Oxidative NHC Catalysis: An Unconventional Tool for Polymers Synthesis

N-heterocyclic carbene (NHC) catalysis under oxidative conditions can be efficiently employed in the synthesis of fossil- and bio-based polyesters and polyamides starting from dialdehydes and diols/diamines (Scheme 1, a, b). The peculiarity of the methodology relies in the activation under mild reaction conditions of readily available dialdehydes, through the generation of highly reactive acyl azolium intermediates, via Breslow intermediate oxidation, in the presence of an external oxidant. Moreover, the employment of highly diluted oxidative conditions allows the direct selective access to macrocyclic oligoesters (MCOs) (Scheme1, c), valuable intermediates for the synthesis of high molecular weight linear polyesters through entropy-driven ringopening polymerization (ED-ROP). According to this strategy, exploiting the presence of both aldehydic and alcoholic functionalities on the same molecule, the direct selfcondensation of the platform chemical HMF was performed, synthesizing HMF-based cyclic oligoesters which were in turn converted to poly(hydroxymethylfuroate) (PHMF) through ED-ROP process.