Alkyl-Substituted PheDOT Derivatives and a PheDOT-Based Conjugated Dimer

3,4-Phenylenedioxythiophene (PheDOT) is an electron-rich heterocyclic building block that has attracted considerable interest for the preparation of conjugated organic materials. In this study, a series of dodecyl-substituted PheDOT derivatives was synthesized through lithiation–alkylation reactions. Both mono- and di-dodecyl-substituted PheDOT derivatives were obtained. The mono-substituted derivative was subsequently subjected to stannylation, affording a product assigned, on the basis of the reaction sequence and 1H NMR data, as the proposed tributylstannyl-PheDOT intermediate. The synthesized compounds were characterized using ¹H NMR, ¹³C NMR, and mass spectrometric techniques, depending on the data available for each compound. The alkylation reaction afforded 1,3-didodecylbenzo[b]thieno[3,4-e][1,4]dioxine (di-dodecyl-PheDOT) and 1-dodecylbenzo[b]thieno[3,4-e][1,4]dioxine (mono-dodecyl-PheDOT) in isolated yields of 8.2% and 32%, respectively. Under palladium-catalyzed coupling conditions, two PheDOT-based conjugated dimers, 3,3’-didodecyl-1,1’-bibenzo[b]thieno[3,4-e][1,4]dioxine (B2) and 3-dodecyl-1,1’-bibenzo[b]thieno[3,4-e][1,4]dioxine (B4) were isolated and characterized by spectroscopic analyses. The formation of these dimers supports the suitability of alkyl-functionalized PheDOT derivatives as precursors for the construction of larger π-conjugated structures. In addition, several PheDOT-derived conjugated structures and plausible coupling products were investigated using Density Functional Theory (DFT) calculations. The investigated systems were selected on the basis of experimentally observed mass spectrometric data and proposed coupling pathways. The incorporation of dodecyl substituents provided PheDOT derivatives that were sufficiently soluble in common organic solvents to allow chromatographic purification and spectroscopic characterization. These results expand the range of structurally defined alkyl-functionalized PheDOT derivatives and provide useful molecular building blocks for the future development of π-conjugated PheDOT-based systems.