Alkylation of sodium 2-naphthoxide

The alkylation of sodium 2-naphthoxide with benzyl bromide in tetrabutylam-monium and tetrabutylphosphonium halide salts was investigated by Brunet and Badri [50] (Scheme 5.1-21). The yields in this reaction were quantitative, and alkylation occurred predominantly on the oxygen atom of the naphthoxide ion (typically 93-97 %). The rate of the reaction was slower in the chloride salts, due to the benzyl bromide reacting with chloride ion to give the less reactive benzyl chloride. 

The phase transfer method has also been used in the preparation of a variety of phenolic ethers [5]. It is interesting that alkylation of phenoxide anions generally yield products of both C and 0-alkylation with one favored to a greater or lesser extent depending on solvent. Sodium 2-naphthoxide, for example, exclusively C-benzylates in such hydrogen bonding solvents as ethanol [6], whereas 0-alkylation is favored in tetrahydrofuran. As the size of the cation associated with 2-naphthoxide is increased (for example from Li" to R4N ), 0-alkylation tends to be favored. Consistent with these observations is the report that 2-naphthol 0-alkylates under phase transfer conditions [5]. The successful 0-alkylation of the isomeric nitrophenols and salicyl-aldehyde are also noteworthy. These observations are consistent with the view that... 

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