scholarly journals Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

2011 ◽  
Vol 7 ◽  
pp. 744-758 ◽  
Author(s):  
Vadim A Soloshonok ◽  
Donna J Nelson
Keyword(s):  
Double Bond ◽  
Theoretical Data ◽  
Comprehensive Analysis ◽  
Asymmetric Induction ◽  
Steric Effects ◽  
Addition Reactions ◽  
Electronic Effects ◽  
Broad Perspective ◽  
Factors Influencing ◽  
Electronic And Steric Effects

A broad perspective of various factors influencing alkene selenenylation has been developed by concurrent detailed analysis of key experimental and theoretical data, such as asymmetric induction, stereochemistry, relative reactivities, and comparison with that of alkene sulfenylation. Alkyl group branching α to the double bond was shown to have the greatest effect on alkene reactivity and the stereochemical outcome of corresponding addition reactions. This is in sharp contrast with other additions to alkenes, which depend more on the degree of substitution on C=C or upon substituent electronic effects. Electronic and steric effects influencing asymmetric induction, stereochemistry, regiochemistry, and relative reactivities in the addition of PhSeOTf to alkenes are compared and contrasted with those of PhSCl.

Ring-opening copolymerization of epoxide and dianhydride in the presence of manganese(III) asymmetrical bis-Schiff base catalysts

2014 ◽  
Vol 92 (11) ◽  
pp. 1098-1105 ◽  
Author(s):  
Deng-Feng Liu ◽  
Lu-Qun Zhu ◽  
Jing Wu ◽  
Li-Ying Wu ◽  
Xing-Qiang Lü
Keyword(s):  
Schiff Base ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Structure Design ◽  
Steric Effects ◽  
Chain Growth ◽  
Electronic Effects ◽  
Reaction Conditions ◽  
Base Catalysts ◽  
Electronic And Steric Effects

Based on a series of asymmetrical bis-Schiff base H2Ln (n = 1–4) ligands with different electronic and steric effects, a series of [Mn(Ln)Cl] complexes 1–4 are obtained and shown to be effective catalysts in ring-opening copolymerization of epoxides and dianhydrides. Through the structure design, the input of electron-withdrawing bromine substituent para to the phenoxide group of the complexes is considerately beneficial to the improved activities. Moreover, steric and electronic effects of the suitable MeO substituent at the ortho orientation on the phenoxide group may both play a role in the formation of alternating ring-opening copolymers under the identical reaction conditions. In three cocatalysts tested, n-Bu4NBr is positive to monomer conversion and chain growth of polymer.

Electronic and steric effects of various silyl groups in radical addition reactions

1998 ◽  
Vol 39 (22) ◽  
pp. 3721-3724 ◽  
Author(s):  
Jih Ru Hwu ◽  
Ke Yung King ◽  
I-Fay Wu ◽  
Gholam H. Hakimelahi
Keyword(s):  
Radical Addition ◽  
Steric Effects ◽  
Addition Reactions ◽  
Silyl Groups ◽  
Electronic And Steric Effects

Structures and photochemistry of 1,5-disubstituted dibenzobarrelenes

1996 ◽  
Vol 52 (1) ◽  
pp. 151-158
Author(s):  
R. Jones ◽  
S. J. Rettig ◽  
J. R. Scheffer ◽  
J. Trotter ◽  
J. Yang
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
The Other ◽  
Steric Effects ◽  
Molecular And Crystal Structures ◽  
Electronic And Steric Effects

The effect of 1,5-disubstitution on the photochemistry of 9,10-ethenoanthracene-11,12-diesters has been studied and correlated with the crystal structures determined for several derivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. The crystals studied are: (1)-Cl, dimethyl 1,5-dichloro-9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate, C20H14Cl2O4, P21/n; (1)-CN, 1,5-dicyano derivative, C22H14N2O4, P21/n; (1)-CN.0.5p-xylene, C22H14N2O4.0.5C8H10, P21/c; (1)-CN.xxylene, C22H14N2O4.xC8H10, P21/n; (1)-OMe, 1,5-dimethoxy derivative, C22H20O6, P{\bar 1}; (2b)-Cl, C20H14C12O4, dimethyl 1,5-dichloro-4b,8b,8c,8d-tetrahydrodibenzo[a, f]cyclopropa[c,d]pentalene-8c,8d-dicarboxylate, Pna21. The dibenzobarrelene molecules all have geometries and dimensions similar to those of related materials. In particular, the orientations of the two ester groups in each molecule differ, one being in general almost fully conjugated with the C(11)=C(12) double bond and the other almost non-conjugated. Relationships are sought between the ratios of the two regioisomeric photoproducts and molecular and crystal structures; both electronic and steric effects are considered, but no one effect seems to dominate.

scholarly journals Carbonyl Addition Reactions: Factors Affecting the Hydrate–Hemiacetal and Hemiacetal–Acetal Equilibrium Constants

1975 ◽  
Vol 53 (6) ◽  
pp. 898-906 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Compounds ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Steric Effects ◽  
Addition Reactions ◽  
Free Energies ◽  
Electronic Effects ◽  
Factors Affecting ◽  
Analogous Formula

Equilibrium constants for hydrate–hemiacetal interconversion in aqueous solution at 25° have been measured for four fluorinated carbonyl compounds: compound, alcohol, K4 (M−1): CF3CHO, C2H5OH, 2.3; CF3COCH3, CH3OH, 1.0; CF3COPh, CH3OH, 3.5; CF3COCF3, CH3OH, 0.14. These values, combined with values from the literature, permit an examination of substituent effects upon the equilibrium constant for[Formula: see text]The free energy change for this process, corrected for symmetry and steric effects, follows the equation[Formula: see text]Thus electronic effects upon this equilibrium are generally small and in fact are often smaller than steric effects.This analysis permits and justifies the calculation of free energies of formation of [Formula: see text] compounds from the (more generally measurable) free energies of formation of the analogous [Formula: see text] compounds.

