Regioselective and Redox‐Neutral Cp*Ir^III‐Catalyzed Allylic C−H Alkynylation

Abstract

Herein, we report a Cp*IrIII‐catalyzed highly regioselective and redox‐neutral protocol for the construction of 1,4‐enynes from unactivated olefins and bromoalkynes via intermolecular allylic C−H alkynylation. The developed mild reaction conditions tolerate a broad range of common functional groups, even enabling selective alkynylation of allylic C−H bonds in the presence of other prominent directing groups. Mechanistic experiments including the isolation of a catalytically active IrIII‐allyl species support an intermolecular allylic C−H activation followed by an electrophilic alkynylation.

Rhodium-catalysed ortho-alkynylation of nitroarenes

“…Here we report the Rh-catalysed nitro-directed C–H alkynylation of nitrobenzenes, which tolerates a broad range of functional groups ( Scheme 1c ). 11 Our experimental and computational mechanistic investigations are consistent with a turnover limiting electrophilic C–H activation step, followed by alkyne insertion and bromide elimination. We also disclose preliminary results on a related C–H iodination reaction, which may pave the way for other types of ortho -functionalization via sequential Rh/Pd catalysis.…”

Palladium-Catalyzed γ,γ′-Diarylation of Free Alkenyl Amines

“…Alkenes are important feedstocks in synthetic chemistry due to their versatility; they are inherently nucleophilic but can easily be made electrophilic by the addition of certain functional groups or catalysts. − Alkenes can also serve as activating groups for adjacent C–H bonds, allowing even greater synthetic utility. − One of the biggest challenges for alkene functionalization is to achieve regioselectivity. − While this is easily overcome for terminal olefins − and cyclization reactions, , internal alkenes often undergo poor regiochemically selective reactions without the aid of activating functional groups. This has spawned a significant research enterprise exploring how to achieve regioselective transformations in electronically unbiased alkenes. − For transition metal-catalyzed reactions, one of the most effective strategies has been the use of directing groups (DGs).…”

Studies on the Origin of the Stabilizing Effects of Fluorinated Alcohols and Weakly Coordinated Fluorine-Containing Anions on Cationic Reaction Intermediates

“…On the basis of the above-described research and other studies, − , we speculated that adding a weakly coordinated fluorine-containing anion like BF 4 – , PF 6 – , or SbF 6 – to a fluorinated alcohol could further stabilize electron-deficient reaction intermediates. However, we found that using these anions in common organic solvents such as dichloromethane does not promote polycyclization reactions.…”

“…In our previous studies , and in studies by other research groups, the effects of adding a BF 4 – , PF 6 – , or SbF 6 – salt to a fluorinated alcohol reaction medium were compared; in most cases, all three anions were found to enhance the yields of the reactions studied. However, there was no consistent pattern in the yield enhancement between reactions.…”