A Sustainable, User‐Friendly Protocol for the Pd‐Free Sonogashira Coupling Reaction

Abstract

We herein present a new catalytic system for the palladium‐free Sonogashira coupling reaction. The catalytically active moiety is formed in situ, in a straightforward and user‐friendly manner, by combining a widely available low‐cost copper salt and an N‐heterocyclic carbene precursor. A series of N‐heterocyclic carbene ligand precursors with variable structural features, some of which are novel, were tested and the reaction conditions were optimized. Using the catalytic system with the optimum performance, the scopes of the alkyne and the aryl halide were probed. Aryl iodides readily react with terminal alkynes, providing the coupling products in high to excellent yields. The protocol is highly efficient with alkynes bearing either alkyl or aryl substituents, the latter having either electron‐donating or electron‐withdrawing groups.

Manganese‐Catalyzed Multicomponent Synthesis of Tetrasubstituted Propargylamines: System Development and Theoretical Study

“…[107] To the best of our knowledge, manganese catalysis has not yet been tested in the KA 2 coupling. Inspired by the applications of sustainable metal catalysis in green organic transformations, [35,[108][109][110][111] as well as our recent work on zinc catalysis, [81] we became interested in studying the potential of manganese catalysis in the KA 2 reaction. Our primary goal was the development of a highly-efficient, green, and user-friendly catalytic system based on a widely-available and cost-efficient manganese source, which could mediate the KA 2 coupling reaction of various challenging and syntheti-cally intriguing substrates, under solvent-free conditions.…”

Carbazole‐Based N‐Heterocyclic Carbenes for the Promotion of Copper‐Catalyzed Palladium‐Free Homo‐/Hetero‐Coupling of Alkynes and Sonogashira Reactions

“…Unsymmetrical diynes-via heterocoupling [18][19][20]37] of two different alkynes is a synthetic challenge that could be undertaken in a similar manner to that involving the heterocoupling of Grignard reagents, [34] Zinc reagents, [35] boronic acids. [36] An efficient way to promote the hetero-coupling-vs homo-coupling is to employ electronically distinct alkynes (i. e. electron-withdrawing and electron-donating substituents bearing alkynes) which modulates the electronic factors on the catalytically active metal center providing the hetero-coupled product preferentially over the homo-coupled one.…”

“…Copper catalysts in comparison to other metals have shown promising results at elevated temperature as reported by Lei et al, [13] Suib et al, [14] and several others. [15][16][17] Room temperature protocols by Cai et al, [18] Yao et al [19] and Hwang et al [20] further emphasized the persisting interest in such alkyne hetero-couplings. A closer inspection of these reports, however, suggests that the applied conditions are most often not suitable for reacting molecules withlabile functional groups or important biomolecules.…”

Facile Green Preparation of Rhodium Nanoclusters Supported Nano-Scaled Graphene Platelets for Sonogashira Coupling Reaction and Reduction of p-Nitrophenol

“…In fact, the catalytic conversion of hazardous 4-nitrophenol to valuable 4-aminophenol is a highly significant process in green chemistry [24]. Similarly, the transition metal catalyzed Sonogashira coupling reaction between terminal alkynes and aryl halides is a significant toolin organic synthesis [25]. The catalytic products can be used in pharmaceuticals and fine chemicals.…”