Furanoside diphosphinite ligands

Furanoside diphosphinite ligands 10 and 11 (Fig. 11) were applied in the Ir-catalyzed asymmetric hydrogenation of several dehydroaminoacid derivatives [25]. The best enantioselectivities (ee s up to 78%) were obtained in the reduction of methyl W-acetamidoacrylate with ligand 10. These results using the lr/10-11 catalysts precursor show that enantiomeric excesses are strongly dependent on the absolute configuration of the C-3 stereocenter of the carbohydrate backbone. The best enantioselectivity were therefore obtained with ligand 10 with an... 

Fig. 11 Summary of the best results obtained in the Ir-catalyzed hydrogenation using furanoside diphosphinite ligands 10 and 11...

Later, furanoside diphosphinite ligands 12, but with C2-symmetry, provided enantioselectivities up to 70% in the asymmetric hydrogenation of several N-arylimines (Fig. 12) [26]. The electronic effect of the ligand on enantioselectivity is considerable. Results were best when electron-donating groups are present on the phenyl rings (ligand 12b). On the other hand, the use of additives was detrimental to both conversion and enantioselectivity. 

The furanoside phosphite-phosphinite ligand 13, related to the previously diphosphinite ligands 12, was also applied to the asymmetric hydrogenation of N-arylimines, increasing the enantioselectivities up to 76% (Fig. 13) [26]. Precursors based on cationic [Ir(cod)2]BF4 provided better yields and enantioselectivities than... 

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See also in sourсe #XX -- [ ]

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