Thermally Stable P‐Chiral Supramolecular Phosphines, their Self‐Assembly and Implication in Rh‐Catalyzed Asymmetric Hydrogenation
P‐chiral supramolecular phosphine ligands are crucial for asymmetric transformations, but their synthesis is tedious. We report a one‐step synthesis of thermally stable P‐chiral supramolecular phosphines and their performance in the asymmetric hydrogenation of functionalized alkenes. A rational desi...
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Veröffentlicht in: | Chemistry : a European journal 2024-08, Vol.30 (45), p.e202401077-n/a |
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Zusammenfassung: | P‐chiral supramolecular phosphine ligands are crucial for asymmetric transformations, but their synthesis is tedious. We report a one‐step synthesis of thermally stable P‐chiral supramolecular phosphines and their performance in the asymmetric hydrogenation of functionalized alkenes. A rational designing and synthesis of (R, R)‐QuinoxP* ligated palladium complex (Pd‐2) in excellent yield is reported. This Pd‐2 catalyzed a direct P−C coupling of 2,3‐dihydro‐1‐H‐phosphindole (A1)/1,2,3,4‐tetrahydrophosphindoline (A2) with 1‐(3‐iodophenyl)urea (B1)/2‐iodo /6‐hydroxy pyridine (B2) and,produced corresponding ligands L1–L3. The P−C coupling between A1 and B2 produced 6‐(2,3‐dihydro‐1H‐phosphindol‐1‐yl)pyridine‐2(1H)‐one (L2) with an excellent enantiomeric excess of up to 99 %. L2 was found to be remarkably stable even at 150 °C and did not oxidize/hydrolyze for at least 24 hours in open air. Such thermal stability and an impediment to oxidation are unprecedented. L2 self‐assembled and produced L2−C1 (Pt), L2−C2(Pd), and L2−C3(Rh) assemblies. The utility of the self‐assembled P‐chiral ligand was demonstrated in the Rh‐catalyzed asymmetric hydrogenation (AH) of functionalized olefins. The L2−C3 catalyzed AH of functionalized alkenes and delivered chiral products with excellent enantioselectivity of >99 %. A small library of 16 substrates was subjected to AH using L2−C3 to produce chiral compounds with excellent conversion and ee.
Synthesis of thermally stable P‐chiral supramolecular phosphines with enantiomeric excess of up to 99 % is reported. These phosphines are stable up to 150 °C and can be handled in air for a few hours. They can self‐assemble on metals such as Pt, Pd, Rh to produce chiral catalysts. The self‐assembled Rh‐complex catalyzes the asymmetric hydrogenation of functionalized alkenes to yield chiral compound with an ee of 99 % and near quantitative conversion. |
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ISSN: | 0947-6539 1521-3765 1521-3765 |
DOI: | 10.1002/chem.202401077 |