Synthesis and Design of Unsymmetrical Quinoxaline-Based Oligomer with Tunable Backbone

Quinoxalines, also named benzopyrazines, are an important class of nitrogen-containing heterocyclic compounds. Due to their multifaceted electronic and structural features, quinoxalines derivatives have been high priority target scaffold in various studies over the past years, aiming to improve the properties of several materials and drugs. New oligomers based on quinoxaline units were successfully synthesized through multistep reactions using Wittig coupling, affording (E)-(quinoxalin-2-yl)ethene oligomers. The elaborated two-step oligomerization process, containing repetitive sequences of selective oxidations and Wittig coupling reactions, ensured the selective assembly of quinoxaline-based monomers to form various oligomers up to 3+3 units and 4 units. Furthermore, Stille coupling was also applied to generate C-C quinoxalines connections, providing efficient and countless possibilities for oligomer building. C-H activation reaction using titanium complexe Cp2Ti{η2-C2(Si(CH3)3)2} was also evaluated, transforming trimeric quinoxaline-based oligomers into asymmetric hexaazatrinaphthylene (HATN).