Nucleophilic nitrogen atom

Other interesting regioselective reactions are carried out within the synthesis of nitrofurantoin. Benzaidehyde semicarbazone substitutes chlorine in chloroacetic ester with the most nucleophilic hydrazone nitrogen atom. Transamidation of the ester occurs with the di-protic outer nitrogen atom. Only one nucleophilic nitrogen atom remains in the cyclization product and reacts exclusively with carbonyl compounds. 

Figure 17.23 A traceless Staudinger ligation process involves the formation of an intermediate aza-ylide with subsequent attack of the nucleophilic nitrogen atom on the neighboring electrophilic group. The formation of an amide bond then occurs concomitant with the loss of the phosphine component, thus forming a zero-length crosslink between the two molecules.

Figure 11.9 Biuret reaction. The coordination complex formed in alkaline solution between cupric ions and the nucleophilic nitrogen atoms in four molecules of biuret.

Methyl tricyclo[4.1.0.0 ]heptane-l-carboxylate gives a cation-radical in which the spin density is almost completely localized on C-1 while the positive charge is on C-7. The revealed structural feature of the intermediate cation-radical fairly explains the regioselectivity of N,N-dichlorobenzenesulfonamide addition to the molecular precursor of this cation-radical. In the reaction mentioned, the nucleophilic nitrogen atom of the reactant adds to electrophilic C-7, and the chlorine radical attacks C-1 whose spin population is maximal (Zverev and Vasin 1998, 2000). 

Involvement of two nucleophilic nitrogen atoms is thus typical for the amino heterocycles. The mutual disposition of the pyridine and amine nitrogen atoms allows the formation of chelate structures for the cobalt complexes of purine, 221 and 222. Structures with the N, iV -five-membered metal cycles were proven for the tri- and tetranuclear complexes of silver ) with 8-aminoquinoline (223) (92IC4370), and polymeric copper- and rhodium-acetate clusters (224). Another coordination mode can be found in the complexes of 4-amino-3,5-bis(pyridin-2-yl)-l,2,4-triazole, (225 or... 

The type d ring closure to access monocyclic 1,4-diazepines is typically accomplished by uniting a nucleophilic nitrogen atom with an electrophilic carbon atom examples, where the latter is in either an spz or an sp3 hybridization state, have been described. 

Notice that it is the more nucleophilic nitrogen atom, and not the oxygen atom, of hydroxy-lamine that adds to the carbonyl group. Like hemiacetals, these intermediates are unstable and can decompose by loss of water. The product is known as an oxime and it is this compound, with its C=N double bond, that is responsible for the IR absorption at 1400 cm-1. 

By reaction of secondary V-arylketoenamines in the aminocyclopentenone series and quinones, the cyclopent[Z ]indole skeleton and dibenzo[6,d]cyclopent[/]azepines are accessible. The reaction involves an oxidative cyclization of the Michael adduct by attack of either the nucleophilic nitrogen atom or of the aromatic o-position of the aniline moiety on the quinone317 (equation 235). 

Polymerization of oxazolines is initiated by typical cationic initiators. Alkylation occurs on the more nucleophilic nitrogen atom (cf., however, Section II.A.5). Propagation may be visualized by the scheme ... 

To avoid polyalkylation, a nitrogen nucleophile is used that can react only in a single nucleophilic substitution reaction—that is, form a product that does not contain a nucleophilic nitrogen atom capable of reacting further. 

In the presence of acid, nitrous acid decomposes to " NO, the nitrosonium ion. This electrophile then goes on to react with the nucleophilic nitrogen atom of amines to form diazonium salts (RN2 Cr) from 1° amines and A -nitrosamines (R2NN=0) from 2° amines. 

Alcohols can be added to nitriles in an entirely different manner from that of reaction 16-9. In this reaction, the alcohol is converted by a strong acid to a carbo-cation, which is attacked by the nucleophilic nitrogen atom to give 117. Subsequent addition of water to the electrophilic carbon atom leads to the enol form of the amide (see 118), which tautomerizes (p. 98) to the V-alkyl amide. 

For nitrogen compounds where the nucleophilic nitrogen atom is hindered, the methyl cation affinity values calculated are less than those estimated by the reference model. The difference between the two values is assumed as the steric parameter, i.e ... 

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