Synthesis Of3,4-Propyldioxythiophene-Tetrathiafulvalene Assemblies

Tetrathiafulvalene and thiophene derivates have attracted widespread attentions due to their excellence photoelectrochemical properties. We herein designed and synthesized two units. TTF3and3-Methyl-3,4-dihydro-2H-thieno[3,4-b][l,4]dioxepin-3-o1TP2. TTF3and TP2are functioned with carboxyl and hydroxyl groups, respectively.The work of preparation of TP2was underwent toughly. At the begining. we used2.5-diethoxycarboxy-3,4-dimethoxythiophene and1,1,1-trimethylolethane as raw materials to directly synthesis of3,4-propylenedioxythiophene derivate TP1via Mitsunobu reaction. However, this synthetic route was abandoned due to difficult to purify and low yield. After several trials, we used2,5-diethoxycarboxy-3,4-dimethoxytiophene as intermediate, then transformed it to3,4-dimethoxythiophene via saponificatin and decarboxylation.3.4-Dimethoxythiophene reacted with1,1,1-trimethylolethane to afford3-Methyl-3.4-dihydro-2H-thieno[3,4-b][l,4]dioxepin-3-o1. Influence of different reagents, solvents and the conditions to the methylation, decarboxylation and etherification reaction were investigated as well.TTF3was prepared by cross-coupling ketone and dithione to form asymmetrical TTF1. which could react with ethyl bromoacetate to afford TTF2in the presence of caesium hydroxide. Our objective TTF unit TTF3was finally obtained by reacting TTF2with lithium hydroxide.3.4-Propyldioxythiophene-tetrathiafulvalene assemblies was obtained by Steglich esterification of TTF3with TP2. Its UV-Vis spectra and cyclic voltammetry (CV) indicated weak intramolecular interactions between TTF and TP units.