Spiropentylcarbinyl cation rearrangement. Stereochemistry of nucleophilic attack in a cyclopropylcarbinyl to cyclobutyl cation rearrangement and stereochemistry of the ring opening of the 1-cyclopropylcyclopropyl cation

1972 ◽  
Vol 94 (17) ◽  
pp. 6053-6059 ◽  
Author(s):  
Joseph J. Gajewski ◽  
John P. Oberdier
Keyword(s):  
Ring Opening ◽  
Nucleophilic Attack

Kinetics of the Imidazolium Ring-Opening of mRNA 5'-cap Analogs in Aqueous Alkali

2006 ◽  
Vol 71 (4) ◽  
pp. 567-578 ◽  
Author(s):  
Alicja Stachelska ◽  
Zbigniew J. Wieczorek ◽  
Janusz Stępiński ◽  
Marzena Jankowska-Anyszka ◽  
Harri Lönnberg ◽  
...  
Keyword(s):  
Electrostatic Interaction ◽  
Ring Opening ◽  
Nucleophilic Attack ◽  
Amino Groups ◽  
Hydroxide Ion ◽  
Methyl Group ◽  
Structural Modifications ◽  
Alkyl Groups ◽  
Imidazolium Ring ◽  
Kinetics Of

Second-order rate constants for the hydroxide-ion-catalyzed imidazolium ring-opening of several mono- and dinucleosidic analogs of mRNA 5'-cap have been determined. Intramolecular stacking of the two nucleobases in the dinucleosidic analogs, m7GpppN (m7G = 7-methylguanosine, N = 5'-linked nucleoside), and electrostatic interaction between the N-alkylated imidazolium ring and phosphate moiety have been shown to shield the m7G moiety against the nucleophilic attack of hydroxide ion. In addition, the effect of methylation of the nucleobase amino groups and replacement of the 7-methyl group with other alkyl groups have been studied. The influence of all the structural modifications studied turned out to be modest, the cleavage rates of the most and least reactive analogs (with the exception of non-phosphorylated nucleosides) differing only by a factor of 5.

Delineating the possibilities for intramolecular interception of the squarate ester cascade through the use of metalated enecarbamates

2000 ◽  
Vol 78 (6) ◽  
pp. 689-696 ◽  
Author(s):  
Jinsung Tae ◽  
Leo A Paquette
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Sequential Treatment ◽  
Nucleophilic Attack ◽  
Ring Strain ◽  
Multistep Process

Highly functionalized and annulated 2,4-cyclooctadienones are formed in a stereoselective manner by sequential treatment of squarate esters with a lithiated enecarbamate (six-membered ring or larger) and a cycloalkenyl- or 1-alkenyllithium reagent. The mechanistic details of this multistep process are presented. Particular attention is drawn to the step that involves intramolecular nucleophilic attack by a proximal oxido anion at the carbamate carbonyl and results in redirection of the cascade. This step is thwarted when five-membered cyclic enecarbamates are employed because of the excessive buildup of ring strain in the associated transition state.Key words: squarate esters, enecarbamates, conrotatory ring opening, intramolecular acylation, alkenyllithium reagents.

Construction of isoquinolinone framework from carboxylic ester directed umpolung ring opening of methylenecyclopropanes

2021 ◽  
Author(s):  
Min Shi ◽  
Hao-Zhao Wei ◽  
Yin Wei
Keyword(s):  
Ring Opening ◽  
Nucleophilic Attack ◽  
Reaction Pattern ◽  
Carboxylic Ester ◽  
Anionic Species

An unprecedented reaction pattern of functionalized methylenecyclopropanes (MCPs) has been disclosed in this paper, in which the nucleophilic attack of anionic species onto partially polarity-reversed MCP unit can be realized...

