SNH methodology and new approaches to condensed heterocyclic systems

2004 ◽  
Vol 76 (9) ◽  
pp. 1621-1631 ◽  
Author(s):  
V. N. Charushin ◽  
O. N. Chupakhin
Keyword(s):  
Aromatic Ring ◽  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
New Approaches ◽  
Snh Methodology ◽  
Key Steps

The review surveys the reactions of electron-deficient azaaromatic compounds with mono- and bifunctional nucleophilies in which a nucleophilic attack at the unsubstituted CH carbon of an aromatic ring is one of the key steps. Use of the SNH methodology for the synthesis of fused heterocyclic systems by means of nucleophilic addition –addition AN–AN, addition –substitution of hydrogen AN–SNH, tandem substitution of hydrogen SNH–SNH, and other strategies will be discussed. Intramolecular SNH reactions will also be considered as effective synthetic tools to obtain condensed heterocyclic systems.

Sterically hindering the trajectory of nucleophilic attack towards p-benzynes by a properly oriented hydrogen atom: An approach to achieve regioselectivity

2021 ◽  
Author(s):  
Monisha Singha ◽  
Prabuddha Bhattacharya ◽  
Debashis Ray ◽  
Amit Basak
Keyword(s):  
Hydrogen Atom ◽  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
Bergman Cyclization ◽  
Keen Interest

Nucleophilic addition to p-benzynes, derived via Bergman Cyclization has become a topic of keen interest. Studying the regioselectivity in such addition can reveal important information regarding the parameters controlling such...

Reactions of bridging C3 ligands in diiron complexes: Unconventional routes to new functionalized organic frames

2010 ◽  
Vol 82 (7) ◽  
pp. 1555-1568 ◽  
Author(s):  
Valerio Zanotti
Keyword(s):  
Functional Groups ◽  
Nucleophilic Addition ◽  
Metal Center ◽  
Unusual Reaction ◽  
Nucleophilic Attack ◽  
Double Bonds ◽  
Bridging Ligands ◽  
Reaction Patterns

Diiron complexes containing C3 ligands, such as vinyliminium and vinylalkylidene bridging units, display unusual reaction patterns, not observed when the same organic fragments are bound to a single metal center, or not coordinated. Bridging vinyliminium complexes [Fe2{μ-η1:η3-C(NMe2)CH=CR}(μ-CO)(CO)(Cp)2][SO3CF3] undergo nucleophilic addition at the iminium C or at α-C position, which is uncommon since non-coordinated vinyliminium species generally undergo conjugated (Michael type) nucleophilic attack. Likewise, bridging vinyliminium ligands undergo new and unusual transformations consisting of the deprotonation and replacement of the α-CH by a variety of functional groups. These reactions, resulting in the formation of C–C and C–heteroatom single and double bonds, produce new bridging ligands of the type [μ-C(NMe2)C(X)CR) (X = S, O, Se, SPh, CNMe, NNCHCO2Me]. Removal of the vinylalkylidene ligands from the bridging coordination is achieved by a [3 + 2] cycloaddition with alkynes. The reaction leads to the formation of ferrocenes containing one polysubstituted Cp ring, which results from the cycloaddition of the bridging C3 ligand with alkynes. This result suggests a new possible route for the synthesis of polyfunctionalized ferrocenes.

Nucleophilic Displacement in Polyhalogenoaromatic Compounds. XIII. Polyfluoroarene Systems

1987 ◽  
Vol 40 (2) ◽  
pp. 241 ◽  
Author(s):  
RK Atwal ◽  
R Bolton
Keyword(s):  
Benzene Ring ◽  
Aromatic Ring ◽  
Rate Coefficients ◽  
Nucleophilic Attack ◽  
Single Entity ◽  
Perfect Correlation ◽  
Nucleophilic Displacement ◽  
Aromatic Systems

Rate coefficients are reported for the methoxydefluorination of decafluoro-biphenyl and -phen-anthrene, of octafluoro-biphenylene, -naphthalene, -acenaphthylene, and -toluene, of 4H- heptafluorotoluene and the 4-bromo and 4-phenyl analogues, and of tetradecafluoro-4,4'- dimethylbiphenyl in methanol at 298 K. These rates are compared with theoretically calculated reactivities; none give perfect correlation. The orientation of nucleophilic attack upon polyfluorinated aromatic systems may be simply understood by considering each aromatic ring to act as a single entity and neglecting the effects of the carbon substituents, so that the orientation of attack of each benzene ring is the same as that of the corresponding polyfluorobenzene.

Correlation analysis of reactivity in the addition of substituted benzylamines to β-nitrostyrene

1996 ◽  
Vol 74 (4) ◽  
pp. 625-629 ◽  
Author(s):  
Neeta Jalani ◽  
Seema Kothari ◽  
Kalyan K. Banerji
Keyword(s):  
Activation Energy ◽  
Correlation Analysis ◽  
Rate Constant ◽  
Steric Hindrance ◽  
Nucleophilic Addition ◽  
Regression Coefficients ◽  
Nucleophilic Attack ◽  
Arrhenius Activation Energy ◽  
First Order ◽  
Kinetics Of

