(2R,3R) or (-)

[63598-08-3]  · C31H32Cl2O2P2Pd  · Dichloro[2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane]palladium(II)  · (MW 675.87) (2S,3S) or (+)


(chiral catalyst used in asymmetric hydrocarboxylation1 or hydroalkoxycarbonylation reactions,2 allylation of b-diketones or b-keto esters,3 double carbonylation,4 cross-coupling reactions,5 preparation of optically active Pd0 derivatives and their subsequent reactions6)

Alternate Name: (DIOP)PdCl2.

Physical Data: crystalline pale yellow solid; ((-)-(2R,3R)-DIOP)PdCl2, [a]D -7.9° (CHCl3, c 1.0);6b mp 278-279 °C (dec).7b

Solubility: sol dichloromethane; insol heptane.

Analysis of Reagent Purity: for ((-)-(2R,3R)-DIOP)PdCl2: crystal structure,7a 1H NMR,6b,7b 13C NMR,6b 31P NMR.6b

Preparative Methods: prepared from commercially available Palladium(II) Chloride and (-)-(2R,3R)-(2,3-O-Isopropylidene)-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane in ether,7a or by treating a stoichiometric amount of (-)-(2R,3R)-DIOP in ethanol with Li2PdCl4 in water,5 or from (+)-(2S,3S)-DIOP and Pd(PhCN)2Cl2 in benzene6b or acetone.3c

Handling, Storage, and Precautions: relatively stable to air oxidation.

Asymmetric Hydrocarboxylation.

The title reagent was used in the first example of an asymmetric hydrocarboxylation (eq 1).1a,1c With the a-methylstyrene, the straight chain isomer was formed. The regiospecificity was much less pronounced, however, for other alkenic substrates.1b The influence of some reaction variables on the reaction shown in eq 1 was studied. For example, the presence of a solvent such as THF or benzene, the alcohol source, the effect of CO pressure, the effect of substitution on the phenyl ring, the PdCl2/DIOP molar ratio, or the presence of PPh3 along with DIOP, were varied to improve the optical yield.1c-e

Methyl methacrylate has been hydromethoxycarbonylated with ((-)-(2R,3R)-DIOP)PdCl2 as a catalyst to afford (S)-dimethyl succinate with excellent regioselectivity, but only modest enantioselectivity (eq 2).2a,2b

Asymmetric Allylic Alkylation.

In early investigations of Pd-mediated allylations of alkenes and allylic acetates, Trost and his co-workers used (+)-(2S,3S)-DIOP along with PdCl2 or Pd(PPh3)4 and obtained optical yields in the range of 12-46%.3a,3b In the allylation of b-diketones or b-keto esters using allyl phenyl ether or allylic esters, use of the title reagent as a chiral catalyst afforded allylated compounds in good yields, but with low enantioselectivity (eq 3).3c

Double Carbonylation of Aryl Halides.

(DIOP)PdCl2 catalyzed the double carbonylation of phenyl iodide in the presence of diethylamine to afford the a-ketoamide in a very good yield along with a minor amount of the benzamide derivative (eq 4).4

Cross-Coupling of Halides.

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

Other Pd0 Derivatives and Related Reactions.

Other chiral palladium complexes, such as (DIOP)2Pd0 or (DIOP)(alkene)Pd0, can be prepared from (DIOP)PdCl2.6a,6d These catalysts have afforded low levels of asymmetric induction (10% ee) in the hydrocyanation of norbornene derivatives.6b,6c

Oxirane Formation.

The reaction of acetonyltributyltin with a-bromoacetophenone to yield 2-acetonyl-2-phenyloxirane has been investigated using ((+)-(2S,3S)-DIOP)PdCl2 as a catalyst, but no asymmetric induction was observed.8

1. (a) Botteghi, C.; Consiglio, G.; Pino, P. C 1973, 27, 477. (b) Consiglio, G.; Marchetti, M. C 1976, 30, 26. (c) Consiglio, G.; Pino, P. C 1976, 30, 193. (d) Consiglio, G. JOM 1977, 132, C26. (e) Consiglio, G.; Roncetti, L. Chirality 1991, 3, 341.
2. (a) Consiglio, G.; Kollár, L.; Kölliker, R. JOM 1990, 396, 375. (b) Consiglio, G.; Nefkens, S.; Pisano, C.; Wenzinger, F. HCA 1991, 74, 323
3. (a) Trost, B. M.; Dietsche, T. J. JACS 1973, 95, 8200. (b) Trost, B. M.; Strege, P. E. JACS 1977, 99, 1649. (c) Fiaud, J. C.; Gournay, A. H.; Larcheveque, M.; Kagan, H. B. JOM 1978, 154, 175.
4. Kobayashi, T.; Tanaka, M. JOM 1982, 233, C64.
5. De Graaf, W.; Boersma, J.; Van Koten, G.; Elsevier, C. J. JOM 1989, 378, 115.
6. (a) Brown, K.; Chaloner, P. A. JOM 1981, 217, C25. (b) Elmes, P. S.; Jackson, W. R. AJC 1982, 35, 2041. (c) Hodgson, M.; Parker, D.; Taylor, R. J.; Ferguson, G. OM 1988, 7, 1761. (d) Hodgson, M.; Parker, D.; Taylor, R. J.; Ferguson, G. CC 1987, 1309.
7. (a) Gramlich, V.; Consiglio, G. HCA 1979, 62, 1016. (b) Chaloner, P. A. JOM 1984, 266, 191.
8. Pri-Bar, I.; Pearlman, P. S.; Stille, J. K. JOC 1983, 48, 4629.

Ronan Guével

The Ohio State University, Columbus, OH, USA

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