Synthesis of dipyroromethanes in water and investigation of electronic and steric effects in efficiency of olefin epoxidation by sodium periodate catalyzed by manganese tetraaryl andtransdisubstituted porphyrin complexes

2019 ◽  
Vol 23 (06) ◽  
pp. 671-678 ◽  
Author(s):  
Mojtaba Bagherzadeh ◽  
Mohammad Adineh Jonaghani ◽  
Mojtaba Amini ◽  
Anahita Mortazavi-Manesh
Keyword(s):  
Catalytic Activity ◽  
Reaction Time ◽  
Sodium Periodate ◽  
Acid Catalyst ◽  
Steric Effects ◽  
Electronic Effects ◽  
Good Catalytic Activity ◽  
Epoxidation Of Alkenes ◽  
Epoxidation Of Olefins ◽  
Electronic And Steric Effects

Condensation of pyrrole with various aldehydes in the presence of BF3•etherate as an acid catalyst in water provides good yield of some dipyrromethanes. Prolongation of the reaction time with aldehydes substituted by electron-donating (mesityl) or electron-withdrawing (2,6-dichlorophenyl) groups on the ortho positions of the phenyl did not lead to decomposition or scrambling. Manganese trans disubstituted porphyrin complexes which derive from various dipyrromethanes and manganese tetraaryl porphyrin complexes including various substituents with different steric and electronic properties show good catalytic activity in epoxidation of alkenes by NaIO4in the presence of imidazole (ImH). The study of steric and electronic effects of the catalysts on the epoxidation of olefins shows that Mn-porphyrin complexes with more bulky and electron-releasing groups on meso phenyls could increase the epoxidation yield of most alkenes.

Asymmetric induction in the additions of anions of allylic sulfoxides to benzaldehyde

1980 ◽  
Vol 33 (12) ◽  
pp. 2635 ◽  
Author(s):  
DJ Antonjuk ◽  
DD Ridley ◽  
MA Smal
Keyword(s):  
Double Bond ◽  
Sigmatropic Rearrangement ◽  
Asymmetric Induction ◽  
Addition Reactions

Addition reactions of anions of aryl allyl sulfoxides to benzaldehyde proceed readily in moderate yields and afford mixtures of products resulting from α- and γ-attack on the allyl anion. The γ-products all possess the (E)-configuration around the double bond, and asymmetric induction occurs in the addition to the extent that the major/minor diastereomer ratio exceeds 2 : 1, generally. Electronic factors are believed to be responsible for this 'remote' asymmetric induction. Mixtures of all four possible diastereomers are observed in the products from α-attack and evidence is presented which suggests that the ratios of these products are as a result of epimerization of two of the chiral centres by [2,3] sigmatropic rearrangement.

Configuration on the C=N double bond of monosubstituted amidines and amidoximes

1989 ◽  
Vol 54 (12) ◽  
pp. 3245-3252 ◽  
Author(s):  
Bernard Tinant ◽  
Janine Dupont-Fenfau ◽  
Jean-Paul Declercq ◽  
Jaroslav Podlaha ◽  
Otto Exner
Keyword(s):  
Double Bond ◽  
Nitrogen Atom ◽  
Steric Effects ◽  
Model Compounds ◽  
X Ray ◽  
Analogous Model

Configuration on the C=N double bond of amidines and amidoximes is controlled by steric effects on the second nitrogen atom but there is a difference in the case of N’-monosubstituted derivatives: amidines prefer E configuration (conformation around the C-N bond sp) and amidoximes Z configuration (conformation ap). This was confirmed by the X-ray structures of two analogous model compounds N,N’-dimethyl-4-nitrobenzamidine (monoclinic, P21c, a = 10.855(3), b = 11.043(3), c = 8.593(3) Å, β = 105.69(2)°, V = 991.8(5) Å3, Z = 4, Dx = 1.29 g cm-3, CuKα, λ = 1.5418 Å, μ = 7.91 cm-1, F(000) = 408, T = 291 K, R = 0.065 for 1 265 observed reflections) and N’-methyl-4-nitrobenzamidoxime (monoclinic, P21/a, a = 6.699(2), b = 24.178(9), c = 6.075(2) Å, β = 106.20(3)°, V = 944.9(6) Å3, Z = 4, Dx = 1.37 g cm-3, CuKα, λ = 1.5418 Å, μ =9.22 cm-1, F(000) = 408, T = 291 K, R = 0.079 for 1 278 observed reflections).

Sign in / Sign up

Export Citation Format

Share Document