Triflic Acid‐Assisted Regioselective Bromination of Quinoxaline Derivatives Enables a Facile Synthesis of Polymer PTQ10

AbstractPoly[(thiophene)‐alt‐(6,7‐difluoro‐2(2‐hexyldecyloxy)quinoxaline)] (PTQ10) emerges as a promising candidate for donor materials in organic solar cells (OSCs) due to its high efficiency, simplified synthesis, and cost‐effectiveness. The acceptor unit of PTQ10 is derived from the alkylation of 5,8‐dibromo‐6,7‐difluoroquinoxaline‐2‐ol, emphasizing the importance of its economical synthesis for commercial viability. This study investigates triflic acid‐assisted regioselective bromination of quinoxaline derivatives and proposes an alternative synthetic pathway for PTQ10. The developed route benefits from concise synthetic steps, a dependable procedure, and high overall yield. Starting with the condensation of 4,5‐difluorobenzene‐1,2‐diamine with ethyl oxoacetate to yield 6,7‐difluoroquinoxaline‐2‐ol, subsequent triflic acid‐assisted regioselective bromination produces 5,8‐dibromo‐6,7‐difluoroquinoxaline‐2‐ol in high yield. Alkylation under Mitsunobu reaction conditions yields 5,8‐dibromo‐6,7‐difluoro‐2‐(2‐hexyldecyloxy)quinoxaline, followed by polymerization with 2,5‐distannylated thiophene under Stille reaction conditions to afford PTQ10. This research provides insights into efficient synthetic strategies for PTQ10, advancing its potential for commercial application in OSCs.