Visible‐Light‐Assisted Cobalt‐2‐(hydroxyimino)‐1‐phenylpropan‐1‐one Complex Catalyzed Pd/Cu‐Free Sonogashira–Hagihara Cross‐Coupling Reaction

Abstract

An effective and inexpensive strategy for the Co(C9H9NO2)3 catalyzed Sonogashira–Hagihara cross‐coupling reaction of aryl bromides containing electron‐rich and electron‐poor substituents with terminal alkynes was demonstrated. The reaction proceeded smoothly in the presence of ethylene glycol as additive and K2CO3 as base in DMF under visible light illumination, and 23 alkyne products were afforded in moderate to excellent yields, including four new diaryl ethynes. Compared with the high‐cost palladium catalyst, cobalt is an inexpensive catalyst with a preponderance of technologized production, and the palladium/copper‐free catalytic system not only provided an efficient process with mild reaction conditions, but also enhanced the substrate group tolerance.

Sulfonated salicylidene thiadiazole complexes with Co (II) and Ni (II) ions as sustainable corrosion inhibitors and catalysts for cross coupling reaction

“…Based on the reported typical mechanisms of C―C and C―N cross couplings, the catalytic cycle started with formation of the active catalyst complex intermediate ( I ) by reduction of Ni 2+ ion to Ni 0 in Ni‐Sanp, and Co 2+ ion to Co 0 in Co‐Sanp within electron transfer . Both phenyl boronic acid or aryl amine and the excess K 2 CO 3 could be the reason for the reduction and formation of I .…”

“…The proposed square planar geometry of Ni‐Sanp forced the reduction of Ni 2+ ion and the substrate attack of halopyridine to the reduced Ni 0 ion in the oxidative addition step . Moreover, the little more electronegativity of Ni 2+ ion compared to that Co 2+ ion could improve the Ni‐Sanp catalytic potential due to the faster oxidative addition step achievement in the catalytic cycle more than that Co‐Sanp . The octahedral geometry of Co‐Sanp could discourage its catalytic potentials.…”

“…reported the synergistic influence of Co (II) ion on Pd (II)/Co (II) catalyzed Suzuki‐Miyaura cross coupling reaction in an aqueous media . N^O‐bidentate 2‐(hydroxyimino)‐1‐phenylpropan‐1‐one coordinated to Co (II) ion in an octahedral geometry as an effective catalyst for Sonogashira Hagihara cross coupling of electron‐rich and/or electron‐poor substituted aryl halides of with alkyne derivatives . Cobalt chloride catalyzed the cross coupling of 1,3‐dienes (additives) within homogeneous complexation, as reported elsewhere .…”

Cobalt‐Catalyzed Three‐Component Synthesis of Propargylamine Derivatives and Sonogashira Reaction: A Comparative Study between Co‐NPs and Co‐NHC@MWCNTs

“…The Sonogashira reaction was compared with available methods using cobalt catalyst in the literature; as we know a few reports are available; results are given in Table . In the first entry which used unrecyclable homogenous cobalt complex as catalyst, in spite of applying room temperature conditions, the reaction just proceeded in the presence of ethylene glycol (EG) as additive under visible light illumination . In other report (Table , entry 2), CuI and three‐phenyl phosphine was used as co‐catalyst and additive, respectively; however, the desired products was achieved poorly after long reaction time .…”

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

“…Chu et al developed an efficient and inexpensive procedure for the formation of carbon-carbon bonds. This protocol involves the visible light-assisted Sonogashira coupling of aryl bromides and terminal alkynes in the presence of the Co(C 9 H 9 NO 2 ) 3 complex as the catalyst (Scheme 34) [45]. This novel catalytic system provided 23 alkyne products in a substrate scope study Scheme 35: Possible mechanism for the visible light-assisted cobalt complex-catalyzed Sonogashira coupling.…”