 2- or 2,5-substituted 6-methoxycarbamates. Hydroboration – oxidation of enecarbamates, obtained by elimination of methanol from α-methoxycarbamates, allowed the introduction of the β-hydroxy function. Key words: alkaloid, Sedum, N-acyliminium, enecarbamate.

Stereoselective Synthesis of Tetrahydrofuran Lignans

Synthesis ◽  
2018 ◽  
Vol 50 (24) ◽  
pp. 4746-4764 ◽  
Author(s):  
Darunee Soorukram ◽  
Manat Pohmakotr ◽  
Chutima Kuhakarn ◽  
Vichai Reutrakul
Keyword(s):  
Intramolecular Cyclization ◽  
Nucleophilic Addition ◽  
Stereoselective Synthesis ◽  
Cycloaddition Reaction ◽  
Short Review ◽  
Furan Derivatives ◽  
Diastereoselective Hydrogenation ◽  
Naturally Occurring

This short review aims to summarize the reports on stereoselective synthesis of naturally occurring tetrahydrofuran lignans published during the period of 2006 to 2018. The stereoselective construction of non-natural tetrahydrofuran frameworks is not included in this review.1 Introduction2 Stereoselective Synthesis of 2,5-Diaryltetrahydrofuran (CL5-a)2.1 Synthesis of CL5-a via Friedel–Crafts Arylation or Nucleophilic Addition/Reduction of γ-Butyrolactones2.2 Synthesis of CL5-a via Intramolecular Cyclization of 1,4-Diaryl­butanediols2.3 Synthesis of CL5-a via Diastereoselective Hydrogenation of Furan Derivatives2.4 Synthesis of CL5-a via Cycloaddition Reaction of Substituted Cyclopropane­ Derivatives3 Stereoselective Synthesis of 2-Aryl-4-benzyltetrahydrofuran (CL5-b)4 Stereoselective Synthesis of 3,4-Dibenzyltetrahydrofuran (CL5-c)5 Conclusions

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