Abstract
γ-Effects of group 14 elements such as silicon and tin is discussed with the emphasis on the comparison with β-effects. Based on the striking γ-effect of tin, cyclopropantion reactions of alkenes using organotin compounds have been developed. Using allyl group 14 element compounds as alkenes, intramolecular competition between β-elimination and γ-elimination of group 14 elements has been studied. Intermolecular competition has also been examined using the reaction of allyl- and homoallyl group 14 element compounds with electrophiles. As an application of the present method in organic synthesis, intramolecularization of cationic cyclopropanation based on in-situ transacetalization to form unique cyclopropane structures is demonstrated.
1 Introduction
2 Control of Carbocationic Reactions Using Group 14 Elements
2.1 β-Effect of Silicon
2.2 β-Effect and γ-Effect of Group 14 Elements
2.3 γ-Elimination of Group 14 Elements
3 Carbocationic Cyclopropantion of Alkenes Using Tin
3.1 Carbocationic Cyclopropanation of Alkenes Using Tin-Substituted Carbonates
3.2 Carbocationic Cyclopropanation of Alkenes Using Tin-Substituted Acetals
4 Intramolecular Competition between β-Effect and γ-Effect of Group 14 Elements
5 Intermolecular Competition between β-Effect and γ-Effect of Group 14 Elements
6 Intramolecularization of Carbocationic Cyclopropanation Using Tin
7 Conclusion
Key words
carbocationic carbon-carbon bond formation - cyclopropanation - γ-effect - organotin compounds