An efficient one-pot access to poly(arylene ethynylene) homopolymers: Use of the Bu3Sn-moiety as a recyclable carrier to introduce the ethynyl unit into the chain

The palladium-catalyzed Stille coupling of an aromatic diiodide with half a n equivalent of tributyl(ethynyl)tin results in a complex mixture containin g the diethynylaromatic compound, the iodo(ethynyl)aromatic compound, unrea cted diiodide and the tributyltin iodide side product. Addition of LDA to t his mixture, while leaving the iodoaromatic moieties unaffected, causes dep rotonation of the ethynyl functionalities, which immediately recombine with tributyltin iodide to form a mixture of bis-(tributylethynyltin)aromatic, iodo(tributylethynyltin)aromatic, and unchanged diiodide. Being the palladi um catalyst still active, it is sufficient to warm up this mixture to obtai n the coupling of the tributylethynyltin and iodo moieties resulting in the formation of a poly(arylene ethynylene) polymer. Isolation of the polymer is easily and rapidly achieved by precipitation, while distillation of the mother liquor allows recovery of the tributyltin iodide side product. The l atter can be utilized for the preparation of new tributyl(ethynyl)tin, thus allowing a convenient turnover of the tributyltin moiety. (C) 2000 John Wi ley & Sons, Inc.