Rhodium-Catalyzed, Remote Terminal Hydroarylation of Activated Olefins through a Long-Range Deconjugative Isomerization

Abstract

The Rh-catalyzed, remote terminal hydroarylation of active olefins at the C7-position of indoles and the ortho-position of indolines and anilines with the appropriate choice of a N-P Bu directing group through long-range deconjugative isomerization has been reported. This transformation not only overcomes the conjugate rule of Michael acceptors but also controls the positional selectivity of indoles, representing a significant advancement in both alkene isomerization and the C-H alkylation of indoles.

Iridium‐Catalyzed Direct C4‐ and C7‐Selective Alkynylation of Indoles Using Sulfur‐Directing Groups

“…[1] Accordingly,s ignificant research interest has been focused on the development of site-selective functionalization methods for indole derivatives,a nd transition-metal-catalyzed direct CÀHb ond transformation has recently been recognized as an attractive synthetic tool for late-stage functionalization. [2,3] Thei ndole core inherently offers six distinctive reaction sites for the catalysis.A mong these,s elective functionalization of the benzenoid fragment over the highly reactive C2and C3-positions has remained ac hallenge for the synthetic community.T oa ddress this issue,v arious catalytic protocols involving alkylation, [4] alkenylation, [5] arylation, [6] amination, [7] and borylation [8] have been developed with the aid of appropriate directing groups during the past decade.N evertheless,tothe best of our knowledge,there is still no method for the direct alkynylation onto the benzenoid core,w hereas the catalytic systems for the C2-and C3-positions are wellestablished using bromoalkynes or ethynylbenziodoxoles (R-EBX) as the alkynylating reagents (Scheme 1a,b). [9] Consid-ering numerous possible transformations and applications in click chemistry [10] of the alkyne functionality,n ovel synthetic methods that enable site-selective alkynylation for the indole periphery appear to be in high demand.…”

Jenseits von Friedel und Crafts: dirigierte Alkylierung von C‐H‐Bindungen in Arenen

“…Detaillierte mechanistische Untersuchungen offenbarten eine Veränderung des Mechanismus von einem linear-selektiven Ligand-auf-Ligand-Wasserstofftransfer hin zu einer verzweigt-selektiven carboxylatgestützten internen elektrophilen Substitution in Gegenwart des Carboxylatadditivs.E ine besonders effiziente und vielversprechende enantioselektive Version auf Basis einer chiralen Carbonsäure wurde vor kurzem beschrieben. [195] [195] …”

PIII‐Chelation‐Assisted Indole C7‐Arylation, Olefination, Methylation, and Acylation with Carboxylic Acids/Anhydrides by Rhodium Catalysis

“…Although the detailed mechanism of the reaction remains unclear, we propose at entative catalytic cycle as shown in Figure 2. [16] Rhodium A coordinates first to the P III atom of the indole 1,l eading to the formation of complex B.A reversible cyclometalation through an anion-assisted deprotonation [17] at the indole C7 position delivers the intermediate C,w hich induces oxidative addition to generate the Rh III H species D. [11] Elimination of intermediate D gives the rhodacycle E.Then oxidative addition of the carboxylic anhydrides 2 or 4' ' to E affords the intermediate F.S ubsequent decarboxylation can yield the rhodium species G.Further reductive elimination and dissociation delivers the final products and regenerates the active catalyst. At al ower temperature, decarboxylation can be inhibited from acylrhodium complex F affording the acylation products by reductive elimination.…”