Development of Catalytic ElectrophilicTrifluoromethylation and Fluorination Methods
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
This thesis is focused on development of new catalytic, electrophilic fluorination and trifluoromethylation methods of alkenes. These reactions were carried out using hypervalent trifluoromethyl and fluoroiodine reagents.
The first project involved copper catalyzed oxytrifluoromethylation of terminal alkenes and alkynes. In this reaction the employed hypervalent iodine underwent a formal addition to C-C multiple bonds. Subsequently, we have also shown that under similar reaction conditions in the presence of B2pin2 as additive quinones can smoothly undergo C-H trifluoromethylation.
We also developed a cyanotrifluoromethylation reaction of styrenes, which proceds in the presence of copper cyanide and PCy3 as additive. This reaction allows addition of both trifluoromethyl and cyanofunctionality to the styrene, creating two new carbon-carbon bonds.
The interesting substituent effects and the acceleration of B2pin2 and PCy3 additives inspired us to further investigate the mechanism for the above trifluoromethylation reactions. The Hammett studies showed that the oxytrifluoromethylation reactions are slightly accelerated by electron donor substituents. The C-H trifluoromethylation does not show deuterium isotope effect. Both B2pin2 and PCy3 accelerated the trifluoromethylation reactions but the extent of the acceleration was dependent on the reaction type and on the substituent effects.
Inspired by our trifluoromethylation results, we have also studied the silver-mediated difluorination of styrenes in the presence of an electrophilic hypervalent iodine based fluorine source. We obtained over 50% of the difluorinated product which suggests that one fluorine atom comes from the fluoroiodine reagent and the other one from BF4-. A phenonium ion intermediate has been proposed to be involved in the mechanism of the difluorination reaction.
Place, publisher, year, edition, pages
Stockholm University, 2014. , 44 p.
IdentifiersURN: urn:nbn:se:su:diva-109867OAI: oai:DiVA.org:su-109867DiVA: diva2:767542
2014-12-16, 14:00 (English)