Driving force due to electron-releasing groups on the double bond in the solvolytic ring closure of unsaturated arenesulphonates

1968 ◽  
pp. 60 ◽  
Author(s):  
Hugh Felkin ◽  
Claude Lion
Keyword(s):  
Double Bond ◽  
Driving Force ◽  
Ring Closure

scholarly journals A biomimetic approach to some specifically functionalized cyclic terpenoids.

2007 ◽  
Vol 54 (4) ◽  
pp. 679-693 ◽  
Author(s):  
Veaceslav Kulciţki
Keyword(s):  
Double Bond ◽  
Functional Groups ◽  
Ring Closure ◽  
Living Systems ◽  
Open Chain ◽  
Initial Substrate ◽  
Alpha Omega ◽  
Biomimetic Approach

The paper relates on the current advancements in the synthesis of complex cyclic terpenoids by superacidic induced cyclization of open chain precursors. It is shown that functional groups disposal in the initial substrate strongly influences the reaction outcome. Possible variations of the investigated compound structures include particularly alpha-functionalization and alpha,omega-bifunctionalization. This approach allowed a selective initiation of cyclization sequence from an internal double bond or suspending the ring closure cascade to partially cyclized compounds. The reported synthetic schemes are attempts to mimic the biogenetical processes postulated in the living systems.

scholarly journals Ring-Closing Metathesis Approaches towards the Total Synthesis of Rhizoxins

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4527
Author(s):  
Marc Liniger ◽  
Christian M. Neuhaus ◽  
Karl-Heinz Altmann
Keyword(s):  
Double Bond ◽  
Total Synthesis ◽  
Triple Bond ◽  
High Selectivity ◽  
Growth Inhibitor ◽  
Direct Conversion ◽  
Ring Closure ◽  
Side Chain ◽  
Alkyne Metathesis ◽  
Cancer Cell Growth

Efforts are described towards the total synthesis of the bacterial macrolide rhizoxin F, which is a potent tubulin assembly and cancer cell growth inhibitor. A significant amount of work was expanded on the construction of the rhizoxin core macrocycle by ring-closing olefin metathesis (RCM) between C(9) and C(10), either directly or by using relay substrates, but in no case was ring-closure achieved. Macrocycle formation was possible by ring-closing alkyne metathesis (RCAM) at the C(9)/C(10) site. The requisite diyne was obtained from advanced intermediates that had been prepared as part of the synthesis of the RCM substrates. While the direct conversion of the triple bond formed in the ring-closing step into the C(9)-C(10) E double bond of the rhizoxin macrocycle proved to be elusive, the corresponding Z isomer was accessible with high selectivity by reductive decomplexation of the biscobalt hexacarbonyl complex of the triple bond with ethylpiperidinium hypophosphite. Radical-induced double bond isomerization, full elaboration of the C(15) side chain, and directed epoxidation of the C(11)-C(12) double bond completed the total synthesis of rhizoxin F.

scholarly journals Novel stereocontrolled syntheses of tashiromine and epitashiromine

2015 ◽  
Vol 11 ◽  
pp. 596-603 ◽  
Author(s):  
Loránd Kiss ◽  
Enikő Forró ◽  
Ferenc Fülöp
Keyword(s):  
Amino Acids ◽  
Double Bond ◽  
Ring Opening ◽  
Ring Closure

A novel stereocontrolled approach has been developed for the syntheses of tashiromine and epitashiromine alkaloids from cyclooctene β-amino acids. The synthetic concept is based on the azetidinone opening of a bicyclic β-lactam, followed by oxidative ring opening through ring C–C double bond and reductive ring-closure reactions of the cis- or trans-cyclooctene β-amino acids.

Novel Ring Closure Carbonylation Reaction of 1,5-Cyclooctadiene in the Presence of Pd(II)-Catalysts

1992 ◽  
Vol 57 (11) ◽  
pp. 2374-2382 ◽  
Author(s):  
Curtis B. Anderson ◽  
Rade Marković
Keyword(s):  
Carbon Monoxide ◽  
Double Bond ◽  
Methylene Chloride ◽  
Ring Closure ◽  
Oxidative Carbonylation ◽  
Experimental Conditions ◽  
Carbonylation Reaction ◽  
Methanol Mixture

Oxidative carbonylation of 1,5-cyclooctadiene in methylene chloride-methanol mixture, catalyzed by Pd(II)-salts, gave rise to a bicyclic, bifunctional product under mild experimental conditions. The mechanism, involving multiple carbon monoxide and double bond insertions into the Pd(II)-carbon σ-bond, has been proposed, as being consistent with the outcome of this novel ring closure reaction.

