Electrosynthesis of Diaminobiaryls

Electrosynthesis of Diaminobiaryls

Author: Angewandte Chemie International Edition

2,2′-Diaminobiaryls and their derivatives are common structural motifs, for example, in organic ligands and natural products. However, their synthesis can be difficult. Nonsymmetric products, in particular, require tedious synthetic protocols. A direct oxidative treatment of aniline and its derivatives usually results in the pitch-black electrically conductive polyaniline. This reaction takes place directly on anodes.

Siegfried R. Waldvogel, University of Mainz, Germany, and colleagues have developed a direct and selective electrochemical cross-coupling of aniline derivatives. This carbon-carbon bond formation requires no leaving groups, metal catalysts, or reagents. The team used a simple beaker with two electrodes (e.g., made from glassy carbon) and a constant current. The protective groups (PG) for the amino groups are common and simple (e.g., acetyl). The selectivity for the cross-coupling is based on a solvent effect of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), which modulates the nucleophilicity of the individual coupling components, and is the key for a clean electrochemical synthesis.

The electrochemical preparation shows good yields, and the experimental set-up is very simple. A broad scope of diaryldiamines (pictured) can be accessed by this method.


 

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