N-Heterocyclic compounds

Stereocontrolled Additions to Dihydropyridines and Tetrahydropyridines Access to N-Heterocyclic Compounds Related to Natural Products... 

The availability of aniline has made possible a direct study of the reactions of aniline with humic and fulvic acids (Thom et al. 1996), and the detection of resonances attributed to anilinoquinone, imines, and N-heterocyclic compounds are fully consistent with reactions involving quinone and ketone groups. 

N-heterocyclic compounds containing six-membered rings (pyridine and analogues) behave as excellent -acceptors and in turn they provide a rather soft site for metal ion coordination. The 7r-excessive five-membered pyrazole is a poorer 7r-acceptor and a better 7r-donor and it acts as relatively hard donor site. Inclusion of six- and five-membered N-heterocycles like pyridine and pyrazole in one ligand system leads to very attractive coordination chemistry with variations of the electronic properties.555 The insertion of a spacer (e.g., methylene groups) between two heterocycles, which breaks any electronic communication, makes the coordination properties even more manifold. 

Table 14 shows a compilation of the N-heterocyclic compounds present in oil-derived fuels. The boiling point values and their MW have been included to indicate the fraction in which they will most likely be present. 

The cyclizahon of amino alcohols should be an attractive method for the synthesis of N-heterocyclic compounds, mainly because they can be obtained in a single step and without the generation of wasteful byproducts. Carbon-nitrogen bond formation catalyzed by Cp lr complexes has been extended to the synthesis of N-hetero-cyclic compounds by the cyclization of amino alcohols. 

Kita et al. found that phenolic oxidative coupling in case of 272 provides seven-membered N heterocyclic compounds 274 and 275 by bond shift of the initially formed spiro intermediate 273 under suitable conditions. Besides 274 and 275, piperidino-spiroquinone 276 is also formed in this oxidation (Scheme 68). Of particular interest is the recently developed synthesis of amaryllidaceae alkaloids such as (+)-maritidine (Scheme 69) (96JOC5857). 

Sec. III.A] ELECTROLYSIS OF N-HETEROCYCLIC COMPOUNDS 4. Formation of Nitrogen-Nitrogen Bonds... 

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