PdCl2/ DIOP

The earliest example of enantioface discrimination of a planar-stabilized carbanion, the second type of reaction, was the reaction of allylic phenyl ether and 2-acetyl-1 -tetralone aided by PdCl2(diop) and sodium phenoxide and resulted in up to 10% optical yield (203). 

Asymmetric hydrocyanation has now been achieved using norbornene and norbornadiene as substrates. The reduction of either [PdCl2(+)-DIOP] or PdCl2 in presence of (+)-DIOP led to a palladium(O) species formulated simply as [Pd(+)-DIOP]. This gave, in reaction (164), an optical yield of 30% for the 2-exo-cyanonorbornane formed. Norbornadiene with the same catalyst gave 2-exo-cyanonorborn-5-ene with an optical purity of 17%. When the ligand CHIRAPHOS (51) was used, the catalytic activity was greatly diminished.608,609 In addition to the review of the early work already mentioned, two more recent reviews of hydrocyanation have appeared.610,611... 

Table VI. Comparison Between Experiments and Forecast for the Prevailingly Carbonylated Unsaturated Carbon Atom and for Absolute Configuration in Asymmetric Hydrocarbalkoxylation by PdCl2/(-)DIOP on the...

SO far and their solution behavior was investigated by NMR. Both complexes were prepared by reduction of PdCl2(diop) in the presence of DIOP or ethylene, respectively. The low-temperature P NMR spectra of complex 1 show a pair of triplets, indicating that there are two pairs of magnetically inequivalent phosphorus nuclei in the complex. This observation is consistent with the tetrahedral geometry of Pd(0). 

Additional examples of palladium-catalyzed cross-couplings, in particular with allenylzinc compounds, can be found elsewhere [11, 15, 36]. A systematic study comparing several chiral palladium phosphine catalysts in the reaction of 4,4-di-methyl-1,2-pentadienylzinc chloride and iodobenzene revealed that an enantiomeric excess of only 25% was obtained from the best catalyst combination PdCl2 and (R,R)-DIOP [15]. The synthetic value of these transformations of donor-substituted allenes as precursors is documented by the preparation of a/l-unsaturatcd carbonyl... 

Substrate Hydroformylation RhH(CO) (PPh3)3 Hydroformylation [(—)-DIOP] PtCl2/SnCl2 Hydrocarboxylation PdCl2 ... 

Analysis of Reagent Purity for ((—)-(2f ,3f )-DIOP)PdCl2 crystal structure, H NMR, NMR, P NMR. Preparative Methods prepared from commercially available Pal-ladium(II) Chloride and (—)-(2R,3R)-(2,3-0-Isopropylidene)-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane in ether, or by treating a stoichiometric amount of (—)-(2R,3R)-DIOP in ethanol with Li2PdCU in water, or from (+)-(25,35)-DIOP and Pd(PhCN)2Cl2 in benzene or acetone. ... 

Methyl methacrylate has been hydromethoxycarbonylated with ((—)-(2/ ,3/ )-DIOP)PdCl2 as a catalyst to afford (5)-dimethyl succinate with excellent regioselectivity, but only modest enantiose-lectivity (eq 2). - ... 

Double Carbonylation of Aryl Halides. (DIOP)PdCl2 catalyzed the double carbonylation of phenyl iodide in the presence... 

Cross-Coupling of Halides. 4,4-Dimethyl-1-phenylpenta-1,2-diene has been prepared using a ((-)-(2f ,3f )-DIOP)PdCl2-catalyzed cross-coupling reaction, although low enantioselectivity was observed (eq 5). ... 

Other Pd Derivatives and Related Reactions. Other chiral palladium complexes, such as (DIOP)2Pd° or (DIOP)(alkene)Pd°, can be prepared from (DIOP)PdCl2. These catalysts have afforded low levels of asymmetric induction (10% ee) in the hydro-cyanation of norbomene derivatives. ... 

Oxirane Formation. The reaction of acetonyltributyltin with a-bromoacetophenone to yield 2-acetonyl-2-phenyloxirane has been investigated using ((-i-)-(2,S, 3,S )-DIOP)PdCl2 as a catalyst, but no asymmetric induction was observed. ... 

Carboxylic acids and their derivatives, esters, amides, anhydrides, and acyl halides, are formally synthesized from olefins, carbon monoxide, and compounds represented with HX where X- equals OR-, NR2-, etc (see Scheme 1). Considering that the chiral aldehydes obtained by asymmetric hydroformylation of viny-larenes are often oxidized in order to exhibit biological activities, asymmetric hydrocarboxylation and its related reactions naturally attract much attention. Unfortunately, however, as yet only less successful work has been reported on this subject than on hydroformylation. Palladium(II) is most commonly used for this purpose. Asymmetric hydrocarboxylation of olefins was first reported in 1973 by Pino using PdCl2 and (-)-DIOP [105]. Chiusoh reached 52% ee in the... 

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