Boron-Catalyzed N-Alkylation of Arylamines and Arylamides with Benzylic Alcohols

Abstract

A sustainable boron-based catalytic approach for chemoselective N-alkylation of primary and secondary aromatic amines and amides with primary, secondary, and tertiary benzylic alcohols has been presented. The metal-free protocol operates at low catalyst loading, tolerates several functional groups, and generates H2O as the sole byproduct. Preliminary mechanistic studies were performed to demonstrate the crucial role of boron catalyst for the activation of the intermediate dibenzyl ether and to identify the rate-determining step.

Mimicking transition metals in borrowing hydrogen from alcohols

“…S110, ESI ‡) rather than the generation of carbocations or ethers as reported for other metal-free N-alkylation mechanisms. 63,64 Such an observation indicates that the borrowing hydrogen mechanism is operative. Furthermore, to understand the role of KO t Bu, we have treated benzyl alcohol, 2a, with 1 equivalent N-benzylideneaniline, 5a, along with 10 mol% (N,O)-PLY and only 20 mol% KO t Bu resulting in 88% N-benzylaniline, 3a, aer isolation (Scheme 3a).…”

Brønsted Acid‐Catalysed Dehydrative Substitution Reactions of Alcohols

“…In 2019, Chan and co‐workers showed that electron‐rich primary anilines undergo selective N ‐alkylation in nitromethane with a range of secondary and tertiary benzylic alcohols catalysed by BCF 4 (10 mol %) [9] . Subsequently, Maji disclosed the BCF 4 (1 mol %) promoted dehydrative alkylation of secondary anilines with a range of electron‐rich primary, secondary or tertiary benzylic alcohols [69] . The method was also applicable to the monoalkylation of primary sulfonamides.…”

“…[9] Subsequently,M aji disclosed the BCF 4 (1 mol %) promoted dehydrative alkylation of secondary anilines with ar ange of electron-rich primary,s econdary or tertiary benzylic alcohols. [69] The method was also applicable to the monoalkylation of primary sulfonamides.…”

Interdigital Micromixer for Selective N-Monoalkylation of Anilines in a Microflow System

“…Low reaction selectivity is the main cause . Typically, once alkylation of primary amine occurs, the resulting secondary amine with stronger alkalinity will compete with the primary amine, resulting in the formation of a tertiary amine . In severe cases, quaternary ammonium compounds will be obtained .…”