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In this study, the impact of ester side group regiochemistry on electronic and conformational properties of regioregular polyfurans was explored. A derivative with alternating head‐to‐head and tail‐to‐tail orientation of the side groups was synthesized and compared with its head‐to‐tail analogue, and these were benchmarked against the related regioregular poly(3‐hexylfurans). The study revealed that alkyl ester side groups in a head‐to‐head orientation will create significant steric strain as compared with linear alkyl chains with identical regiochemistry. Though the head‐to‐head ester side groups lead to twisting along the polymer backbone, they also produce a protective effect against photodegradation in comparison with a poly(3‐hexylfuran). Altogether, the work highlights how side groups can impact conformational properties and stability of polyfurans.

Substituted propargyl acetates are converted into 4‐boryl‐2(5H)‐furanones upon thermolysis in the presence of an N‐heterocyclic carbene borane (NHC‐borane) and di‐tert‐butyl peroxide. The acetyl methyl group is lost during the reaction as methane. Evidence suggests that the reaction proceeds by a sequence of radical events including: 1) addition of an NHC‐boryl radical to the triple bond; 2) cyclization of the resultant β‐borylalkenyl radical to the ester carbonyl group; 3) β‐scission of the so‐formed alkoxy radical to provide the 4‐boryl‐2(5H)‐furanone and a methyl radical; and 4) hydrogen abstraction from the NHC‐borane to return the initial NHC‐boryl radical and methane.