Cu(I) Mediated Azidation of Halobenzenes, and Cu Catalysed Selective Azide Reduction to Corresponding Amines

• Published in: Advanced synthesis & catalysis 2022-09, Vol.364 (17), p.2957-2971
• Main Authors: Roemer, Max, Luck, Ian, Proschogo, Nicholas
• Format: Article
• Language: English
• Subjects: Amines; Aniline; Aromatic compounds; Azides; Bromides; Click chemistry; Copper; Ethanol; Halobenzenes; Nanostructures; Reduction; Sodium azides; Stirring; Synthetic methods
• ISSN: 1615-4150; 1615-4169
• DOI: 10.1002/adsc.202200594

Aryl amines are synthesized from halobenzenes via copper mediated reactions employing sodium azide under mild conditions in ethanol/water. The reaction proceeds stepwise via the aryl azide, which is reduced to the corresponding amine in‐situ. The methodology allows syntheses of amines from corresponding para‐, meta‐ and ortho‐bromobenzenes bearing electron withdrawing groups. Bifunctional halobenzenes bearing alkanoyl chains with terminal bromides are selectively transformed, generating an aniline and an aliphatic azide, as this azide position is stable to reduction. A one‐pot multistep sequence for preparation of the target amines was designed. The azide formation is mediated by CuI while elemental Cu is generated simultaneously, which is deposited onto the employed PTFE stirring bar used in the reaction. The Cu films were quantified and analysed by SEM/EDS. The Cu, either deposited or in solution, is responsible for the azide reduction, possibly involving nitrene intermediates. An application of the modified stirring bars as a heterogeneous catalyst for a click reaction is demonstrated.