C-H bond functionalization of aryl acids and amines by 'on-water' reaction: Bi-dentate directing group enabled synthesis of biaryl and m-teraryl carboxamides.

Abstract

Herein, we report a palladium-catalyzed 'on-water' methodology for the synthesis of biaryl and m-teraryl derivatives of aryl carboxamides by selective mono and bis C-H bond functionalization. 8-aminoquinoline and 2-thiomethylaniline were used as directing groups for C-H bond functionalization of aryl carboxamides with various aryl and alkyl iodides using 3.0-4.0 mol% of Pd(OAc)2as catalyst and water as the solvent resulting in 45-97% isolated yields of the mono and bis C-H bond functionalized products. Using an 8-aminoquinoline carboxamide core, C-H bond functionalization of indole-3-carboxylic acid and a late-stage functionalization of aspirin molecule have also been carried out. Reactions of benzyl/naphthyl picolinamides with aryl iodides gave 60-96% yield of the arylated products using the picolinamide directing group. Moreover, the insoluble nature of products in an aqueous medium enabled us to explore the reusability of the solvent, i.e., water and the catalyst. Control experiments and structural studies were carried out which confirmed thein situformation of unique palladacycles during the reaction. Removal of the directing groups has been carried out to convert the functionalized products into amines and fluorenone compounds useful in industrial and pharmaceutical applications.