Manganese‐Triazolylidene Catalysis for The Synthesis of 1,2,3,4‐Tetrahydroquinoxalines and Selective Alkylation of Diamines and Anilines with Alcohols and Diols

Abstract

AbstractIn this study, 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], which 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‐pyridine methanol, 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 both selective monoalkylation and dialkylation of a broad range of aniline derivatives using aliphatic diols as alkylating agents. This method provides the corresponding alkylated amines in excellentyields, typically between 81% to 99%, thereby underscoring its efficiency. The straighforward nature of the method, together with the use of readily available manganese catalyst, makes this strategy particularly appealing and suggests significant potential for wider use in the synthesis of parmaceutically relevant molecules.