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.

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.

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.

Effect of Substituents and Solvents on Phenol-Isocyanate Urethane Reaction

2010 ◽  
Vol 150-151 ◽  
pp. 23-26 ◽  
Author(s):  
Peng Fei Yang ◽  
Yong De Han ◽  
Tian Duo Li
Keyword(s):  
Hydrogen Atom ◽  
Nitrogen Atom ◽  
Rate Constants ◽  
Nucleophilic Addition ◽  
Reaction Rate ◽  
Effect Of Substituents ◽  
Reaction Rate Constants ◽  
Ft Ir ◽  
Polarity Of Solvents

In this study, the urethane reaction of several phenols with isocyanate was monitored with in-situ FT-IR. Reaction rate constants were calculated out to investigate the effect of substituents in phenols, as well as the polarity of different solvents. It showed that the polarity of solvents largely affected the reaction rate even without catalyst. The reactivity increased in the following order: Xylene < 1,4-Dioxane < Cyclohexanone. Furthermore, an electron-withdrawing substituent in phenols increased the reactivity of hydroxyl with isocyanate. The reason may be that the H-O bond in phenols could be easily polarized under the influence of electron-withdrawing substituent, where the hydrogen atom was more likely to attack the nitrogen atom of -NCO, thus the nucleophilic addition happened easier.

Theoretical study of regioselectivity in nucleophilic addition to unsymmetrical cyclic anhydrides. Intrinsic reactivity and influence of the cation

1981 ◽  
Vol 59 (16) ◽  
pp. 2457-2462 ◽  
Author(s):  
Margaret M. Kayser ◽  
Odile Eisenstein
Keyword(s):  
Carbonyl Group ◽  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
Dominant Factor ◽  
Molecular Orbital Calculations ◽  
Optimum Position ◽  
Cyclic Anhydrides ◽  
Intrinsic Reactivity ◽  
Reaction Media ◽  
Phthalic Anhydrides

Ab initio molecular orbital calculations have been carried out for the series of succinic, maleic, and phthalic anhydrides unsymmetrically substituted with CH3, CH3O, Cl, F, and CN. The size of the LUMO coefficient on the carbon atom of the carbonyl group provides a reliable guide to the relative reactivities of the two carbonyl functions. The predictions based on the intrinsic reactivities are in good agreement with the regioselectivities observed in metal hydride reductions of succinic anhydrides. In the series of maleic and phthalic anhydrides the above considerations are applicable only to methyl derivatives. The compounds substituted with lone pairs-bearing groups (OCH3, Cl, F) form stable chelates with the cations present in the reaction media. Since the chelated carbonyl group is strongly activated toward the nucleophilic addition, the "bridging" effect is the dominant factor controlling orientation of hydride addition. The optimum position for the nucleophilic attack in cyclic anhydrides was calculated. The results confirm the generality of the nonperpendicular, restricted path of nucleophilic attack on the carbonyl group in succinic anhydride.

Formation of an Unusual Bis(diguanidinate) Ligand via Nucleophilic Attack of a Guanidinate onto a Carbodiimide

2014 ◽  
Vol 67 (7) ◽  
pp. 1030 ◽  
Author(s):  
Rebecca L. Melen ◽  
Hayley R. Simmonds ◽  
Hubert Wadepohl ◽  
Paul T. Wood ◽  
Lutz H. Gade ◽  
...  
Keyword(s):  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
In Situ Reactions

During an investigation of the synthesis of the new mono- and bis(guanidinate) complexes [{iPr2NC(···NiPr)2}GaCl2] (2) and [{iPr2NC(···NiPr)2}2GaCl] (3) from the in situ reactions of the lithium guanidinate [{iPr2NC(···NiPr)2}Li]n (1) with GaCl3, an unexpected new guanidinate expansion reaction was uncovered in which it is found that the nucleophilic addition of 2 to the carbodiimide, iPrN=C=NiPr, gives [iPrN{C(NiPr)=NiPr}{C(=NiPr)NiPr2}GaCl2] (4), containing an unusual bis(diguanidinate) ligand.

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