Carbocationic Cyclopropanation Using Tin

(gamma)-Effects of group 14 elements such as silicon and tin is discussed with the emphasis on the comparison with (beta)-effects. Based on the striking (gamma)-effect of tin, cyclopropantion reactions of alkenes using organotin compounds have been developed. Using ­allyl group 14 element compounds as alkenes, intramolecular ­ competition between (beta)-elimination and (gamma)-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 (beta)-Effect of Silicon 2.2 (beta)-Effect and (gamma)-Effect of Group 14 Elements 2.3 (gamma)-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 (beta)-Effect and (gamma)-Effect of Group 14 Elements 5 Intermolecular Competition between (beta)-Effect and (gamma)-Effect of Group 14 Elements 6 Intramolecularization of Carbocationic Cyclopropanation Using Tin 7 Conclusion