Alkyl halides reactions with ambident

Treatment of alkyl halides with alkali metal or silver cyanate is of no preparative value for the synthesis of cyanates. - - As cyanate ions do represent ambident nucleophiles. Holm and Wentrap tried to reach cyanates under well-defined SnI conditions (Scheme 28). But even treatment of isopropyl iodide with silver cyanate in nitromethane provided only a very low yield of a 1 1 mixture of isopropyl cyanate and the corresponding isocyanate, and from a reaction of silver cyanate with triphenylchloro-methane they isolated only triphenylmethyl isocyanate, although the cyanate may have been an intermediate in this transformation." ... 

The carbonyl tautomers deprotonate at N-H, generating ambident anions that can react at either oxygen or nitrogen, depending on the exact conditions for example 0-alkylation can be achieved with silver carbonate. They are converted, as with the pyridones, into halo-quinolines and halo-isoquinolines by reaction with phosphorus halides. 

Tertiary phosphines are rapidly quaternized by alkyl halides. During the reaction with the ambident triethoxycarbenium fluoroborate, phosphines seek the softer ethyl group (3). 

Phosphorothioate ions are also 0,S-ambident. Their reactions with alkyl halides and sulfenyl chlorides occur at the sulfur (25). 

Phenols can be viewed as stable forms of enol tautomers, and phenolate anions display ambident nucleophilicity at oxygen as weU as C2/C6 and C4 (ortholpara positions). Consequently, phenolate anions are susceptible to C—C bond formation upon reaction with appropriate organic electrophiles (e.g., alkyl halides and sulfonates). When bond formation occurs at a substituted arene carbon, a quatonaty centCT is generated, which may lead to isolation of stable cyclohexadienone products and complete a net alkylative dearomatization (Scheme 15.1) [2]. 

A mechanism of this type permits substitution of certain aromatic and ahphatic 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 p-nitrobenzyl chloride. p-Nitrobenzyl bromide and iodide and benzyl halides that do not contain a nitro substituent give mainly the unstable oxygen alkylation product with this ambident anion ... 

Hydroxamic acids undergo facile nucleophilic Ai-arylation with activated aryl halides such as 31 (equation 22). While hydroxamates are known to be ambident nucleophiles in alkylation reactions, arylation of hydroxylamines results exclusively in Ai-substituted hydroxamates of type 32 (equation 22)". ... 

Although it might be expected that reactions which employed triarylmethyl halides would occur very readily, such reactions are rendered potentially more complex by the known nature of the halides and their propensity for involvement in free radical reactions. Whereas normal alkylation proceeds between sodium diethyl phosphite and diphenyl-methyl halides, success, or otherwise, in the use of the triphenylmethyl halides depends to some extent on the individual halide and on the metal in the phosphite salt. Thus, in an early study (in 1939), Arbuzov found that in reactions between silver dialkyl phosphites and triphenylmethyl bromide, dialkyl triphenylmethylphosphonates were indeed formed, but the use of the corresponding alkyl chloride provided the phosphite triester instead (metal dialkyl phosphites possess ambident anions ). A later study confirmed the behaviour of the silver salts towards the chloride, but also showed that, whereas dialkyl phophites with primary alkyl groups yielded phosphonic diesters (as had already been found), those with secondary alkyl groups afforded phosphite triesters moreover, the presence and nature of aromatic substituents were also able to control the course of the reaction. Reactions which involve triarylmethyl halides and sodium dialkyl phosphites may well be of a free radical nature since repeated studies have demonstrated the forma-... 

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