A New Method for the Synthesis of Carboxylic Esters and Lactones with Di-2-thienyl Carbonate (2-DTC) by the Promotion of DMAP and Iodine

The esterification of carboxylic acids with alcohols by using di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) proceeded smoothly to afford the corresponding esters in good-to-high yields along with 2(5H)-thiophenone. This esterification was accelerated by the addition of an equimolar amount of iodine to afford the esters in higher yields within a shorter reaction time. Further, cyclization of ω-hydroxycarboxylic acids with an equimolar amount of 2-DTC in the presence of a catalytic amount of DMAP, followed by the addition of 1–4 equimolar amounts of iodine, afforded the corresponding lactones in good-to-high yields under mild conditions. This method was successfully employed in the synthesis of erythro-aleuritic acid lactone.