Palladium, organo- compounds

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

Recent work from Lipshutz [10] et al. even shows at least in CC-bond formations the replacement of the rather expensive palladium with nickel. Chloroarenes are coupled with organo zink compounds under nickel]0) catalysis. 

The preparation of organopalladium compounds by exchange reactions of palladium salts and organo-lead, -tin, or -mercury compounds is apparently not the only way that they can be obtained but it does seem to be the most useful way. Convincing evidence is now available to show that direct metalation of aromatic compounds with palladium salts (palladation) can occur. Since the initial report of Cope and Siekman 32> that palladium chloride reacted readily with azobenzene to form an isolable chelated, sigma-bonded arylpalladium compound, several additional chelated arylpalladium compounds have been prepared. 

Acylation of organozinc reagents. Reaction of acyl chlorides with organozinc compounds catalyzed by palladium-phosphine complexes provides a general synthesis of ketones. The organozincs are readily available by treatment of the corresponding organo-lithium with ZnCh. Alkenylzinc compounds and a,p-unsaturated acyl chlorides react with retention of the stereochemistry. Isolated yields of ketones are 55-90%. 

CONJUGATE ADDITION (3-Bromopropion-aldehyde ethylene acetal. 1-r-Butylthio-1 -trimethylsilyloxyethylene. Cryptates. l-EthylsuIfinyl-3-pentanone. HexamethyF phosphoric triamide. Ketene bis-(methylthio)ketal monoxide. Organo-lithiuni compounds. Palladium(II) chloride. Phase-transfer catalysts. 

Applications of nuclear magnetic 179 resonance to the study of organo- (380) metallic compounds Reactions involving organometallic 20 compounds of rhodium, iridium, (77) palladium and platinum a survey of NMR studies... 

A more general solution to the problem is to change the nucleophile from an organo-lithium or copper species to an organo-palladium compound and this leads on to the Heck reaction. 

When an organotin compound is the nucleophile, the coupling is called Stille coupling after J. K. Stille of Colorado State University, the inventor.26 In chapter 15 we saw how organo-tin compounds are sources of radicals, but with palladium catalysis the reaction changes. We shall start with an example which may look trivial but is very important for this chapter. Reaction of readily prepared 1,1-dibromoalkenes 184 with tributyltin hydride under Pd(0) catalysis gives Z-l-bromoalkenes 185 with high stereoselectivity.27... 

M.R. Netherton - G. C Fu Palladium-Catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organo-metallic Compounds... 

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