Direct Synthesis of Diphenylamines from Phenols and Ammonium Formate Catalyzed by Palladium.

Arylamines are commercially and synthetically useful compounds with a wide variety of applications. Their preparation has been traditionally achieved using metal-catalyzed C-N coupling reactions with aryl halides. In this work, 17 different diarylamines are prepared from phenols by using ammonium formate as the aminating reagent. Phenolic compounds are more desirable feedstocks, owing to their availability from lignin, making them valuable biorenewable alternatives to aryl halides. Ammonium formate is found to be a convenient surrogate for ammonia and a useful aminating reagent for phenols. Diarylamine products are obtained in good to excellent yields while only water and CO2 are generated as byproducts of the transformation.