Abstract :
[en] The metal-free coupling of propargylic alcohols with carbon dioxide catalysed by guanidine derivatives was investigated in detail through the combination of online kinetic studies by in-situ ATR-IR spectroscopy and DFT calculations. Bicyclic guanidines, namely TBD and MTBD, are effective catalysts for the conversion of 2-methyl-3-butyn-2-ol to α-methylene cyclic carbonate and oxoalkyl acyclic carbonate under mild reaction conditions. The lower selectivity of TBD in comparison with MTBD towards the formation of α-methylene cyclic carbonate was elucidated from DFT calculations and is related to the bifunctional activity (base/H-bond donor) of TBD decreasing the Gibbs free energy of the reaction path for the formation of the acyclic carbonate.
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