Preparation of Liquid Crystal Intermediates: 4-Substituted Alkoxybenzenes

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Abstract
Improvements in the O-alkylation of 4-substituted phenols with alkyl bromides in the presence of base by using anhydrous conditions has led to better methods for the preparation of 4-substituted alkoxybenzenes in which the substituent is either an aldehyde or a protected functional group. The protected groups can be benzyloxy, acetamido and carboxylic acid methyl ester which are easily converted to hydroxy, amino and acid chloride groups. A mixture of N,N-dimethylformamide and benzene containing molecular sieves and sodium hydroxide as the base along with an azeotropic distillation provides the necessary anhydrous conditions to avoid hydrolysis of the protecting groups. A variety of mesomorphic compounds such as 4,4′-disubstituted phenylbenzoates, phenylthiobenzoates, benzylideneamino (Schiff's bases) compounds and azoxybenzenes in which at least one of the terminal substituents is an alkoxy group can be prepared from these 4-substituted alkoxybenzenes.