McMaster University | Department of Chemistry

                                                Synthesis of ??lactones  

                                                Carlos Zepeda

This presentation explores the Tandem Evans Aldol?Lactonization(TEAL)route to prepare ?lactones, using thiazolidine?2?thiones as a (chiral) auxiliary. Condensation of the Nacylthiazolidinethione enolate with ketones at low temperature generates aldolateanion intermediates which spontaneously cyclize upon warming to give ??lactones. The novel feature of this route is that the thiazolidine?2?thione can both control the stereochemistry of the aldol component of this two?step process, and act as an efficient leaving group in the second, lactonization step. My thesis focuses on investigating whether the aldol and lactonization components of this reaction can be separated. Can a Lewis Acid catalyzed aldol, alongside the auxiliary give good diastereo and or enantio selectivity?

And can the resulting aldol adduct, with the auxiliary still attached, cyclize in a separate step? Since aldehydes do not work in the current TEAL methodology, this route also offers a novel approach to expand the TEAL?type reaction using aldehydes as opposed to ketones.

DATE:             Wednesday, January 20, 2010                     

TIME:             1:30 p.m.

PLACE:            ABB 163