Heterocyclic Syntheses Through Electrophilic Ring Closure Reactions of ortho-Allylaniline Systems

1991 ◽  
Vol 44 (12) ◽  
pp. 1749 ◽  
Author(s):  
KD Raner ◽  
AD Ward
Keyword(s):  
Double Bond ◽  
Hydrogen Chloride ◽  
Ring Closure ◽  
Subsequent Reaction ◽  
Amide Derivatives ◽  
Derivatives Of

Amide derivatives of 2-allylanilines have been prepared by metallation of the amide derivatives of the corresponding 2-bromoanilines and subsequent reaction with an allylic halide. The electrophile -promoted cyclization of these compounds has been investigated. The free allylanilines readily undergo aminomercuration to form unstable mercury derivatives of tetrahydroquinolines but the corresponding amide derivatives do not cyclize. Instead, oxymercuration of the double bond occurs. The allylanilines react with iodine to yield 3-iodo-1,2,3,4-tetrahydroquinolines. The anion of 2,2,2-trifluoro-N-[4-hydroxymethyl-2-(3-methylbut-2-enyl)phenyl] acetamide reacts with iodine to give a 2,3-dihydroindole. These iodinated compounds can be further cyclized with base to form 7,7a-dihydro-1H-azirino[1,2-a] indoles. One of these aziridine systems was cleaved with hydrogen chloride to form a mixture of chlorinated tetrahydroquinoline and dihydroindole analogous to the iodo systems.

Stereoelectronic effects in ring closure reactions: the 2′-hydroxychalcone – flavanone equilibrium, and related systems

1990 ◽  
Vol 68 (10) ◽  
pp. 1780-1785 ◽  
Author(s):  
Colin M. Brennan ◽  
Ian Hunt ◽  
Terence C. Jarvis ◽  
C. David Johnson ◽  
Peter D. McDonnell
Keyword(s):  
Double Bond ◽  
Michael Addition ◽  
Protonated Form ◽  
Ring Closure ◽  
Rate Limiting Step ◽  
Michael Adducts ◽  
Main Pathway ◽  
Rate Limiting ◽  
Bond Character ◽  
Influence Of Substituents

The 2′-hydroxychalcone (2-HOC6H4COCH=CHC6H4X)–flavanone equilibrium in trifluoroacetic acid (TFA) has been examined. The influence of substituents X on the rate of attainment of equilibrium shows that the 6-endo-trig mode of ring closure by Michael addition is disallowed, by demonstrating a negative ρ value for the reaction rate when X is varied. Reaction therefore proceeds either on the carbonyl-protonated form, which allows twisting about the 2,3 bond, its double bond character being reduced by resonance, or through direct rate-limiting protonation on the 2,3 double bond. Either pathway permits the allowed 6-exo-trig mode of ring closure to be followed. Alternative mechanisms involving intermolecular Michael addition of trifluoroacetate, followed by intramolecular 6-exo-tet displacement are considered. Such Michael adducts can be detected in the ring closures of 2-crotonyl-4-methylphenol and 4,4-dimethyl-1-(2-hydroxyphenyl)-2-penten-1-one in TFA, but they do not appear to lie on the main pathway, because the reactions proceed with equal facility in methanesulphonic acid/chloroform medium, which does not contain a suitable nucleophile for such a mechanism. Further important mechanistic information is given by studying the reactions in TFA-d, together with measurements on the (E)-2-methyl-3-oxo-5-arylpent-4-en-2-ol and 3′-methoxychalcone systems. These isotope effect studies, which yield kH/kD values of about 3, indicate that the proton is in flight during the rate-limiting step, and provide evidence against the mechanism involving a preequilibrium carbonyl protonation, such as in the Nazarov rearrangement of 3′-methoxychalcones, where kH/kD is ca. 0.7. Some results are also reported for ring closure of the 2-aminochalcones in TFA. Keywords: 2′-hydroxychalcones, flavanones, 3′methoxychalcones, 3-aryl-6-methoxyindanones, 2′-aminochalcones, 2-aryl-1, 2, 3, 4-tetrahydroquinolines, Baldwin's rules.

scholarly journals Oxidative and reductive cyclization in stiff dithienylethenes

2018 ◽  
Vol 14 ◽  
pp. 2812-2821 ◽  
Author(s):  
Michael Kleinwächter ◽  
Ellen Teichmann ◽  
Lutz Grubert ◽  
Martin Herder ◽  
Stefan Hecht
Keyword(s):  
Double Bond ◽  
Redox Potential ◽  
Electrochemical Behavior ◽  
Ring Closure ◽  
Reductive Cyclization ◽  
Ring Size ◽  
Major Pathway ◽  
Double Bond Isomerization ◽  
Almost All

The electrochemical behavior of stiff dithienylethenes, undergoing double bond isomerization in addition to ring-closure, has been investigated. Electrochromism was observed in almost all cases, with the major pathway being the oxidatively induced cyclization of the open isomers. The influence of the ring size (to lock the reactive antiparallel conformation) as well as substituents (to modulate the redox potential) on the electrocyclization was examined. In the series of derivatives with 6-membered rings, both the E- and the Z-isomer convert to the closed isomer, whereas for the 7-membered rings no cyclization from the E-isomer was observed. For both stiff and normal dithienylethenes bearing benzonitrile substituents an additional and rare reductive electrocyclization was observed. The mechanism underlying both observed electrocyclization pathways has been elucidated.

A Remarkably Facile Ring Closure Through Double Bond Participation

1962 ◽  
Vol 84 (18) ◽  
pp. 3517-3520 ◽  
Author(s):  
Werner. Herz ◽  
Gerald. Caple
Keyword(s):  
Double Bond ◽  
Ring Closure
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