In this Minireview, the synthesis of amines by the amination of alcohols, by means of the so‐called borrowing hydrogen methodology, is presented. Compared to other synthetic methodologies for the synthesis of amines, these transformations are highly attractive because often alcohols are readily available starting materials, some of them on a large scale from renewable sources. In addition, the amination of alcohols produces water as the only by‐product, which makes the process potentially environmentally benign. Already today, lower alkyl amines are produced in bulk by the chemical industry with this synthetic method. In particular, the recent progress applying organometallic catalysts based on iridium, ruthenium, and other metals will be discussed. Notable recent achievements include the conversion of challenging substrates such as diols, the development of recyclable catalysts, milder reaction temperatures, and the direct alkylation of ammonia or its equivalents with alcohols.
Atom efficiency and selectivity are the key features of the first homogeneously catalyzed amination of secondary alcohols with ammonia to give the corresponding primary amines (see scheme). This novel amination method relies on the commercially available catalyst [Ru3(CO)12]/cataCXium PCy and does not require any additional source of hydrogen.
A novel and convenient protocol for the catalytic hydrogen-deuterium exchange of biologically active tertiary amines utilizing the borrowing hydrogen methodology has been developed. In the presence of the readily available Shvo catalyst, excellent chemoselectivity toward α- and β-protons with respect to the nitrogen atom as well as high degree of deuterium incorporation and functional group tolerance is achieved. This allowed for the deuteration of complex pharmaceutically interesting substrates, including examples for actual marketed drug compounds. Notably, this method constitutes a powerful tool for the generation of valuable internal standard materials for LC-MS/MS analyses highly demanded for various life-science applications.
Alcohols for alkylation! The first homogeneous ‐catalyzed N‐alkylations of indoles with aliphatic alcohols proceed under transfer hydrogenation conditions. By the use of the Shvo catalyst and p‐toluenesulfonic acid (PTSA) this atom‐efficient reaction occurs highly selectively with water formed as the only byproduct (see scheme).
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