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Synlett 2006(2): 329-330  
DOI: 10.1055/s-2005-923609
SPOTLIGHT
© Georg Thieme Verlag Stuttgart · New York

Palladium(II) Acetate [Pd(OAc)2]: A Versatile Catalyst

Rakesh Kumar Vats*
Lab. H-102, Department of Pharmaceutical Technology, National Institute of Pharmaceutical Education and Research (NIPER), ­Sector 67, Phase 10, S.A.S. Nagar (Mohali), Punjab-160062, India
e-Mail: rakeshvats@chemist.com;
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Publication History

Publication Date:
23 December 2005 (online)

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Introduction

Palladium(II) acetate [Pd(OAc)2] [CAS: 3375-31-3] is a commercially available reagent, which is stable and soluble in organic solvents. It has a melting point of 195 °C (dec.). It can be prepared from metallic palladium by dissolving in acetic acid containing nitric acid. It may contain nitrate anion as impurity. Pd(OAc)2 is purified by dissolving it in hot benzene and concentrating the benzene solution after removing the insoluble part. Pure Pd(OAc)2 can be obtained as needle-like crystals by recrystallization.

Palladium(II) acetate is used for oxidative addition, insertion, transmetalation and reductive elimination reactions. It is used for allylic oxidation (acetoxylation), e.g. oxidation of cyclohexene to 2-acetoxycyclohexene. Unsaturated aldehydes can be elongated by one carbon atom. Silyl enols undergo transmetalation followed by intramolecular alkene insertion and β-elimination. Acetoxybenzene is prepared by reaction of benzene with Pd(OAc)2. This is a useful method for phenol production from benzene. Pd(OAc)2 is widely used in the presence of phosphine ligand and as a base in Heck reaction, for coupling aryl or vinyl halides with alkenes. [1] In the presence of TBAB, it catalyses direct homocoupling of aryl halides. [2] It is also used to improve Wacker oxidation of terminal alkenes to 2-alkanones with p-benzoquinone, which improves the reaction rate 50-fold. [3] It is efficient in ligandless Suzuki cross-coupling of aryl boronic acids with aryl iodides. [4] A stoichiometric quantity is required in Buchwald-Hartwig reaction of C-N bond formation. Selective reduction of alkynes is catalyzed by Pd(OAc)2 with NaOMe [5] and reduction of aryl/enol triflates by this catalyst is reported. [6] Pd(OAc)2 was microencapsulated in polyurea for making it reusable and recoverable catalyst for hydrogenation. [7]