Phosphato complexes of cobalt(III). II. Reversible chelation and ring-opening reactions

1968 ◽  
Vol 21 (1) ◽  
pp. 57 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Rate Constants ◽  
Ring Opening ◽  
Base Catalysis ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Protonated Forms ◽  
Acid And Base ◽  
Chelation Reaction ◽  
Ph Range ◽  
Monodentate Complex

The bidentate phosphato complex Co en2PO40; has been shown to exist in rapid reversible equilibrium with the monodentate complex Co en2OH.HPO40 A detailed kinetic analysis of the opposed ring-opening and ring-closing (or chelation) reactions has evaluated rate constants for each of the protonated forms in acid and basic media. The ring-opening reaction is subject to both acid and base catalysis. However, within the pH range 6-9, the bidentate form containing a four-member phosphate ring is thermodynamically more stable than the monodentate form. This is ascribed to a rapid chelation reaction arising from a favourable cis hydrogen-bonded transition state.

scholarly journals Torquoselectivity of the Ring-Opening Reaction of 3,3-Dihalosubstituted Cyclobutenes: Lone Pair Repulsion and Cyclic Orbital Interaction

2019 ◽  
Author(s):  
Yuji Naruse ◽  
Atsushi Takamori
Keyword(s):  
Double Bond ◽  
Ring Opening ◽  
Lone Pair ◽  
Repulsive Interaction ◽  
Orbital Interaction ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Major Factors ◽  
Vacant Orbital ◽  
Model Reactions

<div><div>Three major factors determine torquoselectivity, which is the diastereoselectivity in electrocyclic ring-opening reactions to produce <i>E</i>/<i>Z</i>-double bond(s). One is the interaction between the decomposing s<sub>CC</sub> bond and low-lying vacant orbital(s), such as a p*- or s*-orbital on the substituent, which promotes the reaction, resulting in inward rotation of the substituent. Second, for a substituent with a lone pair(s), repulsive interaction between the decomposing s-bond and the lone pair(s) hinders inward rotation, so that the products of outward rotation should be preferred. Finally, a more strongly donating s-electron-donating group (sEDG) rotates inwardly due to stabilization by phase-continuous cyclic orbital interaction. We compared the latter two interactions, repulsion between the lone pairs on the substituent and stabilization from phase-continuous cyclic orbital interaction, to determine which has a greater effect on the diastereoselectivity. We considered a series of model reactions with halogen substituents, and concluded that the diastereoselectivity is mainly controlled by cyclic orbital interaction.<br></div></div>

scholarly journals Asymmetric ring-opening reaction of meso-epoxides with aromatic amines using homochiral metal–organic frameworks as recyclable heterogeneous catalysts

RSC Advances ◽  
2018 ◽  
Vol 8 (49) ◽  
pp. 28139-28146 ◽  
Author(s):  
Koichi Tanaka ◽  
Maya Kinoshita ◽  
Jun Kayahara ◽  
Yutaro Uebayashi ◽  
Kazusada Nakaji ◽  
...  
Keyword(s):  
Aromatic Amines ◽  
Ring Opening ◽  
Heterogeneous Catalysts ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Amino Alcohols ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Metal Organic ◽  
Asymmetric Ring Opening

Asymmetric ring-opening reactions of meso-epoxides by aromatic amines were achieved by using some chiral metal–organic frameworks. The corresponding β-amino alcohols were obtained with good yields and enantioselectivities (up to 97% ee).

