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

Poly[(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.