Iridium-catalysed hydroamination of internal homoallylic amines.

An Ir-catalysed regioselective hydroamination of internal homoallylic amines is reported. Both cyclic and acyclic internal olefins undergo directed hydroamination reactions with both aromatic and cyclic aliphatic amines to afford a variety of 1,4-diamines in fair to excellent yields. Diastereoselectivity and mechanistic investigations support that for cyclic substrates the reactions are proceeding via trans-aminoiridation to form a 5-membered metalacyclic intermediate.

Current Progress in the Chemoenzymatic Synthesis of Natural Products.

Natural products, with their array of structural complexity, diversity, and biological activity, have inspired generations of chemists and driven the advancement of techniques in their total syntheses. The field of natural product synthesis continuously evolves through the development of methodologies to improve stereoselectivity, yield, scalability, substrate scope, late-stage functionalization, and/or enable novel reactions. One of the more interesting and unique techniques to emerge in the last thirty years is the use of chemoenzymatic reactions in the synthesis of natural products. This review highlights some of the recent examples and progress in the chemoenzymatic synthesis of natural products from 2019-2022.

Synthesis of Unsymmetrical Vicinal Diamines via Directed Hydroamination.

Vicinal diamines are a common motif found in biologically active molecules. The hydroamination of allyl amine derivatives is a powerful approach for the synthesis of substituted 1,2-diamines. Herein, the rhodium-catalyzed hydroamination of primary and secondary allylic amines using diverse amine nucleophiles, including primary, secondary, acyclic, and cyclic aliphatic amines to access a wide range of unsymmetrical vicinal diamines, is presented. The utility of this methodology is further demonstrated through the rapid synthesis of several bioactive molecules and analogs.

Rhodium-/Iridium-Catalyzed Hydroamination for the Synthesis of 1,2-, 1,3-, or 1,4-Diamines.

An Ir-catalyzed regioselective hydroamination of allyl amines using aryl amines and catalyst-controlled regiodivergent hydroamination of allylic and homoallylic amines with aniline nucleophiles are reported. The directed hydroamination reactions afford a variety of 1,2-, 1,3-, and 1,4-diamines in good to excellent yields and high regio- and chemoselectivities. Mechanistic investigations suggests that the reactions are proceeding through an oxidative addition into the ArHN-H bond and that the observed regioselectivity is due to the selective formation of a 5- or 6-membered metalacyclic intermediate, depending on the catalyst employed.

Rhodium-Catalyzed Asymmetric Hydroamination of Allyl Amines.

A Rh-catalyzed enantioselective hydroamination of allylamines using a chiral BIPHEP-type ligand is reported. Enantioenriched 1,2-diamines are formed in good yields and with excellent enantioselectivities. A diverse array of nucleophiles and amine directing groups are demonstrated, including deprotectable motifs. Finally, the methodology was demonstrated toward the rapid synthesis of 2-methyl-moclobemide.

Anti-Markovnikov Hydroamination of Homoallylic Amines.

The development of an anti-Markovnikov-selective hydroamination of unactivated alkenes is a significant challenge in organometallic chemistry. Herein, we present the rhodium-catalyzed anti-Markovnikov-selective hydroamination of homoallylic amines. The proximal Lewis basic amine serves to promote reactivity and enforce regioselectivity through the formation of the favored metallacycle, thus over-riding the inherent reactivity of the alkene. The scope of both the amine nucleophiles and homoallylic amines that participate in the reaction is demonstrated.