Rate–equilibrium relationships based on the CH-acidity constants of oxocarbenium ions, for proton transfer from hydronium ion to α-methoxystyrenes: evidence for perfect synchronization between bond cleavage, bond formation, and positive-charge delocalization

1989 ◽  
pp. 167-171 ◽  
Author(s):  
Jean Toullec
Keyword(s):  
Proton Transfer ◽  
Positive Charge ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Acidity Constants ◽  
Charge Delocalization ◽  
Hydronium Ion ◽  
Oxocarbenium Ions ◽  
Equilibrium Relationships

scholarly journals Complete σ* intramolecular aromatic hydroxylation mechanism through O2 activation by a Schiff base macrocyclic dicopper(I) complex

2013 ◽  
Vol 9 ◽  
pp. 585-593 ◽  
Author(s):  
Albert Poater ◽  
Miquel Solà
Keyword(s):  
Schiff Base ◽  
Proton Transfer ◽  
Dft Calculations ◽  
Reaction Pathway ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Subsequent Reaction ◽  
O2 Activation ◽  
Aromatic Carbon ◽  
Aromatic Hydroxylation

In this work we analyze the whole molecular mechanism for intramolecular aromatic hydroxylation through O2 activation by a Schiff hexaazamacrocyclic dicopper(I) complex, [CuI 2(bsH2m)]2+. Assisted by DFT calculations, we unravel the reaction pathway for the overall intramolecular aromatic hydroxylation, i.e., from the initial O2 reaction with the dicopper(I) species to first form a CuICuII-superoxo species, the subsequent reaction with the second CuI center to form a μ-η2:η2-peroxo-CuII 2 intermediate, the concerted peroxide O–O bond cleavage and C–O bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII 2(bsH2m-O)(μ-OH)]2+.

scholarly journals Rate Dependence on Inductive and Resonance Effects for the Organocatalyzed Enantioselective Conjugate Addition of Alkenyl and Alkynyl Boronic Acids to β-Indolyl Enones and β-Pyrrolyl Enones

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1615
Author(s):  
Amy Boylan ◽  
Thien S. Nguyen ◽  
Brian J. Lundy ◽  
Jian-Yuan Li ◽  
Ravikrishna Vallakati ◽  
...  
Keyword(s):  
Positive Charge ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Reaction Rates ◽  
Boronic Acids ◽  
Key Factors ◽  
Resonance Contribution ◽  
Reaction Conditions ◽  
Resonance Effects ◽  
Resonance Stabilization

Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the enone β-carbon, the faster the reaction. For the latter, greater resonance stabilization of the benzylic cationic charge accelerates the reaction. Thus, reaction rates are increased by the closer proximity of inductive electron-withdrawing elements, but if resonance effects are involved, then increased rates are observed with electron-donating ability. Evidence for these trends in isomeric substrates is presented, and the application of these insights has allowed for reaction conditions that provide improved reactivity with previously problematic substrates.

Gas-phase proton-transfer reactions of the hydronium ion at 298 K

1979 ◽  
Vol 57 (12) ◽  
pp. 1518-1523 ◽  
Author(s):  
Gervase I. Mackay ◽  
Scott D. Tanner ◽  
Alan C. Hopkinson ◽  
Diethard K. Bohme
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Transfer Reactions ◽  
Flowing Afterglow ◽  
Hydronium Ion ◽  
Proton Transfer Reactions

Rate constants measured with the flowing afterglow technique at 298 ± 2 K are reported for the proton-transfer reactions of H3O+ with CH2O, CH3CHO, (CH3)2CO, HCOOH, CH3COOH, HCOOCH3, CH3OH, C2H5OH, (CH3)2O, and CH2CO. Dissociative proton-transfer was observed only with CH3COOH. The rate constants are compared with the predictions of various theories for ion–molecule collisions. The protonation is discussed in terms of the energetics and mechanisms of various modes of dissociation.

Organozinc-Mediated Direct C−C Bond Formation via C−N Bond Cleavage of Ammonium Salts

2017 ◽  
Vol 12 (19) ◽  
pp. 2554-2557 ◽  
Author(s):  
Dong-Yu Wang ◽  
Koki Morimoto ◽  
Ze-Kun Yang ◽  
Chao Wang ◽  
Masanobu Uchiyama
Keyword(s):  
Bond Cleavage ◽  
Bond Formation ◽  
Ammonium Salts

Double C–H Activation for the C–C bond Formation Reactions

2018 ◽  
Vol 15 (7) ◽  
pp. 882-903 ◽  
Author(s):  
Jialin Liu ◽  
Xiaoyu Xiong ◽  
Jie Chen ◽  
Yuntao Wang ◽  
Ranran Zhu ◽  
...  
Keyword(s):  
Molecular Design ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Hypervalent Iodine ◽  
Coupling Reactions ◽  
Bond Forming ◽  
Direct Functionalization ◽  
Catalyzed Reactions ◽  
Medium Ring ◽  
Bond Formation Reactions

Background: Among the numerous bond-forming patterns, C–C bond formation is one of the most useful tools for building molecules for the chemical industry as well as life sciences. Recently, one of the most challenging topics is the study of the direct coupling reactions via multiple C–H bond cleavage/activation processes. A number of excellent reviews on modern C–H direct functionalization have been reported by Bergman, Bercaw, Yu and others in recent years. Among the large number of available methodologies, Pdcatalyzed reactions and hypervalent iodine reagent mediated reactions represent the most popular metal and non-metal involved transformations. However, the comprehensive summary of the comparison of metal and non-metal mediated transformations is still not available. Objective: The review focuses on comparing these two types of reactions (Pd-catalyzed reactions and hypervalent iodine reagent mediated reactions) based on the ways of forming new C–C bonds, as well as the scope and limitations on the demonstration of their synthetic applications. Conclusion: Comparing the Pd-catalyzed strategies and hypervalent iodine reagent mediated methodologies for the direct C–C bond formation from activation of C-H bonds, we clearly noticed that both strategies are powerful tools for directly obtaining the corresponding pruducts. On one hand, the hypervalent iodine reagents mediated reactions are normally under mild conditions and give the molecular diversity without the presence of transition-metal, while the Pd-catalyzed approaches have a broader scope for the wide synthetic applications. On the other hand, unlike Pd-catalyzed C-C bond formation reactions, the study towards hypervalent iodine reagent mediated methodology mainly focused on the stoichiometric amount of hypervalent iodine reagent, while few catalytic reactions have been reported. Meanwhile, hypervalent iodine strategy has been proved to be more efficient in intramolecular medium-ring construction, while there are less successful examples on C(sp3)–C(sp3) bond formation. In summary, we have demonstrated a number of selected approaches for the formation of a new C–C bond under the utilization of Pd-catalyzed reaction conditions or hyperiodine reagents. The direct activations of sp2 or sp3 hybridized C–H bonds are believed to be important strategies for the future molecular design as well as useful chemical entity synthesis.

Oxidative C–S bond cleavage reaction of DMSO for C–N and C–C bond formation: new Mannich-type reaction for β-amino ketones

RSC Advances ◽  
2015 ◽  
Vol 5 (4) ◽  
pp. 3094-3097 ◽  
Author(s):  
Kai Sun ◽  
Yunhe Lv ◽  
Zhonghong Zhu ◽  
Liping Zhang ◽  
Hankui Wu ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Bond Formation ◽  
Cleavage Reaction ◽  
Type Reaction ◽  
Bond Cleavage Reaction

A novel oxidative C–S bond cleavage reaction of DMSO for N-methylation and subsequent C–C bond formation is described.

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