Plausible Rh(V) Intermediates in Catalytic C–H Activation Reactions

Abstract

Catalysis by defined transition-metal complexes has captivated the attention of the scientific community over the last decades. The well-documented utility of Rh(III) complexes in C−H activation reactions have enabled the development of a plethora of new catalytic methods. High-valent transition-metal species in C−H activation reactions were first predicted in palladium-based transformations. From those early studies, it was apparent that differences in reactivity and selectivity could be expected. By analogy, higher valent Rh(V) complexes could represent a new approach in C−H activation reactions and offer different opportunities to improve and broaden the current state-of-the-art in the field.

Efficient Synthesis of Arylated Furans by a Sequential Rh‐Catalyzed Arylation and Cycloisomerization of Cyclopropenes

“…After that, reductive elimination affords the intermediate L.I nsertion of the formed Rh I into O À Nbond generates the arylated product E.Inpathway (IV), the insertion of 2a into F affords the seven-membered rhodacycle intermediate H.T hen, both the Rh III -Rh I -Rh III and the Rh III -Rh V -Rh III pathways are possible depending on the oxidation of Rh by the OÀNb ond either before or after the reductive step. [17] Thekey step in this proposed pathway is the base-assisted anti b-H elimination which should have asubstantial KIE value and meanwhile the Rh is reduced. [18] Thea cetate ion or the acetamide in the system might act as abase.…”

Rhodium‐Catalyzed C(sp2)‐ or C(sp3)−H Bond Functionalization Assisted by Removable Directing Groups

“…[10,11] On the other hand, the functionalization of C(sp 3 )ÀHb onds is still underdeveloped. [39][40][41] Furthermore,atransient directing group directed C À H functionalization related to this Review was also reviewed by several research groups. Themajor progress made and the clearer understanding of the mechanistic aspects of C À Ha ctivation have also been reviewed.…”

“…Themajor progress made and the clearer understanding of the mechanistic aspects of C À Ha ctivation have also been reviewed. [39][40][41] Furthermore,atransient directing group directed C À H functionalization related to this Review was also reviewed by several research groups. [42][43][44][45] Avariety of transition-metal complexes including first, second, and third row,a nd even lanthanides have been used in directed CÀHfunctionalization reactions.Among them, the most popular are Fe,Co, Ni, Cu, Ru, Rh, Pd, and Ir catalysts.…”

Rhodiumkatalysierte sp2‐ und sp3‐C‐H‐Funktionalisierungen mit entfernbaren dirigierenden Gruppen

“…Da an diesem Forschungsgebiet ein reges Interesse besteht, legen derzeit zahlreiche Forschungsgruppen ihren Fokus auf die dirigierte Funktionalisierung von C(sp 2 )‐H‐ sowie C(sp 3 )‐H‐Bindungen . Wichtige Fortschritte und ein besseres Verständnis der mechanistischen Aspekte der C‐H‐Aktivierungschemie wurde bereits erreicht . Ferner wurde die durch eine transiente dirigierende Gruppe dirigierte C‐H‐Funktionalisierung, die ebenfalls in diesem Aufsatz diskutiert wird, von verschiedenen Forschungsgruppen aufgegriffen .…”