Thiophene Ring-Opening Reactions III: One-Pot Synthesis and Antitumor Activity of 1,3,4-Thiadiazoline–Benzothiazolo[3,2-b]pyridazine Hybrids

2021 ◽  
Vol 18 ◽  
Author(s):  
Ahmad Ahmad Abdullah ◽  
Jalal Zahra ◽  
Salim Sabri ◽  
Firas Awwadi ◽  
Mohammed Abadleh ◽  
...  
Keyword(s):  
Ring Opening ◽  
Thiophene Ring ◽  
Direct Interaction ◽  
X Ray Diffraction ◽  
One Pot ◽  
One Pot Synthesis ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Intramolecular Cyclizations ◽  
The One

Introduction: The preparation of model 6-chloro-5-nitrothieno[2,3-c]pyridazines incorporating (2'-halo-5'-nitrophenyl) entity is described. Interaction of these substrates with N'-(aryl)benzothiohydrazides, in the presence of triethylamine, followed a formal [4+1] annulation, furnishing the respective 1,3,4-thiadiazoline–benzothiazolo [3,2-b]pyridazine hybrids directly. This one-pot synthesis implies thiophene ring-opening and two consecutive intramolecular cyclizations. The structures of the synthesized new hybrids are supported by MS, NMR, and IR spectral data and further confirmed by single-crystal X-ray diffraction. These hybrids exhibit antiproliferative activity with notable selectivity against solid tumor cell lines (IC50: 4-18 μM). Aims: This study aimed at exploring the scope and applicability of thiophene ring-opening reaction towards the synthesis of new thiadiazoline–[fused]tricyclic conjugates. Background: α-Chloro-β-nitrothienopyridazine underwent ring-opening upon reacting with N'-(aryl)benzothiohydrazides generating 1,3,4-thiadiazoline–benzothiazolo[3,2-b]pyridazines. Objective: This new thiophene ring-opening reaction is applied to the one-pot synthesis of thiadiazoline–benzothiazolo[3,2-b]pyridazine couples. Method: A direct interaction of α-chloro-β-nitrothienopyridazine with N'-(aryl)benzothiohydrazide at room temperature for 1-2 h occurred. Result: α-Chloro-β-nitrothieno[2,3-c]pyridazines are suitable substrates for the facile synthesis of thiadiazoline–benzothiazolo[3,2-b]pyridazine hybrids. Conclusion: This novel ring-opening reaction proceeds via formal [4+1] annulation and provides a versatile approach to various conjugated and/or fused five-membered heterocycles.

Palladium-Catalyzed Synthesis of Polysubstituted Pyrazoles by Ring-Opening Reactions of 2H-Azirines with Hydrazones

Synlett ◽  
2020 ◽  
Author(s):  
Jiaan Shao ◽  
Ke Shu ◽  
Wenteng Chen ◽  
Shuangrong Liu ◽  
Huajian Zhu ◽  
...  
Keyword(s):  
Ring Opening ◽  
Chemical Conversion ◽  
Alternative Route ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Palladium Catalyzed ◽  
Plausible Mechanism

AbstractA palladium–catalyzed ring-opening reaction of 2H-azirines with hydrazones has been developed. This protocol provides an alternative route for the construction of various polysubstituted pyrazoles with a wide substrate scope. Moreover, a plausible mechanism is proposed for this reaction, which should further enrich the chemical conversion of 2H-azirines.

Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

1984 ◽  
Vol 62 (6) ◽  
pp. 1120-1123 ◽  
Author(s):  
John D. Reinheimer ◽  
Nicolas Sourbatis ◽  
Robert L. Lavallee ◽  
Douglas Goodwin ◽  
George L. Gould
Keyword(s):  
Ring Opening ◽  
Pyridine Ring ◽  
Ring Closure ◽  
Polar Solvents ◽  
Open Chain ◽  
Decomposition Products ◽  
Aqueous Sodium ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Kinetics Of

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

Remarkable improvement of epoxide ring-opening reaction efficiency and selectivity with water as a green regulator

2021 ◽  
Author(s):  
Zifei Yan ◽  
Chencan Du ◽  
Guangsheng Luo ◽  
Jian Deng
Keyword(s):  
Ring Opening ◽  
Epoxide Ring ◽  
Efficient Production ◽  
Epoxide Ring Opening ◽  
Reaction Efficiency ◽  
Remarkable Improvement ◽  
Glycidyl Esters ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions

Glycidyl esters are synthesized through the epoxide ring-opening reactions, and the reaction efficiency must be greatly improved for green and efficient production. In this work, the structure of the side...

