[1,2-Bis(phenylsulfinyl)ethane]palladium Acetate

Biographical Sketches

Christina McSweeney was born in Co.Cork, Ireland in 1986. She received a B.Sc. in Chemistry from the University College Cork in 2009, and is currently pursuing a Ph.D. under the supervision of Dr. Gerard P. McGlacken at University College Cork. Her current ­research is focused on the asymmetric α-alkylation of ketones.

Introduction

[1,2-Bis(phenylsulfinyl)ethane]palladium acetate 1, the ‘White catalyst’, was developed by M. Christina White and co-workers at the University of Illinois-Urbana. It has been shown to be an excellent, air-stable catalyst for the functionalization of allylic carbon centers. [¹] The bis-­sulfoxide palladium(II) catalyst participates in a number of important reactions including allylic C-H oxidation, [²] inter- and intramolecular alkylations, [³] sequential hydrocarbon functionalization, [4] macrolactonizations, [5] allylic C-H amination [6] and intermolecular oxidative Mizoroki-Heck reactions. [7] These useful transformations allow for rapid access to an array of synthetically useful moieties, such as allylic carboxylates, macrocycles, and amino alcohol deri­vatives.

Figure 1  White catalyst

Bis-sulfoxide palladium(II) acetate complex 1 is commercially available and can also be prepared via routine metal complexation with 1,2-bis(phenylmethanesulfinyl)ethane in dichloromethane at 40 ˚C. [8]

Abstracts

(A) The first documented use of this catalyst described an allylic C-H oxidation reaction for the preparation of allylic carboxylate compounds from substituted or unsubstituted alkenes and carboxylic acids. [²] These reactions can be performed in both an inter- or ­intramolecular fashion, the latter allowing access to highly functionalized, large-ring macrolactone products. [5]
(B) The catalyst was also used in the first catalytic direct alkylation of allylic C-H bonds via Pd(II) catalysis in the absence of base. [³] Shi and co-workers employed this methodology for the alkylation of 1,3-diketones. [³a] White and colleagues applied this methodology to furnish a wide range of linear (E),(R)-nitroarylpentenoates from aromatic and heteroaromatic allyl compounds alkylated with methyl nitroacetate. [³b] These products can serve as nucleophiles in asymmetric conjugate additions to generate enantiomerically enriched, unnatural R,R-disubstituted amino acid precursors.
(C) Compound 1 has also been reported to be highly effective in one-pot sequential allylic oxidation/C-H arylation reactions to ­afford the E-arylated allylic ester from the corresponding olefin, carboxylic acid, and arylboronic acid. [4]
(D) The catalyst has also been employed in the first general and stereoselective Pd(II)-catalyzed allylic C-H aminations, yielding functionalized oxazolidinones from N-tosylcarbamate precursors. [6a] This process is selective for the anti-oxazolidinone diastereomer, from which syn-1,2 amino alcohols are easily obtained. White also demonstrated the use of a more electron-deficient N-nosyl carbamate nucleophile, which furnishes vinyl syn-1,3-amino alcohol precursors from terminal olefins. [6b] Nahra et al. has demonstrated that when acetic acid instead of THF was used as solvent, under White’s conditions, a significant increase in the reaction rate is observed. [9] Catalyst 1 has also been used in intermolecular allylic aminations using O-methyl-N-tosylcarbamate as the amination reagent. [6c] Here ­the Pd(II)-bis(sulfoxide) operated in combination with a [CrIIICl(salen)] Lewis acid catalyst to obtain the linear allylic N-tosylcarbamate in good yield, regio- and diastereoselectivity.
(E) The White catalyst has been utilized in novel chelate-controlled intermolecular oxidative Heck reactions. [7] These reactions proceed with a wide range of non-resonance stabilized α-olefin substrates and organoboron reagents. The catalyst is sensitive to chelation effects from proximal oxygen and nitrogen moieties resulting in excellent regioselectivities for olefin insertion.
(F) Catalyst 1 has also been used by White to forge complex allylic esters by combining carboxylic acids and terminal olefins. [²c] This method employs mild conditions, such as low loadings of carboxylic acid and catalytic base, which enables broadening of the substrate scope. The method also facilitates the introduction of a oxygen functionality late in the synthetic sequence.

References

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• 2a Chen MS. White MC. J. Am. Chem. Soc.  2004,  126:  1346 
• 2b Chen MS. Prabagaran N. Labenz NA. White MC. J. Am. Chem. Soc.  2005,  127:  6970 
• 2c Vermeulen NA. Delcamp JH. White MC. J. Am. Chem. Soc.  2010,  132:  11323 
• 3a Lin S. Song C.-X. Cai G.-X. Wang W.-H. Shi Z.-J. J. Am. Chem. Soc.  2008,  130:  12901 
• 3b Young AJ. White MC. J. Am. Chem. Soc.  2008,  130:  14090 
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• 5b Stang EM. Christina WM. Nat. Chem.  2009,  1:  547 
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• 6b Rice GT. White MC. J. Am. Chem. Soc.  2009,  131:  11707 
• 6c Reed SA. Mazzotti AR. White MC. J. Am. Chem. Soc.  2009,  131:  11701 
• 7 Delcamp JH. Brucks AP. White MC. J. Am. Chem. Soc.  2008,  130:  11270 
• 8 Pettinari C. Pellei M. Cavicchio G. Crucianelli M. Panzeri W. Colapietro M. Cassetta A. Organometallics  1999,  18:  555 
• 9 Nahra F. Liron F. Prestat G. Mealli C. Messaoudi A. Poli G. Chem. Eur. J.  2009,  15:  11078