Alkylation palladium chloride

With palladium chloride catalyst, carbon monoxide, and an alcohol the labile hydroxyl is alkylated during carbonylation (199). 

Alkyl iodides, benzyl chlorides, benzyl bromides, and adamantyl bromides and iodides undergo reduction with triethylsilane/palladium chloride.195 The reduction of a /3-chloro ether occurs in excellent yield with this system (Eq. 56).195... 

C(l) in 355 is in the oxidation state of an aldehyde or a ketone in 1-alkylated products. The necessary solvolytic attack of the enol carbamate double bond requires substoichio-metric amounts of a catalyst such as mercuric acetate or palladium chloride and one equivalent of acid (e.g. methanesulphonic acid) for binding the liberated diisopropylamine. 

Two metal halides have been found to react with olefins by what appears to be insertion reaction. Palladium chloride and mercury chloride both will add to olefins. The palladium alkyls canot be isolated, but they go on to products which can be accounted for by an initial addition. 

A number of methods for the preparation of vinyl and allyl sulfones are available [1U9, 110], and the syntheses of vinyl sulfones from alkenes has been reviewed [116]. A simple one-step procedure of wide applicability makes use of a palladium-catalysed cross-coupling reaction between aryl and alkyl sulfonyl chlorides and substituted vinyl and allyl stannanes... 

Diphenyl selenide is a colourless, strongly refractive oil, B.pt. 167° C. at 16-5 mm. insoluble in water but miscible with alcohol or ether in all proportions. It has a faint odour, and a density of 1 3712 at 0° C., 1 3561 at 15 2° C., and 1 350 at 20° C. With cold bromine in ether solution it yields the dibromide. Diphenyl selenide, unlike dimethyl selenide, does not combine with alkyl iodides, and in this respect it resembles diphenyl sulphide.2 When heated nearly to its boiling-point with sulphur it gives diphenyl sulphide, the reaction being practically quantitative at 300° C.3 With palladium chloride it forms the complex PdCl2.2(C6H5)2Se, orange-red needles, M.pt. 181° to 182° C.4... 

Terminal monoalkenes were alkylated by stabilized carbanions (p a 10-18) in the presence of 1 equiv. of palladium chloride and 2 equiv. of triethylamine, at low temperatures (Scheme l).1 The resulting unstable hydride eliminate to give the alkene (path b), or treated with carbon monoxide and methanol to produce the ester (path c).2 As was the case with heteroatom nucleophiles, attack at the more substituted alkene position predominated, and internal alkenes underwent alkylation in much lower (=30%) yield. In the absence of triethylamine, the yields were very low (1-2%) and reduction of the metal by the carbanion became the major process. Presumably, the tertiary amine ligand prevented attack of the carbanion at the metal, directing it instead to the coordinated alkene. The regiochemistry (predominant attack at the more sub-... 

When the reactions were carried out in acetonitrile with palladium acetate or in methanol with palladium chloride/triethylamine with other phenyl alkyl telluriums, the yields of alkanecarboxylic acids never exceeded 8%l. 

Palladium coordinates to one face of the diene promoting intramolecular attack by the alcohol on the opposite face. The resulting <7-alkyl palladium can form a 71-allyl complex with the palladium on the lower face simply by sliding along to interact with the double bond. Nucleophilic attack of chloride from the lithium salt then proceeds in the usual way on the face opposite palladium. The overall addition to the diene is therefore cis. 

The conclusions are (1) oxidative addition is efficient with Ni and Pd (2) the Pd insertion products are more stable than the Ni analogs, but in no case are the non-ligand-stabilized species isolable (3) decomposition of the insertion products first proceeds by CO elimination with formation of the alkyl- or aryl palladium chloride, which if unstable can decompose to a variety of products including PdCl2, Pd, alkyl or aryl chloride, and coupling products. 

Olefin isomerization has been widely studied, mainly because it is a convenient tool for unravelling basic mechanisms involved in the interaction of olefins with metal atoms (10). The reaction is catalyzed by cobalt hydrocarbonyl, iron pentacarbonyl, rhodium chloride, palladium chloride, the platinum-tin complex, and by several phosphine complexes a review of this field has recently been published (12). Two types of mechanism have been visualized for this reaction. The first involves the preformation of a metal-hydrogen bond into which the olefin (probably already coordinated) inserts itself with the formation of a (j-bonded alkyl radical. On abstraction of a hydrogen atom from a diflFerent carbon atom, an isomerized olefin results. 

Palladium chloride and metallic palladium are useful for carbonylating olefinic and acetylenic compounds. Further, palladium is active for decarbonylation of aldehydes and acyl halides. Homogeneous decarbonylation of aldehydes and acyl halides and carbonylation of alkyl halides were carried out smoothly using rhodium complexes. An acyl-rhodium complex, thought to be an intermediate in decarbonylation, was isolated by the oxidative addition of acyl halide to chlorotris(triphenylphosphine)rhodium. The mechanisms of these carbonylation and decarbonylation reactions are discussed. 

Phosphonate analogues of Reissert compounds (76) have been prepared and converted into 1-alkyl-isoquinolines (Scheme 49). Treatment of a number of A -methylisocarbostyrils with mercuric acetate gave rise to 4-mercuri-ated derivatives, which underwent insertion reactions with methyl acrylate and with styrenes in the presence of palladium chloride (Heck reaction). 

Generally, homocoupling of aryl and alkenyl halides has been the most widespread. Other halide derivatives, such as alkyl or alkynyl halides, have seldom been used. This is either because of problems during homocoupling (alkyl halides may easily undergo dehydro-halogenation) or because the homocoupled product (diynes) could be obtained by more convenient methods. Nonetheless, a rare example of homocoupling of alkyl halides catalyzed by palladium chloride in the presence of hydrazine as the reductant was published " however, this procedure is of limited synthetic value (Scheme 2). 

Although a rather new field of research, palladium-catalyzed 1,2-difunctionalization reactions have recently gained momentum. Major advances in this area have introduced suitable reactivity to incorporate chloride, bromide, oxygen and nitrogen-based nucleophiles into carbon frameworks. The common key step of all these transformations relies on the inter- or intra-molecular functionalization of intermediary alkyl-palladium bonds, for which several methods have been developed. The potential of all these approaches for organic synthesis is obvious, and the future looks bright for further developments in this field. 

The reactions discussed so far involved attack of soft nucleophiles on rr-alkene palla-dium(II) complexes. Hard carbon nucleophiles such as methyl lithium also react with these complexes.f The alkylation proceeds here by initial attack at the palladium atom. Subsequent di-insertion of the olefin into the Pd—C bond and di-/S-hydride elimination result in liberation of the alkylated alkene. The arylation of styrene by Grignard reagents can also be performed,the reaction being realized in the presence of stoichiometric or catalytic quantities of palladium chloride (Scheme 14). 

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