Asymmetric Transfer Hydrogenation of Hemisquaramides: Access to Enantioenriched α-Hydroxy-3-aminocyclobutenone Derivatives

The asymmetric transfer hydrogenation (ATH) of readily available hemisquaramides, catalyzed by a tethered Noyori-Ikariya-type complex, proceeds with complete chemoselectivity and leads after acylation to derivatives of enantioenriched α-hydroxy-3-aminocyclobutenones, generally in excellent yields and high enantiomeric purities. This work contributes to expanding the scope of ATH to new classes of strained substrates and underscores the influence of reaction conditions on the enantioselectivity.