Palladium catalysis allylation, alkynes

Hi. Carbon-silicon bonds. Following the earlier reports mentioning the palladium-catalysed addition of organosilylstannanes to alkynes or isonitriles , Mori and coworkers realized tandem transmetallation-cyclization reactions with bifunctional halogeno triflates and Bu3SnSiMe3 18. The reactivity of 18 under palladium catalysis was used for the silylstannylation of alkenes or the synthesis of allylic silanes via a three-component (aryl iodide - - diene - - 18) coupling reaction. Recently, a similar... 

Using catalysis by palladium systems, allylic halides show little tendency to add. However, with nickel(O) catalysts [e.g., Ni(cod)2] allylic halides add to norbornene. in contrast to vinyl and aryl halides9. The palladium system also catalyzes the coaddition of alkynes and benzylic halides to strained bicyclic alkenes10- u. Thus, addition of methyl 2-[3-(chloromethyl)phenoxy]acetate and optically pure (S)-l-octyn-3-ol to norbornene, norbornadiene or 7-oxanorbornene 4 leads to diastereomeric adducts 5, used as precursors of interphenylene prostaglandin endoperoxides, in 34-58% yield. No diastereomeric ratios were reported. 

The alkene, allyl, and alkyne complexes of Pd and Pt have been discussed to a large extent in earlier Sections, as have the use of palladium species in catalysis (Chapters 23 and 24). Here we deal mainly with complexes of the type MXHL2 and MXRL2 where X is halogen, R is an alkyl or aryl group and L is usually a tertiary phosphine. 

Other examples of microwave-assisted catalysis include allylic alkylation, both palladium catalyzed and molybdenum catalyzed. In the latter case, air stable precursor complexes could be used under non-inert conditions. Microwave-enhanced Pauson-Khand reactions have also been reported, as have hydroamination of alkynes, and metathesis of functionalized alkynes. " Recently, microwave enhancement has been applied to C-H activation reactions, for example, for the formation of functionalized heterocycles, allowing the reaction to be performed with no solvent purification and minimal precautions to exclude air. A solvent-free chelation-assisted hydroacylation... 

Joint catalysis by tin(IV) chloride and zinc chloride induces coupling of the acetal 114 with the alkyne 115 to give the propargyl ether 116. Allyl halides condense with terminal alkynes in DMF in the presence of copper(I) iodide, potassium carbonate and tetrabutylammonium chloride under phase-transfer conditions to afford eneynes, e.g. equation 19. Palladium-catalysed coupling reactions of 1-bromoallenes with terminal acetylenes have been reported for the first time thus acetylene and the allenes 117 (R R = Me or Et) in triethylamine in the presence of tetrakis(triphenylphosphine)palladium and... 

Many examples of alkene and alkyne insertion into metal-carbon bonds can also be found in the section on homogeneous catalysis. Other recent examples include the insertion of conjugated dienes into palladium-allyl bonds, olefin arylation in the presence of palladium acetate, and the reaction of ethylene with arylmagnesium halides in the presence of nickel chloride. Reaction of isocyanates with nickel-ethynyl compounds... 

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