Direct, Enantioselective Iridium-Catalyzed Allylic Amination of Racemic Allylic Alcohols

Marc Lafrance, Markus Roggen, and Erick M. Carreira Angew. Chem. Int. Ed.

Carreira’s group report a method for the direct enantioselective amination of racemic secondary allylic alcohols. Metal-catalysed allylic substitution is usually carried out with ester, carbonate or phosphate leaving groups; very few examples using the hydroxyl leaving group are reported. The group employ sulfamic acid as a surrogate for ammonia, allowing access to primary amines without over-substitution.

Optimisation of reaction conditions found that phosphoramidite ligand L provides good reactivity and selectivity. It’s worth noting that without the conjugating alkene group between the aromatic rings of the ligand, reactivity drops off entirely. They suggest that this alkene acts as a donor group in the reaction mechanism and promotes reactivity through exchange with the substrate at the iridium centre.

The amine products were isolated after an in situ protection. They showed that isolation as the Bz-, Ts, Fmoc-protected and HCl salt derivatives is feasible and that a wide variety of substitution on the aromatic ring is tolerated. Alkyl substitution is also well tolerated, enantioselectivity only begins to break down with more flexible substituents.

DOI: 10.1002/anie.201108287

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