CARCINOGENICITY OF LACTONES: I. THE REACTION OF 4-METHYLBUTENO- AND 4-METHYLBUTANO-γ-LACTONES WITH PRIMARY AMINES

1966 ◽  
Vol 44 (9) ◽  
pp. 1059-1068 ◽  
Author(s):  
J. Bryan Jones ◽  
John M. Young
Keyword(s):  
Magnetic Resonance ◽  
Michael Addition ◽  
Ring Opening ◽  
Proton Magnetic Resonance ◽  
Mechanisms Of Action ◽  
Reaction Pathways ◽  
Nucleophilic Attack ◽  
Primary Amines ◽  
Acid Lactone ◽  
The Michael Addition

As the first stage in the investigations of the mechanisms of action of carcinogenic lactones, the reactions of 4-hydroxypent-2-enoic acid lactone (II, R = CH3), which is a carcinogen, and of the non-carcinogenic 4-hydroxypent-3-enoic (III, R = CH3) and 4-hydroxypentanoic (IV, R = CH3) acid lactones with methylamine and benzylamine have been studied. As expected, the carcinogenic lactone reacts to give the Michael addition products, whereas both inactive lactones undergo ring opening by nucleophilic attack at the carbonyl group. From the relative rates of reaction of the amines with the lactones it is concluded that the induction of tumors by II (R = CH3) does not involve alkylation of biological primary alkylamino groups. The proton magnetic resonance spectra of the products enable the different reaction pathways to be distinguished readily, and may provide the basis for rapid physicochemical screening of alkylation agents that are potential carcinogens.

The reactions of isothiazolium salts with selected nucleophilic reagents. The preparation of thieno[2,3-c]isothiazolium salts

1977 ◽  
Vol 55 (7) ◽  
pp. 1123-1128 ◽  
Author(s):  
David M. McKinnon ◽  
Mohammed E. R. Hassan ◽  
Mohinder Chauhan
Keyword(s):  
Ring Opening ◽  
Nucleophilic Attack ◽  
Isothiazolium Salts ◽  
Thiophene Derivatives ◽  
Nucleophilic Reagents

Isothiazolium salts react with a number of carbanions by attack on sulfur. Thiophene derivatives, formed by ring opening and recyclization, are often products but with cyclopentadiene, pseudoazulene products are obtained. 3-Amino-2-acylthiophenes, prepared by suitable nucleophilic attack, are synthetic precursors of thieno[2,3-c]isothiazolium salts

scholarly journals Solvent-Free Ring Cleavage Hydrazinolysis of Certain Biginelli Pyrimidines

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Mohamed A. Said ◽  
Wagdy M. Eldehna ◽  
Hazem A. Ghabbour ◽  
Maha M. Kabil ◽  
Nasser S. Al-shakliah ◽  
...  
Keyword(s):  
Hydrazine Hydrate ◽  
Ring Opening ◽  
Solvent Free ◽  
Nucleophilic Attack ◽  
Ring Cleavage ◽  
Amino Group ◽  
Free Ring ◽  
Terminal Amino ◽  
Solvent Free Reaction

Certain Biginelli pyrimidines with ester substitution in C5 were subjected to unexpected ring opening upon solvent-free reaction with hydrazine hydrate to give three products: pyrazole, arylidenehydrazines, and urea/thiourea, respectively. The nonisolable carbohydrazide intermediates are formed firstly followed by the intermolecular nucleophilic attack of terminal amino group of hydrazide function on sp2 C6 rather than the sp3 C4 to give the ring adduct which was produced as a final product.

Synthese und Aggregatbildung eines 5-Hydroxy-2,5-dihydropyrrols. Enantiomerenreine, eindimensionale Stränge durch Wasserstoffbrückenbindungen und chiroselektive Selbstorganisation/Synthesis and Aggregation of a 5-H ydroxy-2,5-dihydropyrrole. Enantiomerically Pure, One-dimensional Strands via Hydrogen Bonds and Chiroselective Self Organization

1999 ◽  
Vol 54 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Rolf W. Saalfrank ◽  
Jochen Nachtrab ◽  
Stephan Reck
Keyword(s):  
Hydrogen Bonds ◽  
Ring Opening ◽  
Self Organization ◽  
Nucleophilic Attack ◽  
X Ray Diffraction ◽  
Enantiomerically Pure ◽  
One Dimensional ◽  
X Ray ◽  
Self Selection ◽  
The One

