Divergent Dehydrogenative Coupling of Indolines with Alcohols

The dehydrogenative coupling of indolines with alcohols catalyzed by an iridium complex has been achieved to afford both N- and C3-alkylated indoles selectively, by simply changing the addition time of a base additive. The iridacycle catalyst plays multiple roles in these reactions, which dehydrogenates both amines and alcohols and catalyzes the coupling reactions. Mechanistic studies reveal that a borrowing hydrogen-dehydrogenation process and a dehydrogenation-borrowing hydrogen process are involved in N-alkylation and C3-alkylation reactions, respectively. The C3-alkylation reaction involves the direct coupling of two sp3 carbon centers.