Trimethylsilylacetylene dimerization

Most of these catalytic systems are able to dimerize either aromatic alkynes, such as phenylacetylene derivatives, or aliphatic alkynes, such as trimethylsilylacetylene, tert-butylacetylene and benzylacetylene. The stereochemistry of the resulting enynes depends strongly on both the alkyne and the catalyst precursor. It is noteworthy that the vinylidene ruthenium complex RuCl(Cp )(PPh3)(=C=CHPh) catalyzes the dimerization of phenylacetylene and methylpropiolate with high stereoselectivity towards the ( )-enyne [65, 66], and that head-to-tail dimerization is scarcely favored with this catalyst. It was also shovm that the metathesis catalyst RuCl2(P-Cy3)2(=CHPh) reacted in refiuxing toluene with phenylacetylene to produce a... 

Dimerization of terminal acetylenes is a convenient route to an unsaturated C4 skeleton. The process was recently overviewed briefly [104]. Dimerization of trimethylsilylacetylene proceeds in the presence of [(PP3)RuH(H2)]BPh4,where PP3=P(CH2CH2PPh2)3 or [(PP3)RuH(N2)]BPh4 [105]. 

Another example of Pd(0)-catalyzed dimerizations of alkynes was reported by Ishikawa and co-workers. Terminal silylacetylenes 19, containing at least one phenyl group at the silyl moiety, in the presence of Pd(PPh3)4 underwent homodimerization in a head-to-head fashion to produce the corresponding bis-silylenynes 20 in reasonable yields (Scheme 7). The preferred anti-Markovnikov-type regiochemistry in these cases and also in the Pd(+2)-catalyzed homodimerization of trimethylsilylacetylene was explained with steric factors. ... 

Dinuclear platina-/3-diketones 193 and 194 are prepared from H2PtGl6, trimethylsilylacetylenes, and / -BuOH, and the dimeric structure with bridging chloro ligands has been confirmed by X-ray crystallography.Scheme 31 summarizes reactions of 193 toward organic reagents. 

The monoiodo derivative 74 was then converted to the ethynyl substituted phthalocyanine 76 by reaction with trimethylsilylacetylene ([Pd(PPh3)2Cl2], Cul, EtjN, THF, RT, 24 h) followed by desyUlation of 75 (TBAF, THF, 0 C-rt, 2 h, 65 %). Then 1,3-butadiyn bridged dimer 77 was obtained by copper catalysed Glaser homo-coupling reaction (CuCl, pyridine, rt, 3 days, 75 %) [62],... 

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