ChemInform Abstract: Acid- and Base-Catalyzed Ring-Opening Reactions of a Sterically Hindered Epoxide.

ChemInform ◽  
1987 ◽  
Vol 18 (41) ◽  
Author(s):  
H. MAYR ◽  
R. KOSCHINSKY ◽  
E. WILL ◽  
E. BAEUML
Keyword(s):  
Ring Opening ◽  
Ring Opening Reactions ◽  
Acid And Base ◽  
Sterically Hindered

Ringöffnungsreaktionen an bioreaktiven Lactamsystemen / Ring Opening Reactions of Bioreactive Lactam Systems

1987 ◽  
Vol 42 (5) ◽  
pp. 603-612 ◽  
Author(s):  
Hermann Frister ◽  
Eckhard Schlimme
Keyword(s):  
Amino Acid ◽  
Ring Opening ◽  
Side Chains ◽  
Amino Groups ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Amino Acid Side Chains ◽  
Tin Tetrachloride ◽  
Model Reactions

Abstract 1-β-ᴅ-Ribofuranosylpyrrolidin-2,5-dione (9) was synthesized by ribosylation of N-silylated succinimide (7) with 1,2,3,5-tetra-O-acetyl-β-ᴅ-ribofuranose in acetonitril in the presence of tin tetrachloride. The compounds 9, 1-β-ᴅ-ribofuranosyl-l-H-pyrrol-2,5-dione (5) and N-methyl- maleinimide (2) were converted with ammonia to the ring-opened components 16. 14 and 15. The bioreactivity of the N-maleinimide derivatives 2 and 5 with respect to addition and ring-opening reactions with amino acid side chains containing either thiol or amino groups was shown in model reactions with glutathion (compds. 17,18) and lysine (compds. 19, 20). The ring opening reaction of 3-methyl-3-phenyl-1-β-ᴅ-ribofuranosylpyrrolidin-2,5-dione (11) with lysine yields 21, thus demonstrating the possibility of glycosuccinylation of amino groups in proteins.

scholarly journals Preparation and ring-opening reactions of N-diphenylphosphinyl vinyl aziridines

2013 ◽  
Vol 9 ◽  
pp. 852-859 ◽  
Author(s):  
Ashley N Jarvis ◽  
Andrew B McLaren ◽  
Helen M I Osborn ◽  
Joseph Sweeney
Keyword(s):  
Good Yield ◽  
Ring Opening ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Diphenylphosphinyl Imines

Predominantly (E)-N-diphenylphosphinyl vinyl aziridines are prepared by a reaction of N-diphenylphosphinyl imines with α-bromoallyllithium in the presence of freshly fused ZnCl2. These aziridines undergo a ring-opening reaction with a variety of carbon and heteronucleophiles, in good yield, and generally with good regioselectivity.

scholarly journals Ring-opening reaction of 2,5-dioctyldithieno[2,3-b:3',2'-d]thiophene in the presence of aryllithium reagents

2013 ◽  
Vol 9 ◽  
pp. 767-774 ◽  
Author(s):  
Hao Zhong ◽  
Jianwu Shi ◽  
Jianxun Kang ◽  
Shaomin Wang ◽  
Xinming Liu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ring Opening ◽  
H Nmr ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
C Nmr

In this paper, the ring-opening reaction of 2,5-dioctyldithieno[2,3-b:3',2'-d]thiophene with aryllithium in THF at low temperature to generate 2'-arylthio-3,3'-bithiophene-2-carbaldehydes is studied. Nine examples are explored and all the products are characterized by 1H NMR, 13C NMR and HRMS. The relative relationship between the structures of aryl groups and the efficiency of ring-opening reactions are discussed.

Sign in / Sign up

Export Citation Format

Share Document