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Fluoride-Triggered Synthesis of 1‑Aryl-2,2-difluoroalkenes via Desilylative Defluorination of (1-Aryl)-2,2,2-trifluoroethyl-silanes
journal contributionposted on 2021-09-03, 20:06 authored by Virginie Carreras, Thierry Ollevier
An efficient route for the synthesis of 1-aryl-2,2-difluoroalkenes via 1,2-desilylative defluorination is disclosed. Only a catalytic amount of fluoride source is required to initiate the desilylation and afford gem-difluoroalkenes in very good to quantitative yields, using mild reaction conditions in dimethyl carbonate as a green solvent. This reaction uses (1-aryl)-2,2,2-trifluoroethyl-silanes, which are easily prepared via the insertion reaction of trifluoroethyl diazo alkanes into the Si–H bond of tertiary organosilanes. (1-Aryl)-perfluoroalkyl-silanes cleanly afford the corresponding (Z)-1-benzylideneperfluoroalkanes, which upon hydrodefluorination furnish the (E)-β(perfluoroalkyl)styrene derivatives with excellent yield and complete stereoselectivity. A one-pot system involving sequential insertion and desilylative–defluorination is also suitable for this transformation. This method demonstrates the usefulness of organosilanes toward the preparation of fluorinated alkenes as synthetically useful targets.
synthetically useful targetseasily prepared viadesilylative – defluorinationdifluoroalkenes via 11 ‑ arylaryl )- 2silanes cleanly afforddesilylative defluorination>- difluoroalkenes>)- 1z tertiary organosilanesreaction usesquantitative yieldsorganosilanes towardmethod demonstratesinsertion reactiongreen solventgem fluorinated alkenesexcellent yieldefficient routee dimethyl carbonatecomplete stereoselectivitycatalytic amountalso suitable