Weinreb Amide Directed Versatile C−H Bond Functionalization under (η⁵‐Pentamethylcyclopentadienyl)cobalt(III) Catalysis

Abstract

The (η -pentamethylcyclopentadienyl)cobalt(III) (Cp*Co )-catalyzed C-H bond functionalization of aromatic, heteroaromatic, and α,β-unsaturated Weinreb amides was explored. C-H allylation reactions with the use of allyl carbonate and a perfluoroalkene, oxidative alkenylation reactions with the use of ethyl acrylate, iodination reactions with the use of N-iodosuccinimide, and amidation reactions with the use of dioxazolones were catalyzed by Cp*Co(CO)I in the presence of a cationic Ag salt and AgOAc to afford various synthetically useful building blocks. Mechanistic studies of the C-H allylation disclosed that the C-H activation step was rate determining and virtually irreversible.

Catalytic Cleavage of the Amide Bond in Urea Using a Cobalt(III) Amino‐Based Complex

“…Recently, there has been an emerging interest in the catalytic activity of Cobalt (III) complexes . The mechanistic studies suggest catalytic activation via different kinds of interactions with diverse organic substrates .…”

A Concise Approach for the Synthesis of the ABCD Ring System of Alpkinidine

“…Once compound 6 was synthesized, it was subjected to deprotonation with NaHMDS to give a deep green coloration. Further treatment with ethyl 2‐iodobenzoate 8 a or 2‐iodo‐ N ‐methoxy‐ N ‐methylbenzamide 8 b failed to give expected the product 6 a . The result could be due to the failure of the stable anion 7 to react with a less electrophilic ester 8 a or Weinreb amide 8 b .…”

Recent Progress in the C−N Bond Formation via High‐Valent Group 9 Cp*M(III)‐Catalyzed Directed sp2 C−H Activation

“…This C−H amidation/annulation strategy was an advancement over the similar Rh(III)‐catalyzed reaction [16d] where only 2‐aryl modified quinazolinones was produced. In another report by Matsunaga et al ., [16e] various aromatic and heteroaromatic Weinreb amides 30 were reacted to afford anilide derivatives under the cobalt(III)‐catalysis (Scheme 11d). It is also noteworthy that acrylic acid‐derived Weinreb amide was employed in the reaction to offer (Z)‐selective enamide albeit in low yield.…”