Manganese Catalyzed Hydrogenation of Azo (N=N) Bonds to Amines

Abstract

We report the first example of homogeneously catalyzed hydrogenation of the N=N bond of azo compounds using a complex of an earth‐abundant‐metal. The hydrogenation reaction is catalyzed by a manganese pincer complex, proceeds under mild conditions, and yields amines, which makes this methodology a sustainable alternative route for the conversion of azo compounds. A plausible mechanism involving metal‐ligand cooperation and hydrazine intermediacy is proposed based on mechanistic studies.

Manganese-catalyzed hydrogenation, dehydrogenation, and hydroelementation reactions

“…Milstein and coworkers demonstrated the hydrogenation of azo compounds to amines in 2021. 152 (NNP)Mn( i )-complex Mn37 catalyzes this transformation with a TON of up to 31 (Scheme 25). However, the developed protocol was only applicable to aromatic azo compounds.…”

Hydrogenation and Cross-Coupling Reactions Catalyzed by Mn, Fe, and Co Aromatic Pincer Complexes

“…More recently, Milstein et al have described how complex 36 can be employed in the addition of dihydrogen to the NN bond of azo compounds to generate amines under mild reaction conditions . This procedure is a key transformation since amines are useful intermediates , and the hydrogenation of azo compounds provides a sustainable option and an alternate route to the dye degradation process .…”

“…More recently, Milstein et al have described how complex 36 can be employed in the addition of dihydrogen to the NN bond of azo compounds to generate amines under mild reaction conditions . This procedure is a key transformation since amines are useful intermediates , and the hydrogenation of azo compounds provides a sustainable option and an alternate route to the dye degradation process . The catalytic hydrogenation of azobenzene derivatives to the corresponding aniline derivatives was possible using pincer compound 36 (3 mol %) in the presence of t BuOK under H 2 (30 bar) at 130 °C for 48 h in THF (Table ).…”

Chemodivergent coupling of azoarenes with benzyl alcohols via a borrowing hydrogen strategy using a well-defined nickel catalyst

“…Prominent examples of the hydrogenative transformation of azoarenes to anilines or heterocycles are known. 12 Despite these advances, the use of azo compounds as a nitrogen source for the sustainable synthesis of imines and amines using a molecularly defined catalyst is unknown. In this regard, herein, we report an earth-abundant nickel catalytic system for the (de)hydrogenative coupling of azoarenes with benzyl alcohols via a borrowing-hydrogen (hydrogen-auto transfer) strategy (Fig.…”