Cobalt-Catalyzed Direct Alkoxylation of Indoles.

Cobalt(II) salt as a non-noble metal catalyst has been widely used in direct C-H bond functionalization in recent years. In this work, we developed a cobalt-catalyzed C-H cleavage and alkoxylation of indoles with alcohols for the rapid construction of 2-alkoxylindole scaffolds. In the presence of Co(acac) 2 as the catalyst, the reaction proceeds well to give a variety of 2-alkoxylindole derivatives in moderate to high yields. Control experiments suggest that a radical process might be involved in the reaction and the Co(III) species is the active catalyst.