Tin- or titanium-catalyzed dimethyl carbonate synthesis from carbon dioxide and methanol: Large promotion by a small amount of triflate salts

The Bu2SnO- or Ti(O-i-Pr)4-catalyzed dimethyl carbonate (DMC) synthesis starting from methanol, carbon dioxide, and dimethyl ketal was remarkably accelerated by the addition of a small amount of [Ph2NH2]OTf (N:Sn = 1:10); conventional acids such as H2SO4, HCl, and H3PO4 were not effective to promote the DMC synthesis.