|M.Sc Student||Abramovich Adi|
|Subject||Zinc Homologation of SP3 Organometallic Alpha to Sulfoxide|
A new Synthesis of Olefins
|Department||Department of Chemistry||Supervisor||Professor Ilan Marek|
Chiral sulfoxides are very efficient chiral auxiliaries that are inducing
important asymmetric transformations. However, in most of the applications,
sulfoxides are only chiral synthetic tools and must be disposed of at the end
of the sequence. Recently, it was discovered in our research group a new
preparation for polysubstituted allenes starting from alkynyl sulfoxide. It
involves a sequence of carbocupration, intermolecular zinc homologation
followed by a syn β-elimination reaction.
Considering only the β-elimination step, we have a new way to eliminate the sulfoxide moiety. Therefore, by using the same principle, we were interested to develop this new concept of zinc homologation followed by a β-elimination reaction for the elimination of sp3 sulfoxide.
In this work, we have successfully developed two approaches for the transformation of sp3 sulfoxide into alkenes.
The first approach consists in the intermolecular reaction between α-sulfinyl organocopper derivatives and the Simmons-Smith-Furukawa zinc carbenoids. In this particular reaction, primary sulfoxides react easily with primary and secondary zinc carbenoids.
A second approach consists in the intramolecular reaction between α-sulfinyl lithium derivatives and the same zinc carbenoids. This approach is also very attractive not only because stoichiometric amounts of reagents are used but more importantly because it represents the only possibility to transform secondary sulfoxides into olefins.
In the last part of our work, we have designed few applications of our methodology for the preparation of chiral molecules. For instance, the preparation of chiral β-hydroxy sulfoxide has been easily achieved and their transformations into chiral allylic alcohols are currently underway.