Synthesis of 5-n-alkylresorcinol dimethyl ethers and related compounds via substituted thiophens

Abstract

5-n-Alkylresorcinol dimethyl ethers have been synthesized by desulphurization of 2-(3,5-dimethoxybenzyl)-5-n-alkylthiophens with Raney nickel. The method has been adapted to the preparation of 9-(3,6- dimethoxyphenyl)nonyl alcohol which has been converted into both (2)- and (E)-15-(3,5-dimethoxyphenyl)pentadec-5-ene.     Friedel-Crafts acylation of 2-(3,5-dimethoxybenzyl)thiophen with n- hexoyl chloride, or with n-decoyl chloride, in the presence of stannic chloride, yielded the expected 2-(3,6-dimethoxybenzyl)-5-n- acylthiophens, but by-products were formed as the result of competing electrophilic attack on the 3,5-dimethoxybenzyl moiety. The chief by- products, which arise by subsequent Bradsher cyclodehydration, have been formulated as 5,7-dimethoxy-4-n-alkylnaphtho[2,3-b]thiophens.     An attempt to synthesize 1,14-bis(3,5-dimethoxyphenyl)tetradecane from 2,2?,6?,2?-terthienyl by an adaptation of this method was unsuccessful.