Rings containing Two Nitrogen Atoms

The selected examples of six-membered heterocyclic rings containing two nitrogen atoms are based on the pyrimidine [(73), 1,3-diazabenzene], pyrazine [(74), 1,4-diazabenzene] and quinoxaline [(75), benzopyrazine] systems. 

Benzodiazepines are a series of compounds that have a benzene ring fused to a seven-membered ring containing two nitrogen atoms. The two most successful members of the group are diazepam (Valium ) and chlor-diazepoxide (Librium ) Flurazepam (Dalmane ) is a hypnotic. 

Even more complex is the stmcture of a hepatitis C protease inhibitor called BILN 2061, which has a 15-membered ring containing two nitrogen atoms (4.55). Olefin metathesis was used in the final step of its synthesis to close the ring of generalized intermediate 4.54 where several different R groups were used (Scheme 4.63). ... 

Benzodiazepine Glass of drugs that are structurally characterized by a seven-member ring containing two nitrogen atoms and that act as tranquilizers. 

The five-membered imidazole ring containing two nitrogen atoms is present in the naturally occurring amino acid, histidine. 

In pyrimidine there is a heterocyclic ring containing two nitrogen atoms. It is one of three isomeric diamines ... 

Compound 7 showed a UV maximum at 222 nm and disappearance of the aromatic protons observed at 8 8.67 in 1. Thus, the twelve heteroatoms present in 1 could be accounted for by 4 -OH, 2 -HNCO-, 2 -NH2 and 2-ArN and the six sites of unsaturation could be ascribed to two amide groups and one six membered aromatic ring containing two nitrogen atoms. 

In spite of the diverse nature of alkaloid structures, two structural units, i.e. fused pyrrolidine and piperidine rings in different oxidation states, appear as rather common denominators. We therefore chose to give several examples for four types of synthetic reactions which have frequently been used in alkaloid total synthesis and which provide generally useful routes to polycyclic compounds with five- or six-membered rings containing one nitrogen atom. These are ... 

Aromatic heterocycles containing two nitrogen atoms are best reduced by catalytic hydrogenation. Other reduction methods may cleave some of the rings. Even catalytic hydrogenation causes occasional hydrogenolysis. 

Pyrimidine is a six-membered aromatic heterocyclic compound that contains two nitrogen atoms, separated by a carbon atom, in the ring. Nucleic acids, DNA and RNA, contain substituted purines and pyrimidines. Cytosine, uracil, thymine and alloxan are just a few of the biologically significant modified pyrimidine compounds, the first three being the components of the nucleic acids. 

This chapter is concerned with all compounds having a three-mcmbered ring containing two carbon atoms and one nitrogen atom. The parent compound of this heterocyclic system is the unsaturated ring, which has two isomeric forme, I-azirine (1) and 2-azirine (IJ). Very few authentic examples of the azirines are known, and this review ib therefore concerned almost wholly with the chemistry of the saturated derivative, aziridine (111). 

Next, pirimicarb, a selective insecticide that kills sap-sucking aphid pests but does not affect the useful predators such as ladybirds (ladybugs) that eat them. It contains a pyrimidine ring—a benzene ring with two nitrogen atoms. 

Di-azo Compounds.—Contrasted with the azo compounds we have another group known as the di-azo compounds. As the name indicates these also contain two nitrogen atoms and these nitrogens are also directly linked to each other, but only one nitrogen atom is linked to a benzene ring. ... 

The imidazole ring in the histidine side chain contains two nitrogen atoms. Use SpartanView to compare energies and electrostatic potential maps of imidazolium ion A and imidazolium ion B. Which nitrogen of imidazole is more basic, and why ... 

---