Cu-catalyzed carboxylation of organoboronic acid pinacol esters with CO 2 .

Chemical fixation of CO ₂ has received much attention. In particular, catalytic C-C bond formation with CO ₂ giving carboxylic acids is of great significance. Among the CO ₂ fixation methods, multiple carboxylation is one of the challenging subjects. Here we investigated the Cu-catalyzed carboxylation of a variety of boronic acid pinacol esters (C(sp ² )-, C(sp ³ )-, and C(sp)-B compounds) with CO ₂ , which efficiently provided the corresponding products, including aryl, alkenyl, alkyl, and alkynyl carboxylic acids. This carboxylation was also applicable to multiple CO ₂ fixation giving di- and tri-carboxylic acids under robust reaction conditions (totally 29 examples).