C-N coupling process

Although the oxidative addition to form the arylpalladium-halide complex usually controls the rate of the C-N coupling process, the reactions of the arylpalladium-amido complexes tend to control the scope and yield. Studies on the reductive elimination of arylamines were presented in Chapter 8. This reaction may occur from a 14-electron, three-coordinate palladium species or a 16-electron, four-coordinate palladium species. If the palladium is ligated by a monodentate dative ligand, then the reaction occurs from the three-coordinate complex, but if the palladium is ligated by a bidentate dative ligand, then the reaction occurs from a four-coordinate complex. ... 

Nageswar et al. used nano-CuO for the efficient assembly of N-substituted indoles from indolines via the aromatization/C-N coupling process. No external ligand was... 

As already emphasized, the nature of the electrophile and the base are key factors in a C-N coupling process. In most cases, NaOtBu or KOtBu is the base of choice for the coupling of aryl halides or sulfonates. Substrates sensitive toward strong bases can be efficiently transformed if a milder base, such as CS2CO3, K3PO4 or even aqueous alkali hydroxide, is employed. The dialkyhnonophosphine Q-Phos (24) was employed in the coupHng of base-sensitive aryl halides such as chloro- and bromobenzonitriles and 4-chlorobenzoic acid ester (Scheme 13.34) [95]. 

Mechanisms of Metal-Mediated C-N Coupling Processes A Synergistic Relationship between Gas-Phase Experiments and Computational Chemistry... 

When [Fe(NH)] is reacted with benzene (0 = 70%), the major channel affords ionized aniline and also the other, two minor routes also indicate the operation of C-N coupling processes, Eq. (1.11). 

From L-tyrosine, or alternatively from L-phenylalanine, there is one further alkaloid biosynthesis pathway. This is the galanthamine pathway (Figure 38). Galanthamine synthesizes with tyramine, norbelladine, lycorine, crinine, N-demethylnarwedine and Al-demethylgalanthamine. Schiff base and reduction reaction, oxidative coupling and enzyme NADPH and SAM activity occur in this pathway. Schiff base is a reaction for the ehmination of water in formation with the C—N bonds process. 

For combination processes involving cyanoalkyl radicals, reversible C,N-coupling occurs in competition with C,C-coupling. Steric factors appear to be important in determining the relative amounts of C,C- and C,N-coupling and... 

In contrast to the synthetic approaches described in Sects. 3.2.1 and 3.2.2, the N-arylation and C-C coupling steps can also be reversed. Suzuki-Miyaura coupling of N-substituted 2-haloarylamines 189 with arylboronic acids 190 provides N-substituted 2-aminobiaryls 191 (Scheme 43). A palladium(II)-catalyzed oxidative cyclization of the latter forms the tricyclic carbazole framework. Different from the first reaction step in Scheme 24, this is an oxidative C-N coupling which requires N-H and C-H activation, whereas the C-C bond is formed in a crosscoupling process. 

Loiseleur and co-workers developed a process for the preparation of imatinib base, in which the final step involved a Pd2(dba)3CHCl3-catalyzed C-N coupling reaction with the of use of rac-BINAP as ligand. Others provided an improved process based on Loiseleur s method. However, the concerns of these approaches are the use of a toxic, hazardous reagent cyanamide and using relatively high-cost palladium as the catalyst for C-N coupling reaction. 

The application of inexpensive photoactive copper complexes has given great impulse to visible light-mediated photoredox catalysis, e.g. for C-C and C-N coupling reactions. Irradiation of Cu-complexes both triggers metal centred single electron transfer processes and assists the Cu-catalysed elemental steps, in which the substrate is covalently bonded. Successful extension of cooperative copper photocatalysis to other reactions is expected for the near future. " ... 

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