Nickel‐Catalyzed Selective Hydrazoarenes and Aminoarenes Formation from Azoarenes Using Ammonia–Borane

A well-characterized, phosphine-free, molecular nickel catalyst bearing a terpyridine backbone is employed for the selective transfer hydrogenative cleavage of the ─N═N─bond of azoarene to hydrazoarenes and aminoarenes using ammonia borane as an efficient hydrogen source.

Abstract

Herein, we report the synthesis of an air-stable, phosphine-free NNN-based nickel(II) pincer complex that catalyzed the generation of diverse hydrogenated products from azoarenes using ammonia borane (AB) as a transfer hydrogenating source, facilitating at room temperature. The synthetic protocol tolerates the transfer hydrogenation (TH) of various azo-derived substrates, especially bearing reducible functional groups. The preliminary mechanistic investigation studies revealed the crucial role of nickel catalyst in the TH of the azo-substrates using AB and ethanol, which generates the boron-alkoxide by-products. The significant advantage of this study highlights the utilization of nickel catalyst for the complete N═N cleavage of azoarenes to generate aminoarenes, assisted at base-free, mild reaction conditions.

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