| Abstract
| - The 2,5-dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometricallyand electronically characterized, and employed as ligand of Rh and Ru in some standardhydrogenation reactions of prostereogenic functionalized carbon−carbon and carbon−oxygen doublebonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOSand Me-DuPHOS display very similar geometries, while the electronic availability of the former ishigher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellentenantiomeric excesses (98.9−99.5%) in the hydrogenation of N-acetyl-α-enamino acids and reactionrates higher than those found when employing the analogous complexes of Me-DuPHOS.
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