Semiconducting Polymers via Microwave‐Assisted Suzuki and Stille Cross‐Coupling Reactions

A fully conjugated para ‐phenylene ladder polymer ( P1 ) and the alternating copolymers {2,7‐[9,9‐bis(2‐ethylhexyl)fluorene]‐5,5′‐(2,2′‐bithiophene)} ( P3 ) and {2,7‐[9,9‐dioctylfluorene]‐5,5′‐(2,2′‐bithiophene)} ( P4 ) have been prepared via metal‐mediated cross‐coupling reactions, using microwaves as a heat source. The procedure, which yields polymeric material in ca. ten minutes, has no adverse effects on the quality of the polymers and displays a high degree of reproducibility. Transfer of the optimized conditions to the synthesis of a new naphthalene‐based polyarylene‐ketone ( P2 ) and a (1,5‐dioctoxynaphthylene‐2,6‐diyl‐ alt ‐2,2′‐bithiophene‐5,5′‐diyl) copolymer ( P5 ) confirmed the versatility of the procedure and the dramatic reduction in reaction times compared with conventional heating. In the case of the Stille‐type coupling reaction of the electron‐rich, less reactive dibromo monomer 1,5‐dioctoxy‐2,6‐dibromo‐naphthalene, the microwave‐assisted protocol results in a marked increase in both yield and molecular weight.