The nickel-mediated [3+2] cycloaddition of 2-trifluoromethyl-1-alkenes with alkynes afforded fluorine-containing multi-substituted cyclopentadienes in a regioselective manner. This reaction involves the consecutive two C-F bond cleavage of a trifluoromethyl or a pentafluoroethyl group through β-fluorine elimination.
The nickel-catalyzed defluorinative coupling of 2-trifluoromethyl-1-alkenes and alkynes with the aid of Et 3 SiH provides 1,1-difluoro-1,4-dienes under mild reaction conditions. This reaction involves selective allylic C(sp 3 )−F bond activation via β-fluorine elimination from nickelacyclopentenes.
The synthesis of difluoromethylene-containing heterocycles was achieved via the palladium-catalyzed 1,1-difluoroallylation of heteronucleophiles followed by intramolecular Heck reaction. The allylic substitution of 3-bromo-3,3-difluoropropene was regioselectively accomplished by heteronucleophiles without rearrangement to give the corresponding 1,1-difluoroallylated compounds whose Heck cyclization proceeded in a 5-exo manner to afford ring-difluorinated indolines and dihydrobenzofurans. Their defluorinative allylic substitution further provided 2-fluoroindoles and 2-fluorobenzofurans.
Highly efficient immobilized catalysts for continuous‐flow cross‐coupling reactions that show better productivity than those for the corresponding batch reactions are increasingly in demand. For practical use, such catalysts should have highly catalytic activity and high leaching resistance. To find catalysts suitable for continuous‐flow conditions, we have developed a consistent method for evaluating the catalytic performance of commercially available immobilized Pd catalysts. Monitoring of the change in turnover frequency over time under excess substrate loading conditions revealed the limitation of these catalysts. On the basis of the evaluation results, we have successfully developed a new immobilized Pd catalyst that exhibited highly efficient and robust catalytic performance.
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