Nucleophilic Neighboring Group Participation

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Nucleophilic Neighboring Group Participation
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Nucleophilic Neighboring Group Participation

• Case I Rationale

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Nucleophilic NGP

• Case II

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Nucleophilic NGP

• Case III

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Non-nucleophilic NGP

• Acetolysis of Phenyl tosylates

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Possible explanations for the results of the
acetolysis reactions

• Direct bimolecular nucleophilic attack at C-2
• Inconsistent with the experimental data. Why?
• Formation of a secondary carbocation at C-2
• Inconsistent with the experimental data. Why?

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Rapidly equilibrating secondary carbocations to
account for the acetolysis results?

• The Windshield-Wiper Effect

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Additional data concerning acetolysis of phenyl
tosylates

• Fact One - Scrambling of a label

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Additional data concerning acetolysis of phenyl
tosylates

• Fact Two - Substituent effects

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Additional data concerning acetolysis of phenyl
tosylates

• Fact Three - Formation of Spirane products

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Additional data concerning acetolysis of phenyl
tosylates

• Fact Four - Unusual Kinetics

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Explanation to account for the acetolysis results

• Phenonium ion participation

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Alkyl Participation

• ? - bridged complexes

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Corroborating evidence for alkyl participation
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Open carbocation possibility
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Methyl bridged intermediate
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Data for the solvolysis of cyclohexyl tosylates
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Rationale for cyclohexyl tosylate solvolysis
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Rationale for cyclohexyl tosylate
solvolysiscontd.

• ?-Hydrogen participation

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Solvolysis of unsaturated tosylates
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Possible explanations for solvolysis of
unsaturated tosylates