Alpha-nitrogen

The heterocycle itself and the position of the nitrogen atoms within the ring. For example, in Table 1 we showed that a,0f-diphenylmethyl-3-pyridazine was inactive despite the presence of a beta positioned nitrogen. We supposed that the presence of the alpha nitrogen atom adjacent to the beta nitrogen was responsible for the lack of activity. 

Molecules of dimethylantimony azide are linked into infinite zig-zag chains, via the alpha nitrogen atoms and, if the antimony lone pair is stereochemically active, coordination about antimony is pseudo-trigonal bipyramidal with phenyl groups in equatorial positions and azide groups (Sb—N 2.32,2.43 A) in axial positions . The azide group is linear (178.5°) but the N—Sb—N angle (169.6°) deviates substantially from the 180° ideal the Sb—N—N angle is 117.4°. 

The third comparison of Interest is that of a one-bond-cleaving diazene with the corresponding N-oxide in which the oxygen is on the alpha nitrogen (eq. 6, k vs. kg). A desirable point of comparison would be triphenylmethylphenyldiazene N-oxide, j4. Several approaches to prepare this compound have been unsuccessful. An alternative was the methyl triphenylmethyldiazene-carboxylate, PhgCN2C02CH3, a diazene that decomposes into radicals at a rate close to that of phenyltriphenylmethyldiazene (21). Efforts to obtain the N-oxide of the triphenylmethyldiazene-carboxylate were also unsuccessful. Consequently, we sought to answer the question by examination of a benzhydryl system. 

Cross-linked PVP can also be obtained by cross-linking the preformed polymer chemically (with persulfates, hydrazine, or peroxides) or with actinic radiation (63). This approach requires a source of free radicals capable of hydrogen abstraction from one or another of the labile hydrogens attached alpha to the pyrrohdone carbonyl or lactam nitrogen. The subsequently formed PVP radical can combine with another such radical to form a cross-link or undergo side reactions such as scission or cyclization (64,65), thus ... 

Efforts to raise the alpha-selectivity have been made. Thus nitration of anthraquinone using nitrogen dioxide and ozone has been reported (17). l-Amino-4-bromoanthraquinone-2-sulfonic acid (bromamine acid) [116-81 -4] (8) is the most important intermediate for manufacturing reactive and acid dyes. Bromamine acid is manufactured from l-aminoanthraquinone-2-sulfonic acid [83-62-5] (19) by bromination in aqueous medium (18—20), or in concentrated sulfuric acid (21). l-Aminoanthraquinone-2-sulfonic acid is prepared from l-aminoanthraquinone by sulfonation in an inert, high boiling point organic solvent (22), or in oleum with sodium sulfate (23). 

Iodine isocyanate was used to synthesize the first steroidal aziridine, 2, 3 -iminocholestane (95). from 5a-cholest-2-ene (91). This reaction sequence which is believed to proceed through a three-membered ring iodonium ion (92) illustrates the limitation of pseudohalogen additions for the synthesis of -aziridines. The iodonium complex forms from the least hindered side (usually alpha) and is opened tmK5-diaxially to give a -oriented nitrogen function. The 3a-iodo-2 -isocyanate (93) is converted by treatment with... 

The oxidation of amines by mercuric acetate is an old reaction (54) which up until recent years was employed primarily to modify alkaloid structures (55). A systemic study of the oxidizing action of mercuric acetate by Leonard and co-workers led to the development of a general method for the synthesis of enamines from cyclic tertiary amines. An observation made after a large number of compounds were oxidized, but which is worth noting at the onset, is that a tertiary hydrogen alpha to the nitrogen atom is removed preferentially to a secondary a-hydrogen. 

The results observed in the oxidation of alkaloids which indicated something of the stereochemistry required for oxidation and prompted studies on model systems can now be interpreted more confidently. However, care must be used when basing steric differentiation on mercuric acetate oxidation studies since conditions must be employed which avoid epimerization at carbons alpha to the nitrogen. 

Goi. As noted previously, an a-chlorine atom renders a ring-nitrogen atom very weakly basic. Cyanuric chloride (5) is a very weak base both because s-triazines are of low basicity and because each of the ring-nitrogen atoms is alpha to two chlorine atoms. Hence, this compound should be insensitive to acid catalysis or acid autocatalysis and this has been observed for the displacement of the first chlorine atom with alcohols in alcohol-acetone solution and with water (see, however. Section II,D,2,6). 

Statements in the hterature on the reactivity of the ring-positions in monocyclic azines are conflicting. Reactivity is said to be greater at the position ortho (or alpha) than at the position para (or gamma) to an azine nitrogen 2-> 4-position in pyridine and pyrimidine and 3-> 5-position in as-triazine. By others, the... 

Proteins are also important nitrogen compounds. They constitute much of the cell materials, and are present in every type of organism known. In humans, muscle tissue, skin, and hair is mostly protein, about half of the dry weight of our bodies. From a chemical point of view, proteins are polymers of amino acids, alpha amine derivatives of carboxylic acids. Only about 20 different amino acids are actually found in proteins. It is the large number of variations in the protein chain, using only these... 

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