Vedrenne, Emeline (2006) Towards the total synthesis of Paulitin - New insights into metathesis reactions. Thesis, ?? institution/ep ??.

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Abstract

THE AIM OF THIS WORK WAS INITIALLY THE TOTAL SYNTHESIS OF PAULITINE. THE RESULTS OBTAINED LEAD US TO STUDY THE ENYNE-METATHESIS MECHANISM IN MORE DETAIL, IN ORDER TO OBTAIN THE A-B BICYCLE OF THE TARGET MOLECULE. IT WAS THEN HIGHLIGHTED THAT, FOR ENYNES WITH A TERMINAL ALKYNE AND AN OXYGEN ATOM AT THE PROPARGYLIC POSITION, THE RUTHENIUM CARBENE FIRST ! REACTS WITH THE ALKYNE. STERIC HINDRANCE AT THE PROPARGYLIC PO! SITION S EEMS TO INFLUENCE STRONGLY THE YIELD OF THE METATHESIS: CYCLIZATION IS MUCH EFFICIENT WHEN IT DECREASED. A DESMETHYL PRECURSOR OF THE TARGET BICYCLE WAS THEN OBTAINED IN SEVEN PERCENTS OVER EIGHT STEPS. ASYMMETRIC SYNTHESIS OF THE BICYCLE AS WELL AS FORMATION OF ALPHA-METHYLENE-GAMMA-BUTYROLACTONES WERE THEN STUDIED.PARALLEL TO THIS WORK, A NEW METHODOLOGY WAS DEVELOPED FOR THE METATHESIS OF ALLYLIC AMINO COMPOUNDS, WHICH ARE GENERALLY POOR METATHESIS-PARTNERS. THE USE OF BORON-BASED LEWIS ACIDS, ALLOWED TO CLEANLY OBTAIN COUPLING PRODUCTS. THIS NEW METHOD GAVE ACCESS TO A WIDE RANGE OF FUNCTIONALIZED OLEFINS, IN GOOD YIELDS, WHEN REACTIONS WERE LED IN REFLUXING TOLUENE FOR TWELVE HOURS, USING FIVE PERCENTS OF HOVEYDA-BLECHERT CATALYST AND ONLY ONE EQUIVALENT OF METATHESIS-PARTNER.

Item Type:Thesis (Thesis)
Uncontrolled Keywords:Steric hindrance
Subjects:Chemistry, Physical Chemistry and Chemical Engineering
Divisions:
ID Code:1926
Deposited By:Laurence Vidament
Deposited On:26 avr. 2007 02:20
Dernière modification:05 juin 2013 09:13

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