N‐alkylation of benzamides/sulfonamides using alcohols via borrowing hydrogen approach by well‐defined Pd (II) pincer complexes

Abstract

The development of green, sustainable, and atom‐economical procedure for the construction of amides via C‐N bond formation is a high priority in synthetic organic community. In this research article, we demonstrate a simple and an efficient catalytic protocol for N‐alkylation of benzamides/sulfonamides using aromatic primary alcohols as coupling partners through borrowing hydrogen (BH) strategy by employing newly constructed palladium (II) O^N^O pincer complexes. All the palladium complexes are characterized by analytical and spectral methods (FT‐IR, NMR, and HRMS). Further, the solid‐state molecular structures of the complexes have been well authenticated by single‐crystal XRD studies. The present N‐alkylation protocol is facile, worked in low catalyst loading (0.5 mol%), and furnishes the desired N‐alkyl amides with excellent yields up to 92%. In this methodology, the reaction proceeds via the formation of intermediates such as aldehyde and (E)‐N‐benzylidenebenzamide with a release of water as ecological by‐product. The control experiments and plausible mechanistic investigations suggested that the coupling reaction was initially proceeds via dehydrogenation of alcohol and generate the alkylated products through hydrogen auto‐transfer. A large‐scale synthesis of N‐(4‐methoxybenzyl)benzamide proves the effectiveness of the Pd (II) pincer catalysts.