Dendritic phosphoramidite ligands for Rh-catalyzed [2+2+2] cycloaddition reactions: unprecedented enhancement of enantiodiscrimination

Abstract

Phosphorus dendrimers containing terminal phosphoramidite ligands have been found to be highly effective and recoverable catalysts for the rhodium(I) catalyzed [2+2+2] cycloaddition reactions. A strong positive dendritic effect is observed both in the activity and enantiodiscrimination leading to axially chiral biaryl compounds.

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

“…80). 386 The phosphoramidite ligands for Rh complexation were also immobilized onto the peripheral groups of PPH dendrimers (331-Gn). An enhancement in both yield and enantioselectivity through a positive dendrimer effect was observed.…”

Phosphorus dendrimers as supports of transition metal catalysts

“…14). This unprecedented enhancement of the stereoselectivity induced by the dendrimers might be due to the large number of chiral ligands in close proximity, as a branch model (two phosphoramidite complexes) was not more efficient than the monomer [54]. …”

“…The first step was the condensation with butylamine, followed by the reduction of the imine functions with NaBH 4 . The last step was the reaction of the secondary amine with the chlorophosphite derived from (S)-BINOL, affording dendrimers 14-Gc n (n = 1-3) (Scheme 13) [54]. The complexes obtained by reaction of the dendrimers 14-Gc n with [Rh(C 2 H 4 ) 2 Cl] 2 were used in particular for catalyzing [2+2+2] cycloaddition reactions between N-tosyl 1,6-diyne and phenylacetylene.…”

Phosphorhydrazones as Useful Building Blocks for Special Architectures: Macrocycles and Dendrimers

“…The differences observed are an illustration of the so‐called dendrimer (or dendritic) effect . In another example, the enantiodiscrimination has been largely increased for [2+2+2] cycloaddition reactions catalyzed with dendritic phosphoramidite complexes of ruthenium; the corresponding monomeric complex induced no enantioselectivity.…”