N-Alkylated amines are an essential class of compounds in chemistry. Classic synthetic pathways proceed via nucleophilic substitution and involve the use of alkyl halides. As a result, halide salts are produced in stoichiometric amounts, resulting in an overall low atom economy. In addition to that, poor selectivity is often obtained due to over-alkylation. One alternative method consists of the use of alcohols instead of halides as the alkylating agents. This transformation occurs via hydrogen transfer and generates water as only by-product. Numerous examples in literature show a wide range of metal-based catalysts that are able to perform this reaction, the majority requiring the assistance of a base or high temperature. Remarkably, not only the metal centre, but also the design of the ligand plays a crucial role. In our group, we have an extensive experience in the development of bifunctional catalysts that show high activity towards hydrogen autotransfer reactions.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;Here we present the synthesis of a new functionalized NHC−Ir (III) complex that catalyzes the alkylation of amines with alcohols affording selectively mono-alkylated products in quantitative yields, at room temperature, and in the absence of a base. This method has been applied to a variety of aromatic and even aliphatic amines. Mechanistic investigations have been performed, and a plausible mechanism will be discussed.

Base-free selective mono-N-alkylation of amines with alcohols catalyzed by a NHC−Ir(III) complex

ACS Spring 2022

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