Carbon-nitrogen bond forming reactions reaction

Amines and amides undergo oxidation at or adjacent to nitrogen (Scheme 27). A neutral amine, for example, can be oxidized to afford a cation radical (117 to 116). Similarly, electrooxidation of the anion produced via deprotonation of a secondary amine leads to an aminyl radical (119) that is capable of participating in carbon-nitrogen bond-forming reactions with remotely tethered alkenes. 

Benzimidazoles bearing a halogen in the activated 2-position show a remarkable reactivity in palladium catalyzed carbon-nitrogen bond forming reactions. TV-protected 2-chlorobenzimidazoles reacted smoothly with a series of amines (6.81.). The activity of the aryl halide, besides the ready coupling of the chloro derivative, is also emphasized by the low catalyst loading used.112... 

Bipyridine was also en efficient ligand for the nickel-catalyzed carbon-nitrogen bond forming reactions. Using piperazine as a bifunctional amine, its monoarylation and diarylation were both achieved selectively with... 

Zwitterions in carbon-carbon and carbon-nitrogen bond-forming reactions as a promising synthetic strategy leading, in particular, to various heterocycles 06ACR520. 

Consecutive palladiumotalyzed carbon-nitrogen bond forming reactions can also be employed to access aromatic heterocycles. Nozaki has demonstrated this approach in the double N-arylation of 20 as a route to efficiently generate carbazoles (Scheme 6.40) [52]. This reaction can proceed with a range of alkyl and aryl amines, replacement of the aryl halides with sulfonates, and can even be performed consecutively to construct extended heteroacenes. 

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]. 

Palladium-catalyzed carbon-nitrogen bond forming reactions also provide an efficient route to generation of these precursors for Heck cyclization. Jorgensen... 

Carbon-Carbon and Carbon-Nitrogen Bond-Forming Reactions... 

Carbon - Nitrogen Bond Forming Reactions at Room Temperature... 

SCHEME 1.6 Example of an asymmetric palladium-catalyzed carbon-nitrogen bond-forming reaction [18]. 

Other examples of addition reactions that form carbon-nitrogen bonds are the reactions of hexafluoro-2-butyne with various heterocydes [77], aromatic... 

Scheme 3 shows the conceivable reaction sites of alkenylbismuthonium salts, alkynylbismuthonium salts, bismuth ylides, and bismuth imides in carbon-carbon and carbon-heteroatom bond forming reactions. In the initial step, nucleophiles (Nu) attack the positively charged bismuth(V) center, a-proton or (3-carbon (Scheme 3a, b) whereas electrophiles (El) attack the negatively charged a-carbon or a-nitrogen (Scheme 3c, d). Usually, the resulting bismuth(V) intermediates... 

Finally, a recently reported copper catalyzed carbon-nitrogen bond forming process utilises reagents with polarity opposite to the common disconnection protocols. An electrophilic nitrogen, in most cases an (9-acyl hydroxylamine derivative, was successfully coupled with diarylzinc reagents in the presence of copper triflate or copper chloride. Di(2 -pyridyl)zinc and TV-benzoyloxy-morpholine were reacted at ambient temperature in the presence of 1% copper(I) triflate to give 2-morpholinopyridine in 71% yield (7.81.), Under these mild conditions the reaction was over in less than one hour.103... 

The a-methoxylated derivatives are shown to be versatile synthons because of the reactivity of the methoxy group near the nitrogen atom, a-Methoxycarbamates, prepared by anodic oxidation, were used as key intermediates in the synthesis of a-amino acids,200 a new carbon-phosphorus bond-forming reaction,200 and in a new method of acylation of aliphatic amines at the -position.201 The application of this reaction to the synthesis of pyrrolidine, piperidine, and tropane alkaloids is also described.202... 

SYNTHESIS OF ALKYLAMINES AND RELATED COMPOUNDS THROUGH NITROGEN-CARBON(sp3) BOND-FORMING REACTIONS... 

The preparation of AJ-alkenyl nitrones has been achieved through the treatment of fluo-renone oxime with vinylboronic acids (Scheme 3.120) [126]. The nitrogen-carbon(sp ) bond-forming reaction was carried ont nnder mild conditions using copper acetate as the... 

Hydrogenolysis is analogous to hydrolysis and ammonolysis, which involve the cleavage of a bond induced by the action of water and ammonia, respectively. Chemical bonds that are broken by hydrogenolysis reactions include carbon—carbon, carbon—oxygen, carbon—sulfur, and carbon—nitrogen bonds. An example of hydrogenolysis is the hydrodealkylation of toluene to form benzene and methane ... 

The NAD- and NADP-dependent dehydrogenases catalyze at least six different types of reactions simple hydride transfer, deamination of an amino acid to form an a-keto acid, oxidation of /3-hydroxy acids followed by decarboxylation of the /3-keto acid intermediate, oxidation of aldehydes, reduction of isolated double bonds, and the oxidation of carbon-nitrogen bonds (as with dihydrofolate reductase). 

Reactions of this type are mostly performed with internal nucleophiles attached to the carbon atom adjacent to the iminium nitrogen, thus leading to tropane-like azabicyclic systems. Both allyl- and propargylsilanes, activated and unactivated alkenes, and ketones have been successfully used as nucleophiles. The products 1 and 2 are also obtained via two consecutive C —C bond-forming reactions in a single operation. 

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