Iridium(I)-Catalyzed C-C and C-N Bond Formation Reactions via the Borrowing Hydrogen Strategy.

Iridium(I) complexes having an imidazol-2-ylidene ligand with benzylic wingtips efficiently catalyzed the β-alkylation of secondary alcohols with primary alcohols and acceptorless dehydrogenative cyclization of 2-aminobenzyl alcohol with ketones through a borrowing hydrogen pathway. The β-alkylated alcohols, including cholesterol derivatives, and substituted quinolines were obtained in good yields by using a minute amount of the catalyst with a catalytic amount of NaOH or KOH under the air atmosphere, liberating water (and H2 in the case of quinoline synthesis) as the sole byproduct. Notably, this system demonstrated turnover numbers of 940 000 (for β-alkylation of secondary alcohols with primary alcohols by using down to 0.0001 mol % = 1 ppm of the catalyst) and 9200 (acceptorless dehydrogenative cyclization of 2-aminobenzyl alcohol with ketones).