Catalytic methoxylation of aryl halides using 13 C- and 14 C-labeled CO 2 .

The functionalization of carbon dioxide (CO 2 ) into high-value building blocks is a relevant topic in carbon isotope labeling, where CO 2 is the primary carbon source. A catalytic methoxylation of aryl halides directly from [ 13 C] and [ 14 C]CO 2 is reported. Relying on the intermediacy of the methoxyborane BBN-OCH 3 , as a new secondary nucleophilic labeled source, this strategy allowed labeling of a series of substrates, including challenging pharmaceuticals containing tertiary alkyl amine substituents.