Nitrogen-Carbon Couplings

In these reactions, the nitrogen nucleophile is typically an amide, carbamate, or sulfonamide. Because of the low nucleophilicity of such nitrogen functions, no intermolecular 1,4-addition involving C—N bond formation is known. In all cases reported, the carbon-nitrogen coupling takes place in an intramolecular aminopalladation. 

After having discussed catalytic reactions involving carbon monoxide, hydrogen, carbon monoxide and hydrogen, as well as carbon monoxide and water, this section is dedicated mainly to isomerization and rearrangement reactions and to carbon-carbon and carbon-nitrogen coupling reactions. 

One-bond carbon-nitrogen couplings, Dcn of ca. 3 Hz have been measured by Kelemen et aU for a series of labelled alkoxyamines, the model compounds for nitroxide-trapping studies in free radical copolymerization. Absolute Dcn values have been obtained for some mesoionic compounds and related structures by Jazwinski and Staszewska-Krajewska. " ... 

Ansatz (43) is the basis for many empirical findings, such as the observations that one-bond carbon-hydrogen couplings /( CH) are related to the hybridizations of the corresponding carbon atoms (61) or that carbon-carbon couplings y( 3C C) parallel the product sc-sc of the hybridizations of the carbon atoms (62) or that sometimes carbon-nitrogen couplings may be related to the hybridizations sc Sm (63). 

The situation for carbon-nitrogen couplings is complicated (636). Concerning one-bond carbon-nitrogen couplings it has been suggested that the Fermi contact term is dominant for all CN systems for which isosteric CC systems exist (156). In particular, in most CN systems with formal lone-pairs apart from the Fermi contact term the orbital and spin dipolar terms are operative and non-negligible (636,156). 

One-bond carbon-nitrogen coupling 438-439, Two-bond carbon-nitrogen coupling 441,... 

The only side-product observed was the arene resulting from reduction of the starting aryl chloride. This is in fact the first example of carbon-nitrogen couplings mediated by nickel dihydroimidazolidine carbene complexes. 

Kogan, V., Aizenshtat, Z., Popovitz-Biro, R., et al. (2002). Carbon-Carbon and Carbon-Nitrogen Coupling Reactions Catalyzed by Palladium Nanoparticles Derived from a Palladium Substituted Keggin-Type Polyoxometalate, Org. Lett., 4, pp. 3529-3532. 

The ingenious undemanding Hartwig-Buchwald palladium-catalyzed carbon-nitrogen coupling can also be favorably used for the synthesis of benzotriazoles (332). This way, both the amine and the arylhalide can be immobilized. Crucial for the success is the careful choice of the ligand used (Scheme 47). 

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