Alkenes building block trifluoromethylation

Pyridyldimethylsilane 24 is a reagent for the metal-catalyzed hydrosilylation of alkynes and alkenes <2004EROS1>. 4-(Trifluoromethyl)pyridine 25 has been used as a building block in heterocycle synthesis <2005EROS1>. 

Photochemical k 280-300 nm) or thermal (>150 °C) decomposition of trifluoromethyl-sub-stituted diazo compounds 1 or diazirines 2 in the presence of excess alkene (acyclic or cyclic) yielded trifluoromethylcyclopropanes 3 and 4 in low to moderate yield (for examples see Houben-Weyl, Vol. E19b, p 1026). When the building block has two different substituents, the cyclopropane diastereomer resulting from the smaller steric interactions between the reactants is formed preferentially. 

As mentioned in the previous section, trifluoromethylated alkenes are promising building blocks for pharmaceuticals, agrochemicals, and functional materials [112-116]. But reported synthetic methods via trifluoromethylation exhibited limited substrate scopes with respect to hetero-aromatics and functional groups [117-121]. We found that application of potassium vinyltrifluoroborates 23, which are regarded as electron-rich alkenes, to our photocatalytic oxytrifluoro-methylation leads to efficient formation of trifluoromethylated alkenes 24 via deboronation. We revealed that our photoredox-catalyzed protocol for construction of Caikenyi-CF3 bonds exhibits broad scope in an efficient and stereoselective manner. 

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