Copper-mediated reactions arylboronic acids

B. Copper-mediated Reactions of Arylboronic Acids with Amines. 510... 

Copper-mediated reactions of arylboronic acids with aromatic and... 

While a considerable amount of effort has been devoted to developing copper-mediated reactions that mimic palladium-catalyzed processes due to the reduced cost of copper versus palladium, their reactivity can be markedly different in certain reactions and give rise to a different product distribution. Such a difference has been observed in the reaction of carboxylic acids with arylboronic acids [99]. When palladium catalysts were... 

Bromo- and iodoimidazoles are useful intermediates for further functionalization. 4(5)-Aryl- I //-imidazoles 57 can be efficiently and selectively prepared by palladium-catalyzed Suzuki-Miyaura reaction of commercially available 4(5)-bromo-l//-imidazole 56 with arylboronic acids under phase-transfer conditions, which then underwent highly selective palladium-catalyzed and copper(I) iodide mediated direct C-2-arylation with a variety of aryl bromides and iodides under base-free and ligandless conditions to produce 2,4(5)-diaryl-l//-imidazoles 58 in modest to good yields <07JOC8543>. A new procedure for the synthesis of a series of substituted 2-phenylhistamines 60 utilizing a microwave-promoted Suzuki... 

In addition to aliphatic and aromatic amines, amides275 and sulfonamides285 have also been used as nitrogen nucleophiles for copper-mediated coupling with arylboronic acids, and these reactions provide protected anilines. 

Reports by the groups of Chan, Evans, and Lam in 1998 revealed an alternative method to conduct copper-mediated couplings that form C(aryl)-0 and C(aryl)-N bonds. In this process, arylboronic acids react with compounds containing N-H or 0-H bonds in the presence of a Cu(II) reagent or catalyst. TTiese reactions were initially conducted with stoichiometric amounts of copper reagents. " Amines, anilines, amides, ureas, carbamates, and sulfonamides underwent N-arylation in moderate to excellent yields by this process (Equation 19.124). The commercial availability of boronic acids and the ability to conduct these arylations in air under mild conditions has caused this method to be adopted quickly for synthetic applications on a small scale. 

Kelly and co-workers have shown that N-hydroxyphthalimide undergoes copper-mediated cross-coupling with a diverse set of arylboronic acids to give the corresponding 0-arylated products in reasonable yields. Pyridine turned out to be the best amine base for this reaction - better than EtjN, 4-dimethylaminopyridine (DMAP), CS2CO3, and DABCO. Interestingly, of all the copper salts screened, Cu(i)Cl and... 

Abstract This review covers the recent recyclable protocols for the C-N bond forming reactions between aromatic, heterocyclic and aliphatic amines such as imidazoles, benzimidazoles, benzylamines, piperidine, pyrrole, imides, anilines, hexyl, cyclohexyl amines, and amides as coupling partners with aryl iodides, bromides, chlorides, and arylboronic acids employing copper-mediated systems. The physical properties and characterization of the catalysts and their use in organic synthesis will be outlined. Most importantly, these recyclable versions developed by many groups in the recent years are potential candidates for commercial exploitation. The effect of additives, solvents, temperature, base, the nature of aryl halides on reactivity, and recycle studies of the heterogeneous catalysts are included in this... 

Copper acetate, triethylamine-mediated CN cross-coupling reaction of arylboronic acids at room temperature to solid-supported primary and secondary amines gave good to excellent yields of the desired Ai-arylated products [78]. This method demonstrates the generality of this methodology for the solid-phase synthesis of combinatorial libraries (Scheme 17). 

AU these authors proposed that the mechanism bears some similarity to the copper-mediated arylation of amines from triarylbismuth compounds, described by Barton et al. [273]. Thus, the reaction would proceed via the formation of a cupric acetate complex with the nucleophile followed by a transmetallatimi with arylboronic acid playing the role of the triarylbismuth, before affording the N-arylated compound by reductive elimination. This last step would be facilitated by prior oxidation by dioxygene of a copper II intermediate to a copper IB intermediate [266-270, 274]. Some authors reported that the addition of molecular... 

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