Free radical additions. part VII. free radical addition of bromomalononitrile to alkenes; relative rate constants

Riemenschneider, K.; Drechsel-Grau, Edgar; Boldt, Peter

doi:10.1016/s0040-4039(01)85919-0

Cited by 6 publications

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“…Polar and stabilization effects greatly depend on the nature of substituents present on both the radical and the radical acceptor. , Results reported for electrophilic substituted alkyl radicals indicate that the addition to alkene double bonds is dominated by SOMO/HOMO interaction and, therefore, is favored by alkene electron-releasing substituents . In contrast, the addition to alkyne triple bonds appears to be either SOMO/HOMO- or SOMO/LUMO-controlled, depending on the nature of the alkyne substituent. 7d, Thus it is favored by both strong electron-releasing and strong electron-withdrawing (EWG) alkyne substituents 7d. On the contrary, non-EWG-substituted alkyl radicals, which are nucleophilic in character, preferentially add to EWG-substituted alkenes and alkynes …”

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Substituent Effects on Vinyl Radical Cyclizations onto Aryl Rings

Montevecchi

Navacchia

1998

J. Org. Chem.

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Regioselective toluenesulfanyl radical addition to the C-1 carbon of propynyl benzyl ethers 2a-i leads to vinyl radicals 3a-j which mainly give methyl sulfides 9a-j and methyl ethers 8a-j through stereoselective 5-(pi-endo)exo and 5-(pi-exo)exo cyclization, respectively. Additionally, minor amounts of pi-endo 6-membered cyclization products 5a-j and hydrogen abstraction products 4a-j are also formed. The role of steric and stereoelectronic factors in the 5-membered vs 6-membered and pi-endo vs pi-exo cyclization as well as the role of stabilization and polar factors has been studied. The substituent effect on the 5-(pi-exo)exo cyclization has been estimated by the relative rate constants, k(R), calculated for several substituents in the 4- and 3-position. Results show that stabilization and polar factors slightly affect the rate of the vinyl radical cyclization onto arene rings, which appears to be rather unselective with respect to the nature of the substituent. The nature of polar effects indicates that vinyl radicals are slightly electrophilic in character.

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confidence: 99%

Substituent Effects on Vinyl Radical Cyclizations onto Aryl Rings

Montevecchi

Navacchia

1998

J. Org. Chem.

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Limitations of the Reactivity—Selectivity Principle. Application to Free Radical Addition to Alkenes and Nucleophilic Aliphatic Substitution

Pross

1985

Israel Journal of Chemistry

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The limitations of the reactivity—selectivity principle (RSP) are discussed in terms of the qualitative configuration mixing (CM) model. It is concluded that the RSP is expected to break down for cases in which the reaction transition state takes on character largely absent in reactants or products, though not all breakdowns of the RSP are attributed to this cause. This conclusion is illustrated with two model reactions that do not follow the RSP: (a) radical addition to alkenes, and (b) nucleophilic aliphatic substitution. Analysis leads us to agree with previous statements by Jencks and Arnett that the RSP should be abandoned as a predictive tool.

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Part 1

Lorand¹

Carbon-Centered Radicals I

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Free radical additions. part VII. free radical addition of bromomalononitrile to alkenes; relative rate constants

Cited by 6 publications

References 6 publications

Substituent Effects on Vinyl Radical Cyclizations onto Aryl Rings

Substituent Effects on Vinyl Radical Cyclizations onto Aryl Rings

Limitations of the Reactivity—Selectivity Principle. Application to Free Radical Addition to Alkenes and Nucleophilic Aliphatic Substitution

Part 1

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