Carbon-nitrogen bond formation 3-amination

The preparation of amines by the methods described m this section involves the prior synthesis and isolation of some reducible material that has a carbon-nitrogen bond an azide a nitrile a nitro substituted arene or an amide The following section describes a method that combines the two steps of carbon-nitrogen bond formation and reduction into a single operation Like the reduction of amides it offers the possibility of prepar mg primary secondary or tertiary amines by proper choice of starting materials... 

Transition metal complex-catalyzed carbon-nitrogen bond formations have been developed as fundamentally important reactions. This chapter highlights the allylic amination and its asymmetric version as well as all other possible aminations such as crosscoupling reactions, oxidative addition-/3-elimination, and hydroamination, except for nitrene reactions. This chapter has been organized according to the different types of reactions and references to literature from 1993 to 2004 have been used. 

An important variant for transition metal-catalyzed carbon-nitrogen bond formation is allylic substitution (for reviews, see1,la lh). Nucleophilic attack by an amine on an 7r-allyl intermediate, generated from either an allylic alcohol derivative,2 16,16a 16f an alkenyloxirane,17-19,19a-19d an alkenylaziridine19,19a 19d, or a propargyl alcohol derivative,21,21a 21d gives an allylic amine derivative. 

Carbon-Nitrogen Bond Formation Based on Hydrogen Transfer 129 Table 5.11 N-Heterocyclization of primary amines with a variety of diols by [Cp lrCl2]2 (1) ... 

Carbon-nitrogen bond formation, by reductive amination, 59, 1 Carbon-phosphorus bond formation, 36, 2 Carbonyl compounds, addition of... 

Not only acetylene derivatives do undergo palladium catalysed intarmolecular carbon-nitrogen bond formation with amines. The similar reaction of olefins in a Wacker-type process also leads to ring closure. (0-Aminopentenes bearing a suitable leaving group in the 4-position were converted to pyrroles in a cyclization-isomerisation-elimination sequence (3.65.),82... 

In certain cases, when the palladium or nickel catalyzed coupling is not efficient or fails completely, an alternate solution is provided by the use of copper based catalyst systems. The 5-iodouracil derivative shown in 7.77. was unreactive towards imidazole using either the Buchwald-Hartwig conditions or the copper(I) triflate promoted the carbon-nitrogen bond formation reported by Buchwald98 These latter conditions, however, were effective in coupling the iodouracil with a series of other amines (7.77.), The optimal catalyst system consisted of copper(I) triflate, phenantroline and dibenzylideneacetone (dba).99... 

As an alternative to primary amines in these double carbon-nitrogen bond forming reactions, Maes has demonstrated that 22 can undergo consecutive palladium-catalyzed carbon-nitrogen bond formation with orfho-dihalopyridine derivatives (Scheme 6.42). This reaction proceeds in good yield with a number of amidine variants, and provides a route to the construction of polycyclic imidazoles [54]. 

Carbon-nitrogen bond formation is an important subject in the organic synthesis [301], and hydroamination is an atom-efficient process for the generation of amines and imines from olefins, allenes, and alkynes. Titanium-mediated hydroamination was among the most useful protocols thus far developed for this reaction. By using unsymmetrical olefins and alkynes, the addition of HNR2 can in principle lead to two isomeric products, where the isomeric ratio is usually dependent on the type of titanium catalyst used. 

The large slopes (a = 0.7-1.0) indicate a very strong dependence of kx on amine basicity, and considerable carbon-nitrogen bond formation in the transition states. These results suggest a hard character for the dienyl rings in cations 20 (M = Fe) and 25. 

OxidativeN-Arylation. Cu(OAc)2 has been shown to facilitate synthetically useful oxidative formation of carbon-nitrogen bonds. The amination of various boronic acids, pioneered by Lam et al. has been employed as a mild alternative to aromatic amination of aryl halides. Various aryl and vinylboronic compounds were aminated in presence of a base and either a stoichiometric or a catalytic amount of Cu(OAc)2 in latter case with air as the oxidant and myristic acid as a co-catalyst (eq 22). Dichloromethane or toluene were the solvents of choice. The influence of various oxidants and co-oxidants on the reaction process was also examined. ... 

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