Reduction of amides to amines is a synthetically important reaction, but typically relies on metal hydride reductants such as LiAlH4 or NaBH4 that are non-selective, highly water sensitive, and can be challenging for work on larger scales. New catalytic approaches reduction of amides to amines can provide alternative pathways that employ more efficient regents. In this context, organosilanes are potentially advantageous reductants because their kinetic stability in air, the earth abundance of silicon, and the potential for varying the substituents to control reactivity. Moreover, the siloxane byproducts are readily handled and potentially recycled. With this idea in mind, we have studied the cationic Rh(I) cyclooctadiene complex [XantphosRh(h2-C8H12)]BArF4 as a catalyst for the reduction of tertiary amides to amines using phenylsilane as the reductant. Many amides are reduced in less than 15 minutes at 60 °C with 1 mol % catalyst loading. This system can also tolerate functionality, including bromo, nitro and azo groups. Secondary amides are more challenging substrates due to a competitive alkylation process that gives a mixture of primary, secondary and tertiary amine products. Strategies to reduce secondary amides to secondary amines to avoid this side reaction will be presented.

Rhodium-catalyzed reduction of secondary and tertiary amides to amines using phenylsilane

249th National Meeting (2015)

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