Palladium complexes agents

Alkyl halides or alkyl sulfates, treated with the salts of sulfinic acids, give sulfones. A palladium catalyzed reaction with a chiral complexing agent led to sulfones with modest asymmetric induction. Alkyl sulfinates (R SO—OR) may be side products. Sulfonic acids themselves can be used, if DBU (p. 1337) is... 

A method for the accurate online ultratrace analysis of palladium in environmental samples (road dust and contaminated soil samples) by ICP-MS after separation of interferent cations by cation exchange chromatography was introduced by Hann and co-workers.80 Palladium was selectively adsorbed online onto a C18 microcolumn which had been reversibly loaded with a complexing agent... 

It is very well known that jr-allyl palladium complex 1, which is a key intermediate for the Tsuji-Trost type allylation, has an electrophilic character and reacts with nucleophiles to afford the corresponding allylation products. We discovered that bis 7r-allyl palladium complex 2 is nucleophilic and reacts with electophiles such as aldehydes [27] and imines [28-32] (Scheme 2, Structure 2). We have also shown that bis 7r-allyl palladium complex 2 can act as an amphiphilic catalytic allylating agent it reacts with both nucleophilic and electrophilic carbons at once to produce double allylation products [33]. These complexes incorporate two allyl moieties that can bind with different hapticity to palladium (Scheme 3). The different complexes may interconvert by ligand coordination. The complexes 2a, 2b and 2c are called as r]3,r]3-bisallypalladium complex (also called bis-jr-allylpalladium complex), r)l,r)3-bis(allyl)palladium complex, -bis(allyl)palladium complex, respectively. Bis zr-allyl palladium complex 2 can easily be generated by reaction of mono-allylpalladium complex 1 and allylmetal species 3 (Scheme 4) [33-36]. Because of the unique catalytic activities of the bis zr-allyl palladium complex 2, a number of interesting cascade reactions appeared in the literature. The subject of the present chapter is to review some recent synthetic and mechanistic aspects of the interesting palladium catalyzed cascade reactions which in-... 

Enantioselective fluorination is commonly conducted with chiral agents such as quinine-based [N-F]+ compounds, and these have been successfully utilised in ionic liquids.115,161 Very good yields and selectivities have been obtained in the enantioselective fluorination of /Nkctoesters catalysed by the chiral palladium complex 57, see Scheme 9.2. l l Depending on the substrate employed, substantial acceleration of the reaction rate relative to that in ethanol was observed with yields and selectivities comparable to those obtained in water or ethanol. The reaction rate was found to depend on both the length of the alkyl substituent of the imidazolium cation as, well as on the type of anion present, whereas the selectivity was not affected by such variations. The products were extracted from the ionic liquid phase with diethyl ether, and in that manner catalytic activity was maintained for up to ten cycles. 

Ethylene (tert-phosphine) complexes of zero-valent nickeP and platinum have been known for years. Analogous palladium complexes can be synthesized along the same lines as those reported for the nickel compounds, using ethoxy-diethylaluminum(III) as the reducing agent in the presence of ethylene. These palladium-ethylene complexes may serve as starting materials for oxidative addition reactions, since the ethylene ligand is loosely bonded. ... 

Aryl, vinyl, and benzyl halides are catalytically carbonylated by CO generated in situ from chloroform and aqueous alkali, in the presence of phosphine-palladium complexes such as PdCl2(PPh3)3. The biphasic reactions do not require a PT agent, they occur at r.t., and they afford the corresponding carboxylic acids in up to 92% yield. Labeling experiments with CHCb showed that the source of the Cl unit in the carbonylation is chloroform... 

Zim and Buchwald synthesized the palladacyclic phosphine complex 44 based on their ligand P(Bu-f)2(o-biphenyl) 13 (equation 46)157. This air- and moisture-stable palladium complex is a convenient one-component precatalyst for animation of aryl chlorides when combined with sodium tert-butoxide or sodium methoxide. For coupling of anilines, the addition of NEt3, which is possibly acting as the reducing agent to produce Pd(0), is necessary. 

Bicyclic systems with a vinylcyclopropane fragment reacted in a similar way. The mechanism postulated for these reactions involves the formation of a zwitterionic palladium complex in which the three-membered ring has already been opened. Hydrogen abstraction from the C-H acidic agent gives a carbanion which adds to the -aIlyl ligand of the palladium with removal of the metal. ° ... 

The arylation reaction of primary and secondary amines has been investigated using nickel or palladium complexes as catalysts, and bromo- or chloroarenes as arylating agents. Among the complexes tested, the more efficient catalyst is the bis (bipyridyl) nickel (II) bromide, bipy2NiBr2, which affords for example high yields in the arylation of allylamine with /n-bromotrifluoromethylbenzene. The reduction of the haloarene, sometimes observed with the nickel complexes, becomes predominant with palladium catalysts whatever the complex used. 

---