Abstract
Iron- and cobalt-catalyzed Sonogashira coupling reactions are becoming central areas of research in organic synthesis. Owing to their significant importance in the formation of carbon–carbon bonds, numerous green and nanoparticle protocols have emerged during the past decades. The non-toxic and inexpensive nature of catalysts gained much attention in recent times. In this context, their catalytic nature and activity in Sonogashira coupling reactions were well explored and compared. Most importantly, one of the highlights of this review is the emphasis given to green strategies. This is the first review on iron- and cobalt-catalyzed Sonogashira coupling reactions which comprehends literature up to 2020.
Highlights
The palladium-catalyzed cross-coupling reaction between an aryl/vinyl halide (Cl, Br, I, OTf) and a terminal alkyne in the presence of a Cu(I) co-catalyst under basic conditions to form a Csp2–Csp bond generating an arylalkyne is known as the Sonogashira (Sonogashira–Hagihara) coupling [1] and has become an important C–C bond-forming reaction [2]
Over the past 15 years, there has been a growing interest in the Sonogashira coupling reaction, which is one of the most powerful methods for the formation of Csp2–Csp bonds leading to arylalkynes and conjugated alkenynes, which are often intermediates or precursors in the synthesis of natural products, pharmaceuticals of biological activity, and materials science [3]
A Sonogashira-type coupling reaction between aryl halides and terminal alkynes in aqueous medium in the presence of hollow palladium-cobalt bimetallic nanoparticles was reported by Li et al (Scheme 29) [42]
Summary
The palladium-catalyzed cross-coupling reaction between an aryl/vinyl halide (Cl, Br, I, OTf) and a terminal alkyne in the presence of a Cu(I) co-catalyst under basic conditions to form a Csp2–Csp bond generating an arylalkyne is known as the Sonogashira (Sonogashira–Hagihara) coupling [1] and has become an important C–C bond-forming reaction [2]. Anilkumar and co-workers reported an iron-catalyzed Sonogashira coupling of aryl iodides with terminal alkynes in the presence of a catalytic system made up of the greenest solvent, water, in the presence of 10 mol % FeCl3·6H2O and 20 mol % 1,10-phenanthroline as ligand under aerobic conditions [13]. Heterogeneous green protocols Rizi and co-workers reported a silica-supported green heterogeneous Fe(III) catalyst for the cross-coupling reaction of aryl iodides and arylacetylenes in good yields (Scheme 4) [23].
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