Meta halogenation of 1,3-disubstituted arenes via iridium-catalyzed arene borylation

We report the meta halogenation of 1,3-disubstituted arenes to form 3,5-disubstituted aryl bromides and chlorides by using iridium-catalyzed arene borylation chemistry. Iridium-catalyzed borylation of arenes with B(2)pin(2), followed by reaction of the boronic ester with copper(II) bromide or chloride converts arylboronic esters to the corresponding aryl halides. A variety of arenes containing alkoxy, alkyl, halogen, nitrile, ester, amide, and pivaloyl and TIPS-protected alcohols were converted to the corresponding 3,5-disubstituted aryl bromides and chlorides in yields ranging from 46% to 85%. In addition, 2,6-disubstituted and 3-substituted pyridines were converted to the 4-halo and 5-halopyridines, respectively. The utility of this methodology was demonstrated by the formal conversion of nicotine to Altinicline in three steps with an overall yield of 61% using meta bromination of nicotine as the first step.