Selective Organocatalytic Preparation of Trimethylene Carbonate from Oxetane and Carbon Dioxide

The organocatalytic coupling of oxetanes and carbon dioxide (CO 2 ) offers a sustainable route to poly(trimethylene carbonate)s and/or functional six-membered cyclic carbonate monomers. This transformation is more challenging than when using more strained epoxide comonomers and even more so when it is performed using metal-free routes. Herein, we report an organocatalytic oxetane/CO 2 coupling procedure that enables the selection of cyclic carbonate or polymer from a common intermediate. Using a novel I 2 -based binary catalyst system, cyclic carbonate with high selectivity (up to 94%) was obtained at 55 °C, whereas simply changing the temperature to 105 °C yielded the polycarbonate with M n of up to 6.4 kDa, thus showing that either trimethylene carbonate or its concomitant polycarbonate product can be selected solely by the manipulation of the reaction conditions.