4- aryl-1 -alkyne alkene

Relevant complexes have been isolated and fully characterized (4-10, 13-lb). The resulting arylpalladium complex 8 is able to react with various compounds such as terminal alkenes, alkynes, aryl boronic acids or hydrogen-transfer agents to give an organic molecule and palladium(O) (3, 17, 18). 

Polymetal compounds, arsenic, antimony, bismuth, 3, 909 Polymetallacarboranes, alkene, alkyne, and aryl linkages,... 

Aryl-A3-iodanes bearing an electron-deficient alkyl ligand such as aryl(sul-fonylmethyl)-A3-iodanes (Section 3.2.7) and aryl(perfluoroalkyl)-A3-iodanes are relatively stable. A series of (perfluoroalkyl)phenyl-A3-iodanes 96 were synthesized in good yields by treating bis(trifluoroacetoxy)-A3-iodanes with benzene in the presence of triflic acid [47]. The AModanes 96 transfer the perfluoroalkyl groups to a variety of nucleophiles with reductive elimination of iodobenzene. The nucleophiles involve Grignard reagents, alkyllithiums, enolate anions, alkenes, alkynes, trimethylsilyl enol ethers, arenes, phenols, and thiols. In these reactions, the AModane 96 serves as a source of the perfluoroalkyl cation and, in... 

Arylation is possible by the addition of triplet aryl cations to neutral nucleophiles such as alkenes, alkynes, enols, and enamines (photo SN1 mechanism). For alkenes, the... 

Shim and coworkers have published several examples of the 2+2 between aryl-substituted alkynes and alkenes. Their data suggests that the singlet and triplet pathways give rise to the observed cyclobutenes. Exciplex emission was detected for the alkyne-alkene pairs. 

Dinitro-6-phenyliodonium phenolate (146) is a stable iodonium zwitterion484. It reacts under photolytic conditions with various alkenes, alkynes and aromatic compounds to afford 2,3-dihydrobenzo[ ]furans, benzo[6]furans and 6-aryl-2,4-dinitrophenols. The mechanism involves hypervalent iodine compounds (iodinanes, 147) and is illustrated for the reaction with an aromatic compound (equation 127). Compounds 148 are the major products when ArH = PhH, PhOCH3 or 1,4-dimethoxybenzene. With furan and thiophene, 149 is the principal product. The reaction does not proceed with chlorobenzene and nitrobenzene. 

Not only have NHC - Pd(0) catalysts been shown to be stable under hydrogenation conditions, but they were able to hydrogenate 1-phenyl- 1-propyne with remarkable efficiency and selectivity [192], The best results were obtained with [Pd N,N -bis(2,6-diethylphenyl)imidazol-2-ylidene ] as catalyst. This complex can be efficiently formed in situ starting from [Pd(ma)(nbd)] and selectively semihydrogenated aryl-substituted alkynes to Z alkenes (Scheme 26). 

Sml2-mediated radical cyclisations involving alkyl, alkenyl and aryl radical intermediates can be used to construct efficiently five-membered and, in certain cases, six-membered ring systems. This approach provides a useful alternative to trialkyltin hydride-mediated methods as toxic reagents and problematic tin byproducts are avoided. In addition, the use of Sml2 to induce radical cyclisations has led to the development of a number of powerful, radical/anionic sequential processes for the construction of complex systems. Sequential reactions involving radical-alkene/alkyne cyclisations are discussed in Chapter 6. 

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