Inductive and resonance effects of substituents on pi-face selection

Article Abstract:

The relative stability of the transition states for bond formation at a trigonal center depends not only on the size of the allylic ligands but also on their sigma- and pi-donor capability. Further experiments indicate that the inductive effect is not the sole substituent property which determines stereochemical bias and that the dependence of pi-face selection is not linear and not even monotonic. Introduction of an allylic heteroatom in the stereogenic center was not a simple replacement of one sigma-donor by another.

Analysis, Ligand binding (Biochemistry), Chemical bonds, Resonance, Resonance (Physics), Induced polarization

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Electronic control of facial selection in additions to sterically unbiased ketones and olefins

Article Abstract:

A number of factors contribute to stereofacial selectivity in additions to sterically unbiased systems. Studies indicate that orbital interactions operate in conjunction with electrostatic interactions in a large majority of substrates, including endo-substituted 7-norbornanones and 5-substituted adamantanones. Electrostatic effects influence the relative stability of the transition state for syn face addition. In general, the orbital effects are small in magnitude and are easily overwhelmed by steric factors.

Electrostatics, Electrochemistry, Molecular orbitals

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Rationalizing the regioselectivity in polynitroarene anionic sigma-adduct formation. Relevance to nucleophilic aromatic substitution

Article Abstract:

The regioselectivity of the nucleophilic aromatic substitution and the Vicarious Nucleophilic Substitution reactions for 1-X-2,4,6-trinitrobenzenes depends on the Meisenheimer adduct intermediate formation. The stereoelectronic stabilization of C-1 adduct, arising out of the thermodynamic changes during this reaction, is important for the patterns of regioselectivity. Different classes of regioselectivity and the process of the metamorphosis of the regioselectivity pattern are presented.

Aromatic compounds

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