Substituents attached to ring nitrogen atoms

12 Substituents Attached to Ring Nitrogen Atoms 3.2.3.12.1 Introduction 

Substituents attached to a nitrogen atom in a six-membered heteroaromatic ring are to be found in compounds of the following types  

Significantly, types (b), (c) and (d) can all be derived from a compound of type (a) by deprotonation. 

We will survey the reactions of N-linked substituents classified by the atom attached to the cyclic nitrogen. Unlike heterocyclic C-substituents, where the benzene prototype and the carbonyl analogy link much of the typical chemical behavior to familiar compounds, no simple model exists for N-substituents. However, certain trends are clear. The existence of the positive pole in cations of type (922) ensures that nucleophilic attacks (a)-(d) are the most important of the following reaction types, many of which occur for several of the different classes of N-substituents. 

Transfer of an A-alkyl group to certain nucleophiles can also occur by a radicaloid non-chain mechanism, e.g. (935 R = CH2Ph, R = Ph) + CMe2N02 — (937) — (938) + (939). 

The oxygen of 1,2-benzisoxazole A-oxides can be removed by treatment with triethyl phosphite (80CC421), and the oxygen of 3,4,5-triphenylisoxazoline A-oxide with H2 catalysis and PCI5 (69JOC984). Isoxazoline A-oxide (272) reacts with styrene to give cycloadduct (273) (66ZOR2225). 

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Reactivity of Substituents Attached to Ring Nitrogen Atom. 252... 

Reactivity of substituents attached to ring nitrogen atom 105... 

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