A new synthesis of alkylsulphanylnaphthalenes and the synthesis and mesomorphic properties of novel naphthylisothiocyanates

The syntheses and transition temperatures of 2-(4-butylsulphanylphenyl)-6-isothiocyanatonaphthalene and 1-(4-butylsulphanylphenyl)-2-(6-isothiocyanato-2-naphthyl)ethyne are reported and discussed. These are the first examples of mesogenic isothiocyanatonaphthalenes to be reported in the literature. The transition temperatures of these compounds were compared and contrasted with compounds where the naphthalene and benzene rings had been interchanged and the analogous compounds where a cyano group replaced the isothiocyanate. The new compounds had high nematic phase thermal stabilities and relatively low melting points. As part of this work we present a new synthetic method for the synthesis of the key 2-alkylsulphanyl-6-bromonaphthalene building block that is a marked improvement over currently available methodology.