Enantioselective Rh-Catalyzed Hydrogenation of N-Formyl Dehydroamino Esters with Monodentate Phosphoramidite Ligands

Enantioselectivities up to >99% ee were achieved in the rhodium-catalyzed asymmetric hydrogenation of N-formyl dehydroamino esters using monodentate phosphoramidites as chiral ligands. The substrates were synthesized by condensation of methyl isocyanoacetate with a range of aldehydes and with cyclohexanone. A highly convenient multigram scale one step synthesis of methyl 2-(formamido)acrylate was developed. This compound was used in the synthesis of methyl 2-(formamido)cinnamate via a solvent free Heck reaction. Moreover, full conversion and >99% ee were obtained in 1 h in the hydrogenation of methyl 2-(formamido)acrylate with 0.2 mol % catalyst and 2 bar hydrogen pressure. The versatility of the formyl protection was established by its removal under mild conditions.