title: Direct C-H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis.
abstract: BACKGROUND
  Trifluoromethylated alkene scaffolds are known as useful structural motifs in pharmaceuticals and agrochemicals as well as functional organic materials. But reported synthetic methods usually require multiple synthetic steps and/or exhibit limitation with respect to access to tri- and tetrasubstituted CF3-alkenes. Thus development of new methodologies for facile construction of Calkenyl-CF3 bonds is highly demanded.
  
  
  RESULTS
  The photoredox reaction of alkenes with 5-(trifluoromethyl)dibenzo[b,d]thiophenium tetrafluoroborate, Umemoto's reagent, as a CF3 source in the presence of [Ru(bpy)3](2+) catalyst (bpy = 2,2'-bipyridine) under visible light irradiation without any additive afforded CF3-substituted alkenes via direct Calkenyl-H trifluoromethylation. 1,1-Di- and trisubstituted alkenes were applicable to this photocatalytic system, providing the corresponding multisubstituted CF3-alkenes. In addition, use of an excess amount of the CF3 source induced double C-H trifluoromethylation to afford geminal bis(trifluoromethyl)alkenes.
  
  
  CONCLUSIONS
  A range of multisubstituted CF3-alkenes are easily accessible by photoredox-catalyzed direct C-H trifluoromethylation of alkenes under mild reaction conditions. In particular, trifluoromethylation of triphenylethene derivatives, from which synthetically valuable tetrasubstituted CF3-alkenes are obtained, have never been reported so far. Remarkably, the present facile and straightforward protocol is extended to double trifluoromethylation of alkenes.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Ren
authors.initials: R
authors.lastname: Tomita
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yasu
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Koike
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Munetaka
authors.initials: M
authors.lastname: Akita
keywords: electrophilic trifluoromethylating reagent; multi-substituted alkene; photoredox catalysis; radical reaction; trifluoromethylation