An Efficient Homogenized Ruthenium(II) Pincer Complex for N-Monoalkylation of Amines with Alcohols

An ionic 2,6-bis(imidazo[ 1,2-alpha] pyridin-2-yl) pyridine-based N<^>N<^>N pincer ruthenium(II) complex exhibited high efficiency in the C-N bond formation between amines and alcohols by the borrowing hydrogen (BH) or hydrogen autotransfer (HA) concept. The synthetic protocol selectively generated monoalkylated amines without formation of tertiary amines during the reaction. The unique selectivity enabled the formation of symmetrically and asymmetrically substituted diamines. This methodology features several advantages including a low catalyst loading (as low as 0.5 mol-%), a short reaction time (as short as 2 h), and excellent N-monoalkylation selectivity.