Co‐Catalyzed Metal‐Ligand Cooperative Approach for N ‐alkylation of Amines and Synthesis of Quinolines via Dehydrogenative Alcohol Functionalization

Herein we report a cobalt‐catalyzed sustainable approach for C−N cross‐coupling reaction between amines and alcohols. Using a well‐defined Co‐catalyst 1 a bearing 2‐(phenyldiazenyl)‐1,10‐phenanthroline ligand, various N ‐alkylated amines were synthesized in good yields. 1 a efficiently alkylates diamines producing N , N′ ‐dialkylated amines in good yields and showed excellent chemoselectivity when oleyl alcohol and β‐citronellol, containing internal carbon‐carbon double bond were used as alkylating agents. 1 a is equally compatible with synthesizing N ‐heterocycles via dehydrogenative coupling of amines and alcohols. 1 H ‐Indole was synthesized via an intramolecular dehydrogenative N ‐alkylation reaction, and various substituted quinolines were synthesized by coupling of 2‐aminobenzyl alcohol and secondary alcohols. A few control reactions and spectroscopic experiments were conducted to illuminate the plausible reaction mechanism, indicating that the 1 a ‐catalyzed N ‐alkylation proceeds through the borrowing hydrogen pathway. The coordinated arylazo ligand participates actively throughout the reaction; the hydrogen eliminated during dehydrogenation of alcohols was set aside in the ligand backbone and subsequently gets transferred in the reductive amination step to imine intermediates yielding N ‐alkylated amines. On the other hand, 1 a ‐catalyzed quinoline synthesis proceeds through dehydrogenation followed by successive C−C and C−N coupling steps forming H 2 O 2 as a by‐product under air.