Triazolylidene Manganese Complex as Efficient Catalyst for Borrowing Hydrogen Reactions

Herein, we present manganese‐catalyzed borrowing hydrogen processes for the efficient synthesis of 1,2,3,4‐tetrahydroquinoxalines and the selective N,N´‐dialkylation of o‐phenylenediamines with alcohols. A Mn(I)‐catalyzed method for synthesizing 1,2,3,4‐tetrahydroquinoxalines via the direct reaction of o‐phenylenediamine with diols under mild conditions (80 °C) is described. The catalyst, [Mn(bis‐1,2,3‐triazolylidene)(CO)3Br], features a bidentate triazolylidene ligand, is air‐stable, easy to prepare, and exhibits broad activity across a wide range of substrates. Additionally, this Mn‐triazolylidene complex efficiently catalyzes the N,N´‐dialkylation of a variety of o‐and p‐phenylenediamines with a range of primary alcohols, such as benzyl alcohols, furfuryl alcohol, and 3‐pyridinemethanol, using catalytic amount of base and mild conditions (100 °C, 6 h). Notably, this method enables the derivatization of the important drug molecule Dapson, showcasing its practical utility. The catalyst also allows the selective dialkylation and monoalkylation of aniline with aliphatic diols, providing the corresponding alkylated amines in excellent yields.