Density Functional Theory Mechanistic Study of Boron‐Catalyzed N‐Alkylation of Amines with Formic Acid: Formic Acid Activation by Silylation Reaction

Abstract

New methodology for the alkylation of amines is an intriguing issue in both academia and industry. Recently, several groups reported the metal-free B(C F ) -catalyzed N-alkylation of amines, but the mechanistic details of these important reactions are unclear. Herein, a computational study was performed to elucidate the mechanism of the N-alkylation of amines with formic acid catalyzed by the Lewis acid B(C F ) in the presence of hydrosilane. We found that the reaction started with the activation of formic acid through a novel model. Then, the high electrophilicity of the C center of the formic acid unit and the nucleophilic character of the amine resulted in a C-N coupling reaction. Finally, two sequential silyl-group and H transfer steps occurred to generate the final product. Upon comparing the reaction barrier and the hydrogenation of indole, our mechanism is more favorable than that proposed by the group of Yu and Fu.

A comprehensive study of indole catalytic hydrodenitrogenation under hydrothermal conditions

“…Figure 7 shows the reaction network among the identified products. Methylation of indole and its reverse reaction are represented by path 1 and path 1r, respectively 18,29 . The hydrogenation from indole to indoline was the first step before removing the N element of indole (path 2).…”

“…Methylation of indole and its reverse reaction are represented by path 1 and path 1r, respectively. 18,29 The hydrogenation from indole to indoline was the first step before removing the N element of indole (path 2). Given that the dehydrogenation reaction from indoline to indole was widely reported in indole HDN, 29a,30 its reverse reaction is also included in this network as path 2r.…”

Boron Catalysis in the Transformation of Carboxylic Acids and Carboxylic Acid Derivatives

“…DFT calculations suggested sequential silyations of formic acid to form cationic species 54 . Subsequently, addition of amine to the cationic carbon and sequential reductive C−O bond cleavage produces the N ‐methyl product 56 [31b] …”