Chan-Lam reaction

Evans describes the possibility of a common intermediate for the Ullman and Chan-Lam reactions. D. A. Evans, J. Katz, T. R. West, Tetrahedron Letters 1998, 39, 2937... 

This chapter covers more specifically the copper-catalyzed C(aryl)-N bond formation via the coupling of aryl halides with nitrogen nucleophiles such as N-heterocycles, amines, anilines, amides, ammonia, azides, hydroxylamines, nitrite salts or phosphonic amides. The C(aryl)-N bond formation as a result of the coupling between these nucleophiles and arylboronic acids (the Chan-Lam reaction) will be also presented. It is worth noting that this chapter mainly focuses on the most significant results and important breakthroughs in this field. 

Recently, the Chan-Lam reaction was also adapted for the synthesis of aniline derivatives. Indeed, in 2009, Fu et al. described the base- and Ugand-free copper-catalyzed coupling of arylboronic acids with aqueous ammonia (Scheme 30) [234]. This very simple system used 10% of CuzO under air at room temperature and affords the corresponding aniline derivatives in very good yields. The reaction can also be carried out from arylboronic acid esters. A related reaction, performed in water with CUSO4.5H2O as catalyst, was more recently reported by Wu [235]. Fu et al. also reported a quite similar system [236]. 

Since a decade, impressive progressions have been accomplished for the copper-catalyzed formation of C(sp )-N bonds. Both Ullmann and Chan-Lam reactions have permitted the coupling of a wide array of nitrogen nucleophiles with aryl/vinyl halides and boronic acids, respectively. The simplicity of the ligands, when necessary, their commercial availability and the low cost of copper make these reactions very attractive compared to palladium cross coupling, though the latter are considered complementary one to another. 

Scheme 5.4 Chan-Lam coupling reactions and a simplified catalytic cycle.

Liebeskind reported a copper-catalyzed Chan-Lam C-N crosscoupling methodology for JV-imination of boronic acids by using oxime O-carboxylates 291 as iminating agents and either Cu(I)-thiophene-2-carboxylate (CuTC) or Cu(OAc)2 as the catalyst under nonbasic and nonoxidizing conditions.Subsequently, the A-alkenylated a,3-unsaturated ketoxime 0-pentafluorobenzoates 293, were preeursors in a cascade reaction for the one-pot synthesis of tri-, tetra-, and penta-substituted pyridines 295 in moderate to excellent isolated yields. 

Arylation of a wide range of NH/OH/SH substrates by oxidative cross-coupling with boronic acids in the presence of catalytic cupric acetate and either triethyl-amine or pyridine at room temperature in air. The reaction works for amides, amines, anilines, azides, hydantoins, hydrazines, imides, imines, nitroso, pyrazi-nones, pyridones, purines, pyrimidines, sulfonamides, sulfinates, sulfoximines, ureas, alcohols, phenols, and thiols. It is also the mildest method for NIO-vinylation. The boronic acids can be replaced with siloxanes or starmanes. The mild condition of this reaction is an advantage over Buchwald-Hartwig s Pd-catalyzed cross-coupling. The Chan-Lam C-X bond cross-coupling reaction is complementary to Suzuki-Miyaura s C-C bond cross-coupling reaction. 

Chan—Lam couphng reactions Synthesis of heterocycles 12T7735. Chemistry of propargyl compounds activated by sulfur functional groups Development of methodology for the synthesis of heterocycles triggered by functionalizations 13YGK1282. 

Oxidative Cross-Coupling (Chan-Evans-Lam Reaction) The coupling of phenols with aryl boronic acids has been accomplished (Scheme 20.37). Initially, Chan and coworkers studied an equivalent amount of CulOAc) for the coupling reaction [58]. Subsequently, Evans and coworkers found the use of MS 4 A led to improvement in the yield of the target product [106]. Later, Lam and coworkers made the process catalytic using oxygen as an oxidant [107]. Their mechanistic aspects have been recently demonstrated [108]. 

SCHEME 20.37 Chan-Evans-Lam reaction oxidative cross-coupling. 

Copper has also found wide use however, it has generally only been found to be applicable to heteroatom-carbon coupling reactions when employing boronic acids as coupling partners, now known as the Chan-Lam coupling. ... 

Scheme 2.19 Putative general mechanism for the Chan-Lam-Evans arylation reaction [12d, 98].

Bruneau et al. [102] showed that it was also possible to conduct this reaction with glucosamines. Pentacetylated aminoglucose and other derivatives could be successfully arylated under Chan-Lam-Evans catalytic conditions (Figure 2.22). The yields were good. 

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