Effects of B(2)pin(2) and PCy3 on copper-catalyzed trifluoromethylation of substituted alkenes and alkynes with the Togni reagent
2015 (English)In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 71, no 6, 922-931 p.Article in journal (Refereed) Published
The copper-catalyzed oxytrifluoromethylation of phenylacetylenes and C-H trifluoromethylation of quinones were studied. It was found that both reactions are accelerated by B(2)pin(2) and PCy3 additives. The two reactions have different substituent effects. The oxytrifluoromethylation is faster in the presence of electron-donating groups, while the C-H trifluoromethylation is faster with electron-withdrawing substituents. The Hammett plot for oxytrifluoromethylation gave a rho value of 0.76 indicating electron demand in the rate determining step of the reaction. According to the absolute value of rho the reaction probably does not proceed through a rate determining formation of a carbocation intermediate. The kinetic isotope effect measurements indicate that in C-H trifluoromethylation of quinones the cleavage of the C-H bond is not the rate determining step of the reaction.
Place, publisher, year, edition, pages
2015. Vol. 71, no 6, 922-931 p.
Catalysis, Trifluoromethylation, Substituent effects, Hammett plot, Quinones
IdentifiersURN: urn:nbn:se:su:diva-115277DOI: 10.1016/j.tet.2014.12.077ISI: 000348950300003OAI: oai:DiVA.org:su-115277DiVA: diva2:799821