Synthesis 2018; 50(23): 4617-4626
DOI: 10.1055/s-0037-1610252
paper
© Georg Thieme Verlag Stuttgart · New York

Efficient and Versatile Catalytic Systems for the N-Methylation of Primary Amines with Methanol Catalyzed by N-Heterocyclic Carbene Complexes of Iridium

Genki Toyooka
,
Akiko Tuji
,
Ken-ichi Fujita*
Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan   Email: fujita.kenichi.6a@kyoto-u.ac.jp
› Author Affiliations
This work was supported by JSPS KAKENHI Grant Number JP16H01018 and JP18H04255 in Precisely Designed Catalysts with Customized Scaffolding and Nagase Science and Technology Foundation.
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Publication History

Received: 25 May 2018

Accepted after revision: 25 July 2018

Publication Date:
30 August 2018 (online)


Abstract

Efficient and versatile catalytic systems were developed for the N-methylation of both aliphatic and aromatic primary amines using methanol as the methylating agent. Iridium complexes bearing an N-heterocyclic carbene (NHC) ligand exhibited high catalytic performance for this type of transformation. For aliphatic amines, selective N,N-dimethylation was achieved at low temperatures (50–90 °C). For aromatic amines, selective N-monomethylation and selective N,N-dimethylation were accomplished by simply changing the reaction conditions (presence or absence of a base with an appropriate catalyst). These findings can be used to develop methods for synthesizing useful amine compounds having N-methyl or N,N-dimethyl moieties.

Supporting Information