Palladium(II) acetate [Pd(OAc)2]: A versatile catalyst

Abstract

(A) Oxygenation of unactivated sp3 C-H bonds can be achieved with Pd(OAc)2 and PhI(OAc)2 as oxidant. The unactivated sp3 C-H bonds of both oxime and pyridine substrates undergo highly regio- and chemoselective oxygenation. (Diagram presented) (B) Preparation of benzolactams by Pd(OAc)2 catalyzes direct aromatic carbonylation in an atmosphere of CO gas with air. (Diagram presented) (C) Distannylation of strained C-C triple bonds is catalyzed by Pd(OAc)2. Oxidative addition of a distannane to a palladium complex occurs during the distannylation of in situ generated arynes with distannanes in the presence of catalytic amount of Pd/tert-octyl isocyanide (t-OcNC) complex to give 1,2-distannylarenes in moderate to high yields. The synthesis of highly substituted 1,3-butadienes by arylation of internal alkynes can be achieved with the help of Pd(OAc) 2. (Diagram presented) (D) Pd(OAc)2-catalyzed functionalization of indoles with 2-acetoxy methyl substituted electron deficient alkenes was performed under neutral conditions. This protocol is very efficient and may open new area for functionalization of indoles. Pd(OAc) 2-catalyzed tandem Heck and aldol reaction between 2-bromobenzaldehyde and functionalized alkenes leads to naphthalene. (Diagram presented) (E) Pd(OAc)2 catalyzes multiple arylation via successive C-C and C-H bond cleavages. These unprecendented reactions seems to provide useful information for designing new catalytic cycles that occur via C-C and C-H cleavages. (Diagram presented) (F) The asymmetric desymmetrization of prochiral meso compounds represents a powerful strategy for the expedient synthesis of two or more contiguous stereogenic centres in one operation. Pd(OAc)2 provides the desired keto acid in good yield and enantiomeric excess. (Diagram presented) (G) Pd(OAc)2 in pyridine is developed as an effective catalyst for highly regioselective hydroselenation of alkynes. (Diagram presented) (H) The α-arylation of methanesulfonamides using phosphine ligands and NaOt-Bu as a base was also achieved with Pd(OAc)2. (Diagram presented) © Georg Thieme Verlag Stuttgart.