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Rhodacarborane complexes with a triphenylphosphonium substituent as efficient catalysts for on-water transfer hydrogenation of carbonyl compounds
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DOI:10.1039/d6dt00999a.png)
Abstract
En 中文
Two isomeric rhodacarborane chloride complexes [1,8-Bn-2-2,2-Cl-2-X-PPh3-2,1,8-closo-RhC2B9H8](2) (X = 7 and 11) were synthesized. One of them (X = 7) exhibits high catalytic activity in the on-water reduction of aromatic and aliphatic aldehydes and ketones with ammonium formate to the corresponding alcohols with a 0.2 mol% loading. The enantiopure form of a planar chiral catalyst was obtained via isolation of a cyclometallated complex with (S)-proline. The enantiopure form of the catalyst affords alcohols with enantiomeric excess when prochiral ketones are used in the reaction. The same catalyst is active in the Oppenauer-type oxidation of (+/-)-1-phenylethanol with acetone in the presence of K2CO3. The transfer hydrogenation is accompanied by in situ reversible cyclometallation of the catalytic species engaging the ortho-CH bonds of PPh3.
Keywords:
OPPENAUER-TYPE OXIDATION
HALF-SANDWICH COMPLEXES
MOLECULAR-STRUCTURE
THERMAL REARRANGEMENT
ALKENE ISOMERIZATION
GAMMA-VALEROLACTONE
REACTIVITY
METAL
LIGAND
METALLACARBORANES
Journal
IF:
3.3
Papers:
3.3W
Citations:
7.5W
