A chiral phosphine–olefin ligand derived from l-hydroxyproline and its use in the rhodium-catalyzed asymmetric 1,4-addition

A new chiral phosphine–olefin ligand (S)-1 has been designed and synthesized from l-hydroxyproline via a short reaction sequence. It was examined for its efficiency in the rhodium-catalyzed asymmetric addition of arylboronic acids and a phenylzinc reagent to cyclic α,β-unsaturated ketones, giving 1,4-addition products with high enantioselectivities.

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(S)-tert-Butyl 2-((diphenylphosphino)methyl)-2,5-dihydro-1H-pyrrole-1-carboxylateC12H26NO2P[α]D25 = −54 (c 1.0, CHCl3)Source of chirality: l-HydroxyprolineAbsolute configuration: (S)

(S)-tert-Butyl 2-((tosyloxy)methyl)-2,5-dihydro-1H-pyrrole-1-carboxylateC17H23NO5S[α]D25 = −117 (c 1.10, CHCl3)Source of chirality: l-HydroxyprolineAbsolute configuration: (S)