Reaction of dimethyl 1,3-acetonedicarboxylate 8 with oxalylchloride 2 and magnesium chloride as catalyst yielded 2,3-dioxo-2,3-dihydrofuran 9, which is in equilibrium with tautomer 10 (9:10 = 1:2). Addition of thionyl chloride to a mixture of 9/10 afforded 3-chloro-2(5H)-furanone 11. The structure of 11 was unequivocally established by X-ray diffraction, which indirectly proved the structure of 10 as well. Ring opening of 11 by nucleophilic attack with benzylamine 14 in C2-position and subsequent recyclization led to racemic 3-chloro-5-hydroxy-2-oxo-2,5-dihydropyrrole 15. According to a single crystal X-ray analysis, 15 aggregates via stereospecific self selection through hydrogen bonds to give chiroselectively the one-dimensional strands ∞1[(S)-15] and ∞1[( R)-15]

Synthetically Important Ring-Opening Acylations of Alkoxybenzenes

Synthesis ◽  
2020 ◽  
Vol 52 (24) ◽  
pp. 3764-3780
Author(s):  
Ranadeep Talukdar
Keyword(s):  
Lewis Acid ◽  
Ring Opening ◽  
Building Blocks ◽  
Nucleophilic Attack ◽  
Cyclic Ketones ◽  
Wide Range ◽  
Cyclic Molecules ◽  
Nucleophilic Ring Opening ◽  
Molecular Rings

AbstractCyclic ketones, anhydrides, lactams and lactones are a particular class of molecules that are often used in synthesis, wherein their electrophilic properties are leveraged to enable facile Friedel–Crafts ring openings through nucleophilic attack at the carbonyl sp2 centre. The use of electron-rich alkoxybenzenes as nucleophiles has also become important since the discovery of the Friedel–Crafts reaction. As a result, various isomeric alkoxybenzenes are used for preparing starting materials in target-oriented syntheses. This review covers the instances of different alkoxybenzenes that are used as nucleophiles in ring-opening acylations with carbonyl-containing cyclic electrophiles, for the construction of important building blocks for multistep transformations. This review summarizes the ring-opening functionalization of three- to seven-membered molecular rings with alkoxybenzenes in a Friedel–Crafts fashion. Sometimes the rings need subtle or considerable activation by the help of Lewis acid(s), followed by nucleophilic attack. This review is aimed to be a summary of the important acylations of electron-rich alkoxybenzenes by nucleophilic ring-opening of cyclic molecules. The works cited employ a wide range of conditions and differently substituted substrates for target-oriented syntheses.1 Introduction and Scope2 Arenes for Acylative Ring Opening2.1 Three-Membered Rings: Ring Opening of Oxirane-2,3-dione2.2 Four-Membered Rings2.2.1 Ring Opening of Cyclobutanones2.2.2 Ring Opening of β-Lactams2.2.3 Ring Opening of β-Lactone2.3 Five-Membered Rings2.3.1 Ring Opening of Phthalimides2.3.2 Ring Opening of γ-Lactones2.3.3 Ring Opening of Anhydrides2.4 Six-Membered Rings2.5 Seven-Membered Rings3 Conclusion

scholarly journals Photocatalytic Ring Opening of α-Epoxyketones in Cyclopentanone

2011 ◽  
Vol 66 (6) ◽  
pp. 603-610
Author(s):  
Hamaid R. Memarian ◽  
Gholrokh Shokuhimehr ◽  
Mousa Soleymani
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Ring Opening ◽  
Bond Cleavage ◽  
Nucleophilic Attack

Electron transfer-induced ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate (TPT) in cyclopentanone resulted in the diastereoselective formation of 2,5-dioxaspiro[4,4]- nonanes through Cα-O bond cleavage and following nucleophilic attack of cyclopentanone to radical cation intermediates. The readiness for ring opening is influenced by the nature and the location of the additional s`ubstituent on the α-epoxyketones.

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