I  U  P  A  C






News & Notices

Organizations & People

Standing Committees

Divisions

Projects

Reports

Publications
..CI
..PAC
..Macro. Symp.

..Books
..Solubility Data

Symposia

AMP

Links of Interest

Search the Site

Home Page

 

Pure Appl. Chem., Vol. 72, No. 9, pp. 1671-1683, 2000.

 

 

Stereoselective and enantioselective synthesis of five-membered rings via conjugate additions of allylsulfone carbanions*

Alfred Hassner**, Eugene Ghera, Tamar Yechezkel, Victoria Kleiman, Thiagarajan Balasubramanian, and Daryl Ostercamp

Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel

Abstract: This lecture describes some of our studies of lithio derivatives of allyl sulfone carbanions which add a-regioselectively as well as anti diastereoselectively to Michael acceptor olefins. This can be ascribed to chelation in the Michael addition step. When the reaction leads to subsequent ring closure by using a bromoallyl sulfone, the latter acts as a methylenemethane synthon in a (3+2) Michael-initiated ring closure, affording highly functionalized cyclopentane derivatives. Such additions proceed with high stereoselectivity and with asymmetric induction leading to nonracemic substituted cyclopentanones. Additions of allyl sulfone carbanions also proceed stereoselectively to C=N systems containing a chiral auxiliary on N. These can be used in the synthesis of optically active five- and six-membered ring N-heterocycles. Furthermore, chiral groups on the allyl sulfone moiety can induce significant remote asymmetric induction, made possible by the presence of an aromatic p-system which promotes intramolecular chelation to the Li cation.

*Lecture presented at the 13th International Conference on Organic Synthesis (ICOS-13), Warsaw, Poland, 1-5 July 2000.
** Corresponding author

Back to Contents for access to full text


Page last modified 15 January 2001.
Copyright ©2000-2001 International Union of Pure and Applied Chemistry.
Questions or comments about IUPAC, please contact, the Secretariat.
Questions regarding the website, please contact web manager.