Room temperature methods of direct arylation for conjugated polymer and small molecule synthesis

Abstract

Direct arylation polymerization (DArP) offers numerous benefits over classical methods of crosscouplingpolymerization, although improvements are still warranted to increase simplicity and reduce cost. Room temperature transformations are an attractive approach, requiring an efficient C-H arylation process while providing insights into mechanistic features allowing for good reactivity with reduced thermal energy availability. This work investigates room temperature direct arylation, emphasizing the underlying mechanisms that differ between room temperature conditions and the more common elevated temperatures. Two different transformations are investigated as room temperature direct arylation methods for heterobiaryls: DArP-prepared polyindole and benzofuran direct arylation. Both conditions are shown to proceed through nontraditional mechanisms, facilitating room temperature reactivity. Despite good small molecule regioselectivity, regiodefects are high in polyindole and regioselectivity is a concern should the benzofuran method be used for DArP. These results demand greater study into approaches for improving selectivity. The unpredicted regiodefects in these polymerizations provide a strategy for understanding selectivity and reactivity trends not readily observable in the corresponding small molecule reaction due to the exceptional monomer conversion required for polymerization.