Bis(phosphite) Ligands with Distal Regulation: Application in Rhodium‐mediated Asymmetric Hydroformylations

Abstract

Small amounts of achiral polyether binders are employed to enhance the enantioselectivity of the hydroformylation of an array of diversely substituted substrates (increase of up to 62% ee for vinyl acetate) mediated by chiral rhodium complexes derived from the α,ω-bis(phosphite)-polyether ligands 1. To the best of our knowledge, this study represents an unprecedented successful example of the positive regulation of enantioselectivity in hydroformylations.

Synthesis of Elusive Chloropnictenium Ions

“…The introduction of a macrocyclic crown ether skeleton with selective binding properties into the catalyst structure is expected to result in distinctive catalytic performance involving a host–guest recognition process 3. However, to the best of our knowledge, the application of metallacrown ethers as catalysts has not been widely studied,2d,2f–2l especially the use of chiral metallacrown ethers in asymmetric catalysis 2g,2l. Recently, we have developed a new class of readily available and tunable bis(phosphite) ligands with an oligo(ethylene glycol) backbone, and a pronounced enhancement of enantioselectivity was achieved in the rhodium‐catalyzed asymmetric hydrogenation of α‐dehydroamino acid esters by the addition of NaBArF {BArF = [3,5‐(CF 3 ) 2 C 6 H 3 ] 4 B} 2g.…”

Podand‐Based Dimeric Chromium(III)–Salen Complex for Asymmetric Henry Reaction: Cooperative Catalysis Promoted by Complexation of Alkali Metal Ions

“…The complexation of an alkali metal ion has shown remarkable effects on both catalytic activity and enantioselectivity in the asymmetric hydrogenation of α‐dehydroamino acid esters. Later, Vidal‐Ferran and coworkers reported a similar chiral bis(phosphite)‐containing metallacrown ether catalyst, showing tunable catalytic properties in the Rh‐catalyzed asymmetric hydroformylation of terminal olefins 8b…”

Supramolecularly fine-regulated enantioselective catalysts

“…The supramolecularly regulated -bisphosphite was successfully applied to the AHF of terminal alkenes with highly positive regulation effects on the enantioselectivity (increases of up to 62% ee for vinyl acetate). 26 Further optimization studies towards the optimal supramolecularly regulated ligand for this chemistry (i.e.…”