Reactions of amino compounds with nucleophiles

Three modes of reaction are possible proton loss, nucleophilic displacement and Dimroth rearrangement. 

Nucleophilic reagents can also react with 2- and 4-aminopyridines at the carbon atom which carries the amino group in a replacement reaction (e.g. 738 — 739) similar to, but far less facile than, that undergone by chloro and alkoxy compounds, etc. In this way aminopyrimidines can be converted into pyrimidinones by direct acidic or alkaline hydrolysis under rather vigorous conditions. 

Reactions of this type are easy if the amino group is quatemized as in, for example, l-(4 -pyridyl)pyridinium chloride (740), which gives pyridine and 4-substituted pyridines [741 Nu = Cl, Br (with PX5), Nu = SH, SR (with SH , SR-), Nu = NH2, NHR (withNH3, NH2R)]. Similarly, NMe3+ groups in pyrimidines undergo nucleophilic displacement. 

Dimroth rearrangement of neutral heterocyclic bases is also possible. For example, 1-ethyladenine heated in NaOH produces N(6)-ethyladenine (91%), hypoxanthine (2%) and 1-ethylhypoxanthine 

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Reactions of amino compounds with nucleophiles and bases 347... 

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