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Metal-alkyne complexes protecting group

Dendrimers with metal complex moieties in their branches require the prior incorporation of specific coordination sites into the dendrimer scaffold. Newkome et al. used such a dendrimer with twelve alkyne units for spot-on introduction of l,2-dicarba-c oso-dodecaborane groups (Fig. 4.59, above right) [127]. Moreover, on-target coordination with dicobalt-octacarbonyl to form a metallodendrimer with twelve dicobalt-hexacarbonyl units was also accomplished. These units can serve as protective groups on the one hand [128], and as catalysts on the other [129]. [Pg.137]

Ort/io-metallated palladium complexes of azo and hydrazobenzene catalyze the reduction by H2 of nitroaromatics, alkenes, alkynes, and aromatic carbonyl compounds. A palladium-aryl or bond in the precursor complex is a requirement for catalytic activity. The ligands are themselves susceptible to reduction. The kinetics of the reaction under 1 atm H2 have been measured. Palladium(O) complexes catalyze the hydrostannolysis of allyl and allyloxy carbonyl groups. The reaction can be applied to the selective protection-deprotection of aminoacid derivatives see equation (9). Alkenyl cyclopropanes carrying electron-withdrawing substituents are selectively hydrogenolyzed by Pd(0)/PBu3 catalysts... [Pg.372]

On protonation, the latter complex would produce the stereodefined conjugated diene as a single regioisomer. On the basis of this proposal, the authors checked the importance of the metallated alkoxide in a related experiment, showing that the reaction of an internal alkyne bearing a tert-butyldimethylsilyl (TBS)-protected hydroxy group with a preformed titanium alkyne complex led exclusively to a complex mixture of products [125]. [Pg.863]

At this stage, the hydroamination of both terminal and internal alkynes with primary and secondary amines can be achieved by judicious choice of substrate and catalyst. Notably, hydroamination with primary aUcylamines using late transition metals is rarely reported [187, 189-191], although the related reaction with anihne derivatives can be mediated by complexes of groups 9-12 metals. Once again, to reduce the nucleophilicity of the amine partner, protected amines are often used as alternative substrates. [Pg.1175]

In order for the 2-(trimethylsilyl)ethylthio unit to lose its protecting group upon treatment with the fluoride, the sulfur must be attached to an unsaturated carbon. Hence the fluoride mediated sulfur deprotection is feasible for 2-(trimethyl-silyl)ethylthio substituted (het)arenes, alkenes, alkynes, and acid derivatives such as carboxylic and selenothiophosphinic acid salts. In thiolate form, the substrates have value for the formation of self-assembled monolayers or as metal complexing agents. Simple addition of acid to the thiolate to give a stable thiol characterizes 2-(trimethylsilyl)ethanethiol as a simple M" (HS) equivalent that is only capable of a single substitution reaction. ... [Pg.619]

It is possible to temporarily protect reactive organic functional groups by complexing them to appropriate metal-centered fragments forming stable 18-electron complexes. This process makes selective reactions on other parts of the molecule possible, thus alkenes and alkynes are protected respectively by the 14-electron species Fe(C0)3 21-6,21.7 fragment Co2(C0)(S In the latter,... [Pg.489]

Homoleptic phenoxido complexes of the composition [Re(L)4] where L = 2,6-diisopropylphenoxide or 2,6-dimethylphenoxide have been prepared by the reaction of [ReCl4(THF)2] with the lithium salts of the ligands. The molecular geometry is square planar and the metal center is well protected from above and below the Re04 plane by the isopropyl groups and protects the complex from reactions with alkynes, whereas such a reaction and the formation of [Re(OC6H3-2,6-Me2)4(RC=CR)] adducts (R = Me, Eth, Ph) has been observed for the dimethyl derivative of the phenoxide. ... [Pg.334]


See other pages where Metal-alkyne complexes protecting group is mentioned: [Pg.135]    [Pg.47]    [Pg.42]    [Pg.73]    [Pg.169]    [Pg.281]    [Pg.152]    [Pg.76]    [Pg.362]    [Pg.316]    [Pg.303]    [Pg.388]    [Pg.435]    [Pg.77]    [Pg.1123]    [Pg.96]    [Pg.28]    [Pg.121]    [Pg.498]    [Pg.284]    [Pg.247]   
See also in sourсe #XX -- [ Pg.12 , Pg.13 , Pg.14 , Pg.15 ]




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Alkyne complexe

Alkyne complexes

Alkynes group

Alkynes metalated

Alkynes metallation

Complexes, alkyne-metal

Group 5 metal complex

Metal alkynes

Metal protection

Metalation alkynes

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