The kinetics of addition of a number of ortho-, meta-, and para-substituted benzylamines to β-nitrostyrene (NS) in acetonitrile have been studied. The reaction is first order with respect to NS. The order with respect to the amine is higher than one. It has been shown that the reaction follows two mechanistic pathways, uncatalyzed and catalyzed by the amine. The Arrhenius activation energy for the catalyzed path is negative, indicating the presence of a pre-equilibrium (k1, k−1) leading to the formation of a zwitterion. The values of the rate constant, k1, for the nucleophilic attack have been determined for 28 benzylamines. The rate constant k1 was subjected to correlation analysis using Charton's LDR and LDRS equations. The polar regression coefficients are negative, indicating the formation of a cationic species in the transition state. The reaction is subject to steric hindrance by ortho substituents. Key words: nucleophilic addition, benzylamines, correlation analysis, kinetics, alkene.

scholarly journals Bioinspired total synthesis of tetrahydrofuran lignans by tandem nucleophilic addition/redox isomerization/oxidative coupling and cycloetherification reactions as key steps

2018 ◽  
Vol 16 (5) ◽  
pp. 750-755 ◽  
Author(s):  
Pratap R. Jagtap ◽  
Ivana Císařová ◽  
Ullrich Jahn
Keyword(s):  
Total Synthesis ◽  
Oxidative Coupling ◽  
Nucleophilic Addition ◽  
Key Steps ◽  
Redox Isomerization

Three steps suffice to complete a bioinspired total synthesis of tetrahydrofuran lignans using tandem addition/isomerization/dimerization and cycloetherification reactions.

A Study of Reactivity of Model Compounds of Lignin Biopolymer

2021 ◽  
Vol 316 ◽  
pp. 75-80
Author(s):  
Oleg Kh. Karimov ◽  
Galina Yu. Kolchina ◽  
Eldar M. Movsumzade
Keyword(s):  
Aromatic Ring ◽  
Quantum Chemical ◽  
Density Functional ◽  
Nucleophilic Attack ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Hartree Fock ◽  
Quantitative Characteristics ◽  
Derivatives Of ◽  
Hybrid Density Functional

In the framework of method of the B3LYP hybrid density functional and the restricted Hartree-Fock method, quantum-chemical calculations of model compounds of lignin, i.e. derivatives of p-hydroxycinnamic alcohol were carried out. The structures and reactivity of coumaric, coniferyl and synapol alcohols were studied. Quantitative characteristics of the reactivity of these acids are given. It is found that the electronic structure of lignin is determined primarily by the charge distribution in its structural phenylpropane unit. In the molecules of all model compounds of lignin, the center for nucleophilic attack is the carbon of aromatic ring (E-ring) with a hydroxyl group, and in the molecule of synapol alcohol, this center is also the carbon of the aromatic ring (E-ring) with a methoxy group. In all three compounds, a center with an increased electron density appears on the Сβ carbon atom.

Microwave-assisted periselective annulation of triarylphosphenes with aldehydes and ketones

2020 ◽  
Vol 18 (46) ◽  
pp. 9526-9537
Author(s):  
Yun Luo ◽  
Zhicheng Fu ◽  
Xingyang Fu ◽  
Changle Du ◽  
Jiaxi Xu
Keyword(s):  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
Microwave Assisted ◽  
Aldehydes And Ketones

Microwave-assisted and improved periselective synthesis of benzo-δ-phosphinolactones through the nucleophilic attack of in situ generated triarylphosphenes with aldehydes and ketones followed by intramolecular nucleophilic addition.

Detection and kinetic characterization of SNV intermediates. Reactions of thiomethoxybenzylidene Meldrum's acid with thiolate ions, alkoxide ions, OH-, and water in aqueous DMSO

1999 ◽  
Vol 77 (5-6) ◽  
pp. 584-594 ◽  
Author(s):  
Claude F Bernasconi ◽  
Rodney J Ketner ◽  
Xin Chen ◽  
Zvi Rappoport
Keyword(s):  
Rate Constants ◽  
Nucleophilic Addition ◽  
Equilibrium Constants ◽  
Intrinsic Rate ◽  
Nucleophilic Attack ◽  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Nucleophilic Vinylic Substitution ◽  
Steady State Levels ◽  
Vinylic Substitution

The reaction of thiomethoxybenzylidene Meldrum's acid (5-SMe) with thiolate and alkoxide ion nucleophiles is shown to proceed by the two-step addition-elimination SNV mechanism in which the tetrahedral intermediate accumulates to detectable levels. For the reactions with thiolate ions, rate constants for nucleophilic addition (k1RX), its reverse (k-1RX), and for conversion of the intermediate to products (k2RX) were determined. For the reactions with alkoxide ions, only k1RX and k-1RX could be obtained; the intermediate in these reactions did not yield the expected substitution products, and hence no k2RX values could be determined. The reactions with OH- and water are believed to follow the same mechanism, but the respective intermediates remain at steady-state levels, and only k1OH and k1H²O for nucleophilic attack on 5-SMe were measurable. New insights regarding structure-reactivity behavior in SNV reactions are gained from comparisons of rate and equilibrium constants in the reactions of 5-SMe with the corresponding parameters in the reactions of methoxybenzylidene Meldrum's acid (5-OMe) and benzylidene Meldrum's acid (5-H). In particular, the relative importance of steric and pi-donor effects of the MeS vs. MeO group in 5-SMe and 5-OMe, respectively, and their role in affecting the intrinsic rate constants for nucleophilic addition, has been clarified by these comparisons. Our results also add support to a previous suggestion that soft-soft type interactions tend to increase intrinsic rate constants for thiolate ion addition to vinylic substrates, especially 5-SMe with the soft MeS group.Key words: nucleophilic vinylic substitution, intrinsic rate constants, transition state imbalances, steric/pi-donor/anomeric effects.

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