Bryan Zachary J, Hall Ariana O, Zhao Carolyn T, Chen Jing, McNeil Anne J
Department of Chemistry and Macromolecular Science and Engineering Program, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States.
ACS Macro Lett. 2016 Jan 19;5(1):69-72. doi: 10.1021/acsmacrolett.5b00746. Epub 2015 Dec 21.
Catalyst-transfer polycondensation (CTP) is a relatively new method for synthesizing conjugated polymers in a chain-growth fashion using transition metal catalysis. Recent research has focused on screening catalysts to broaden the monomer scope. In this effort, small molecule reactions have played an important role. Specifically, when selective difunctionalization occurs, even with limiting quantities of reaction partner, it suggests an associative intermediate similar to CTP. Several new chain-growth polymerizations have been discovered using this approach. We report herein an attempt to use this method to develop chain-growth conditions for synthesizing poly(2,5-bis(hexyloxy)phenylene ethynylene) via Sonogashira cross-coupling. Hundreds of small molecule experiments were performed and selective difunctionalization was observed with a Buchwald-type precatalyst. Unexpectedly, these same reaction conditions led to a step-growth polymerization. Further investigation revealed that the product ratios in the small molecule reactions were dictated by reactivity differences rather than an associative intermediate. The lessons learned from these studies have broad implications on other small molecule reactions being used to identify new catalysts for CTP.
催化转移缩聚（CTP）是一种相对较新的方法，用于以链增长方式使用过渡金属催化合成共轭聚合物。最近的研究集中在筛选催化剂以拓宽单体范围。在这项工作中，小分子反应发挥了重要作用。具体而言，当发生选择性双官能化时，即使反应伙伴的量有限，也表明存在类似于CTP的缔合中间体。使用这种方法已经发现了几种新的链增长聚合反应。我们在此报告尝试使用该方法通过Sonogashira交叉偶联开发用于合成聚（2,5-双（己氧基）亚苯基乙炔）的链增长条件。进行了数百次小分子实验，并使用Buchwald型预催化剂观察到了选择性双官能化。出乎意料的是，这些相同的反应条件导致了逐步聚合。进一步的研究表明，小分子反应中的产物比例是由反应性差异而非缔合中间体决定的。从这些研究中学到的经验教训对用于鉴定CTP新催化剂的其他小分子反应具有广泛的影响。
