A visible-light-mediated procedure for the unprecedented trifluoromethylchlorosulfonylation of unactivated alkenes is presented. It uses [Cu(dap)2]Cl as catalyst, and contrasts with [Ru(bpy)3]Cl2, [Ir(ppy)2(dtbbpy)]PF6, or eosin Y that exclusively give rise to trifluoromethylchlorination of the same alkenes. It is assumed that [Cu(dap)2]Cl plays a dual role, that is, acting both as an electron transfer reagent as well as coordinating the reactants in the bond forming processes.
A photoredox-catalyzed
procedure for the iodoperfluoroalkylation
of styrenes and phenylacetylenes using readily available copper phenanthroline
catalyst is reported. In contrast to commonly employed [Ru(bpy)3]Cl2, [Ru(phen)3]Cl2 or fac-Ir(ppy)3, [Cu(dap)2]Cl is capable
to convert styrenes to the corresponding perfluoroalkyl tagged ethylbenzenes,
pointing toward an additional role of the copper catalyst beyond photoinduced
electron transfer. An inner sphere catalytic cycle involving Cu(III)
intermediates or ligand abstraction from a [CuI]+ intermediate
is proposed.
A series of heteroleptic [Cu(phenantroline)(bisisonitrile)] + -complexes was synthesized and their structural, spectroscopic and electrochemical properties were investigated. The new copper(I) complexes were employed as photoredox-catalysts in the visible light-mediated atom transfer radical addition (ATRA). Especially [Cu(dpp)(binc)]BF4 (6a-BF4) (dpp = 2,9-diphenyl-1,10-phenanthroline; binc = bis(2-isocyanophenyl) phenylphosphonate) proved to be highly active owing to an enhanced excited state lifetime compared to the commonly employed [Cu(dap)2]Cl (1-Cl) (dap = 2,9-di(p-anisyl)-1,10-phenanthroline). Furthermore, the catalyst could be applied to allylation reactions with trimethylallylsilane under mild visible-light photoredox conditions.
A photo-redox-catalyzed procedure for the one-step formation of sultones from α,ω-alkenols and trifluoromethylsulfonyl chloride is described. Using [Cu(dap)2]Cl (1 mol %), a wide range of substrates can be cleanly converted to the target compounds, while commonly employed photoelectron transfer catalysts such as [Ru(bpy)3]Cl2 or fac-Ir(ppy)3 fail in this transformation. The obtained fluorinated sultones are attractive as potential electrolyte additives or as structural motifs in drug synthesis, with the latter being demonstrated with the synthesis of a trifluoroethyl-substituted analogue of a benzoxathiin that has high anti-arrhythmic activity.
Die Trifluormethylchlorsulfonierung von Alkenen gelingt durch die Kombination von sichtbarem Licht und [Cu(dap)2]Cl als Photoredoxkatalysator. Im Gegensatz dazu katalysieren [Ru(bpy)3]Cl2, [Ir(ppy)2(dtbbpy)]PF6 oder Eosin Y eine Trifluormethylchlorierung. [Cu(dap)2]Cl spielt in diesem Prozess eine zweifache Rolle: Einerseits agiert es als Elektronentransferreagens, andererseits koordiniert es die Reagentien für die Bindungsbildung.
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