Aryl halides copper-catalyzed coupling

There are many other transition-metal catalyzed coupling reactions that are based on organic halides in aqueous media. One example is the coupling of terminal alkyne with aryl halides, the Sonogashira coupling, which has been discussed in detail in the chapter on alkynes (Chapter 4). An example is the condensation of 2-propynyl or allyl halides with simple acetylenes in the presence of copper salts. 

Okuro, K., Furuune, M., Miura, M., Nomura, M. Copper-catalyzed coupling reaction of aryl and vinyl halides with terminal alkynes. 

Ma and coworkers242 noticed the accelerating effect of a-amino acids in the copper-catalyzed coupling reactions of aryl halides with a-amino acids using Cul as catalyst and K2CO3 as base. The authors noted that the coupling reaction of bromobenzene with L-... 

Interest in copper-catalyzed coupling reactions has resurged due to the economic attractiveness of copper. Two different groups described the use of copper as a catalyst for efficient arylation reactions. Cristau and Taillefer detailed a mild copper-catalyzed N- and C-arylation with aryl bromides and iodides with various substrates <04CEJ5607>. One reaction examined was A -arylation of 2-pyridones. Li et al. has explored the copper-catalyzed coupling reaction of 2-pyridones 27 with aromatic halides 28 based on Buchwald s protocol to prepare N-aryl-2-pyridones 29 <04TL4257> as shown in Scheme 12. 

Although thiols are generally stronger nucleophiles than alcohols and amines, the sensitivity of sulfides towards oxidation as well as the formation of disulfide made the cross-coupling between aryl halides and thiols difficult. From all previously reported results, it was foimd that only aryl iodides were suitable for this copper-catalyzed coupling process. 

Copper-catalyzed couplings of phenols with aryl halides. 2-(3 ,4 -Dimethyl-phenoxy)benzoic acid ... 

Copper-Catalyzed Coupling of Amides with Aryl Halides... 

Copper-Catalyzed Coupling of Aryl Halides with Alcohols and Thiols... 

CO insertion prior to the transmetallation step. The mechanism of nickel-catalyzed coupling reactions is less established. Early studies indicated that homocoupling processes occur by oxidative addition through radical intermediates and possible intermediacy of Ni(I) and Ni(III) complexes. The copper-catalyzed cross-coupling reactions likely occur by transmetallation prior to oxidiative addition of the aryl halide. Iron-catalyzed reactions likely occur by low-valent, even sub-valent, species. 

Some of the advantages of copper catalysts are that they are inexpensive, abundant etc. In 2013, Fu, Peters and their co-workers reported a copper-catalyzed coupling of aryl halides with thiols via a single-electron transfer pathway. In order to prove the reaction mechanism, they performed the reaction of allyl-o-iodophenol with thiophenol as well. No cyclized product could be produced when the reactions were performed in the dark, while 57% of dihydrobenzofuran was formed when hv was introduced (Scheme 2.40). 

If there are no other electrophiles present in the compound, treatment of a chlorophosphine with a Grignard/ oiganolithium reagent has been an effective strategy [265]. Additionally, a copper-catalyzed coupling reaction has successfully used bulky aryl halides [24]... 

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