Two Nitrogen Atoms

Diaziridines, formation in reactions of carbenes with azo compounds 87UK1324. 

Compound (126) can also be obtained by irradiation of (127). Treatment of either (124) or (125) with sodium methoxide in methanol affords a third tautomer, viz. (128), from which the 3,4-dihydro-5 f-2,3-benzodiazepine (129) 

The cation of 3,5,7-triphenyI-4JT-l,2-diazepine (141) was originally considered to have structure (142), but n.m.r. and X-ray diffraction studies of the picrate now indicate that this structure should be discarded in favour of (143) or (144). The cation exists in a boat conformation and the free energy of activation for the inversion process is substantially lower than that for the unprotonated ring, possibly because of the absence of lone-pair-lone-pair 

Photolyses of H- and 5-/T-2,3-benzodiazepines provide an interesting comparison. The former series (147) gives the ring-collapsed products (148), 

Acylation of the diazepinol (156) in the presence of a weak base gives the bicyclic compound (158), probably via the cation (157). However, in the presence of strong base, the six-membered ring structure (160) is formed, presumably via the betaine (159). In the diazepinone series, methylation of (161) 

Two Nitrogen Attnns (1 ).—The use of bicyclic amidines (168), particularly as dehydrohalogenating agents, has been reviewed.  

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The hemicyanines constitute a particular class among streptocyanines in which one of the two nitrogen atoms belongs to a heterocycloammonium. Thiazolohemicyanine corresponds to the general formula in Scheme 31. When R = R, = H. the dyes are of aminovinyl type when R = H. R3 = Ph. they are aniiinovinyl compounds, and when (-CH=CH) is replaced by a benzene ring, they are aminophenyl. 

The bonding in the mononuclear metal complexes is considered to involve the two nitrogen atoms of the ligand structure, giving the familiar... 

EthylenediaminetetraaceticAcid. Ethylenediaminetetraacetic acid (EDTAH has six potential donor groups two nitrogen atoms and four carboxylate groups. If EDTA 4— acts as a hexadentate ligand to a metal, the resulting complex contains five five-membered chelate rings and has a charge that is four less than that of the metal ion. 

When two fused six-membered rings (naphthalene analogues) are considered, possibilities become very numerous, partly on account of the reduced symmetry of naphthalene, compared with benzene, and also because of the larger number of positions available for substitution. Thus, there are two monoazanaphthalenes, quinoline (8) and isoquinoline (9), four benzodiazines [cinnoline (10), phthalazine (11), quinazoline (12) and quinoxaline(13)], with the two nitrogen atoms in the same ring, and six naphthyridines (e.g. (14), named and... 

The fully saturated pyrazolidines have been utilized as models for the study of the nitrogen inversion of hydrazines. For instance, (75), a 2,3-diazabicyclo[2.2.1]heptene derivative, presents a consecutive inversion process at two nitrogen atoms with an activation barrier... 

Substitution with conservation of the three-membered ring is more versatile in diaziridine chemistry, because the ring is somewhat more stable and because of the presence of two nitrogen atoms. 

As a substance of formula (HI) should lose carbon dioxide on heating, whereas pilopic acid is stable even at 200°, it seemed probable that homo-pilopic acid is represented by (II) and pilopic acid by (IV). Jowett also showed that pilocarpine, like wopilocarpine, yields Aomopilopic acid when oxidised by permanganate.In the oxidation of the two alkaloids the two nitrogen atoms are eliminated as ammonia and methylamine. 

Histidine is one of the 20 naturally occurring amino acids commonly found in proteins (see Chapter 4). It possesses as part of its structure an imidazole group, a five-membered heterocyclic ring possessing two nitrogen atoms. The pAl for dissociation of the imidazole hydrogen of histidine is 6.04. 

Peganine has two nitrogen atoms and its monoacidity is due to the formation of a cyclic amidinium cation. The Schopf-Oechler scheme for the synthesis of peganine from o-aminobenzaldehyde and... 

The 5H-imidazole ring (37) possesses two nitrogen atoms with lone pairs e,vailable for quaternary salt formation, but unlike those in the... 

Such modifications can be produced either in the kinetic aspects (proton transfer) or in the equilibrium constant. Both effects are mediated by intramolecular hydrogen bonds. For instance, Navarro et al. (93MI69) showed that the rate of proton transfer between the two nitrogen atoms of pyrazole (annular tautomerism) is considerably reduced in macrocycles containing oxygen or nitrogen atoms in the macroring. 

Six-membered heterocycles with one tellurium and two nitrogen atoms in the ring are represented by 2-aroyl derivatives of 1,2,3-telluradiazine and 5,6-benzo-1,2,3-telluradiazine 89. For the synthesis of these compounds, IV-aroylhydrazones of 2-bromotellurenylcyclohexenealdehyde and 2-bromotellurenylbenzaldehyde 90 were used as the starting materials (98ZOK959). Dehydrobromination of the hydrazones 90 occurs on treatment with triethylamine and gives the heterocycles 89 in about 80% yields. 

Two Nitrogen Atoms and One Sulfur Atom. s -Triazolo[3,4-d]-l,3,4-thiadiazole derivatives 98Ft(48)561. 

Two Nitrogen Atoms and One Oxygen Atom Synthesis of 1,3,4-oxadiazines 98H(49)557. 

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