This work describes the use of cheap, safe, and easy‐to‐handle hydrosilatrane as the reductant in direct reductive amination reactions. This efficient method enables a facile, metal‐free access to secondary and tertiary amines from a wide range of aldehydes and ketones, with the synthesis of tertiary amines requiring no additives at all. This reaction demonstrates excellent functional group tolerance, chemoselectivity, and scalability.magnified image

An efficient method for the reduction of ketones with 1‐hydrosilatrane is described. In the presence of a Lewis base activator, the resulting secondary alcohols are rapidly formed in good to excellent yields (20 examples, 71–99 % yields). The relative bulkiness of 1‐hydrosilatrane also enables the diastereoselective reduction of (–)‐menthone to (+)‐neomenthol, and the use of a chiral alkoxide activator can lead to the enantioselective reduction of prochiral ketones.

Hydrosilanes are cheap, readily available substrates, yet they do not see as extensive use for simple carbonyl reductions as borohydrides. Hydrosilane reducing agents broadly fall into one of two general categories: either a) they are easy to handle and require expensive and/or hazardous additives, or b) they are difficult and/or dangerous to handle. This work details the discovery of mild and functional group compatible condi-

The asymmetric direct reductive amination of prochiral ketones with aryl amines using 1-hydrosilatrane with a chiral Brønsted acid catalyst is reported. This is the first known example of chiral Brønsted acid-catalyzed asymmetric reductive amination using a silane as the hydride source. The reaction features a highly practical reducing reagent and proceeds efficiently at room temperature without a specialized reaction setup or equipment to exclude air or moisture. This method provides high conversion and enantiomeric excess up to 84% of the desired chiral secondary amines with minimal side products.

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A one-pot, direct reductive acetylation of aldehydes was achieved under mild conditions using 1-hydrosilatrane as a safe and easily accessible catalyst. Described herein is a facile synthesis that produces acylated primary alcohols that can serve as valuable building blocks for organic synthesis. The method has good functional group tolerance and works for a range of aryl aldehydes, with the notable exception of electron-rich arenes. A library of esters was isolated by flash chromatography in yields as high as 92%.

The cover picture shows artist Jesse Mai's imagination of the reduction of ketones to alcohols by 1‐hydrosilatrane. The accompanying work describes this mild method for reduction, which makes use of a cheap, safe, easy‐to‐handle, and environmentally friendly silane reducing reagent. The reported results include the conversion of a wide scope of ketones to alcohols, as well as demonstrations of stereoselective reductions: the diastereoselective reduction of (–)‐menthone to (+)‐neomenthol and the reduction of a prochiral ketone to an alcohol with an enantiomeric ratio of 87:13. Details are discussed in the Communication by M. J. Adler et al. on page 229 ff (DOI: http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201601256/abstract).