Nucleophilic aliphatic ambident nucleophiles

Nucleophilic substitution, aliphatic, 31, 45, 77-100 Ag catalysis, 97 allyl halides, 85 ambident nucleophiles, 97 benzyl halides, 84, 91 bridgehead halides, 86 bromomethane, 78 2-bromopropanoate, 94 1-bromotriptycene, 87 carbanions in, 100,288... 

Lately some investigations have been conducted regarding the reaction of the ambident nucleophile phenylhydrazine with DMC. Phenylhy-drazine contains two non-equivalent nitrogen nucleophilic centres. N-1 is relatively more acidic due to the electron withdrawing effect of the phenyl ring substituent while N-2 possesses reactivity similar to that of an aliphatic amine. 

The demonstration of ambident nucleophilic reactivity of aryl oxides in their reactions with nitroaromatics raises the question whether aromatic amines might function similarly. However, TNB does not react with aniline alone to form a stable a complex only a charge transfer or tt complex is formed (33). This result is perhaps surprising because TNB is well-known to form stable a complexes with primary or secondary aliphatic amines (7, 8). 

Another attempt to use the host-guest complexation of simple cyclophanes has been reported by Schneider They take the easily accessible host 7, an analogue of which had been demonstrated by Koga to bind aromatic guest molecules by inclusion into its molecular cavity, and study its rate effects on nucleophilic aliphatic substitutions of ambident anions (NOf, CN, SCN ) on 2-bromomethylnaphthalene 8 and benzylbromide. Similar bimolecular reactions are well known in cyclodextrin chemistry and other artificial host systems . In addition to the rather poor accelerations observed (see Table 3) the product ratio is changed in the case of nitrite favouring attack of the ambident nucleophile via its nitrogen atom. 

A mechanism of this type permits substitution of certain aromatic and aliphatic nitro compounds by a variety of nucleophiles. These reactions were discovered as the result of efforts to explain the mechanistic basis for high-yield carbon alkylation of the 2-nitropropane anion by / -nitrobenzyl chloride. -Nitrobenzyl bromide and iodide and benzyl hahdes that do not contain a nitro substituent give mainly the unstable oxygen alkylation product with this ambident anion ... 

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