Alkynes alkynyl groups

The addition of alkynyl groups is discussed in Chapter 4, Alkynes. 

Once the protein is modified to contain an alkynyl group at its C-terminal it can be used to covalently link to its click chemistry reactant partner, an azide on the surface of an array. Other azido molecules also can be conjugated with an alkyne-protein to facilitate the detection or capture of the protein using affinity techniques. For instance, an azido-fluorescein reagent can be used to detect fluorescently the expressed protein in complex samples or an azido-biotin... 

React at room temperature for up to 3 days (or at 4°C, if the protein is not stable at ambient temperature). The optimal time of reaction is dependent on the protein being coupled and the number of alkyne reactive groups available. An alkynyl-protein added to the nanoparticles at a high molar ratio probably would reach maximal coupling yield in a matter of hours. 

The hydrocarbon substituents derived from alkynes are called alkynyl groups ... 

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving d.v-1 -borylbul-1 -en-3-yne derivatives. 1-Arylalk-l-ynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached.45... 

To our knowledge there is no experimental evidence for n bonding between a BeR2 unit and a simple alkene or alkyne ligand. However a n interaction has been found in the X-ray crystal structure of the dimeric dipropynylberyllium trimethylamine adduct (48). The unit cell of this molecule contains two independent centrosymmetric dimers in which the alkynyl groups exhibit different types of interaction with the beryllium atoms, one of them forming an effectively electron-precise dimer unit by n interaction as portrayed in XX. 

Woerpel and Clark identified silver phosphate as the optimal catalyst to promote di-ferf-butylsilylene transfer from cyclohexene silacyclopropane to a variety of substituted alkynes (Scheme 7.25).95 While this silver salt exhibited attenuated reactivity as compared to silver triflate or silver trifluoroacetate, it exhibited greater functional group tolerance. Both di- and monosubstituted silacyclopropenes were easily accessed. Terminal alkynes are traditionally difficult substrates for silylene transfer and typically insert a second molecule of the starting acetylene.61,90 93 Consequently, the discovery of silver-mediated silylene transfer represents a significant advance as it enables further manipulation of monosubstituted silacyclopropenes. For enyne substrates, silylene transfer the alkynyl group was solely observed. The chemoselectivity of the formation of 99f was attributed to ring strain as theoretical calculations suggest that silacyclopropenes are less strained than silacyclopropanes.96 97... 

Intramolecular /ra r-carbosilylation of terminal alkynes with alkenyl- and arylsilanes proceeds efficiently under catalysis by a Lewis acid (Equation (8)).41,41a Alkenyl- and arylsilanes bearing an alkynyl group at the (1- or ortho-position undergo -cyclization, while a-alkynyl-substituted alkenylsilanes are converted into tv/r/a-cyclization products. These cyclizations have been proposed to proceed also via a /3-silylcarbenium ion intermediate. However, the cationic center does not participate in bond formation. The intermolecular alkenylsilylation of terminal alkynes is rather limited in applicability.42... 

The ability of alkynyl groups to bridge two metals may be employed in the construction of heterometallic complexes in a controlled manner (Figure 4.20 Chapter 6). Many metals will react directly with terminal alkynes or acetylide salts under basic conditions however, use is often made of copper alkynyls as tr /i.v-alkynylating reagents [usually generated in situ with catalytic amounts of Cu(I) salts]. 

Alkoxy(l-alkynyl)carbene ligands are obtained either by addition of an alkynyl group to a carbonyl ligand or by transformation of a carbene ligand by generation of an alkyne unit. 

Several studies of the kinetics and effects of structure on reactivity lend support to a mechanism of oxidative coupling of the type first proposed by Bohlmann and coworkers The rate is second order with respect to Cu(ii) and alkyne, and varies inversely with [H+] . This is interpreted in terms of rapid steps involving displacement of a solvent molecule or other ligand from the coordination sphere of Cu(n) by an alkyne molecule, followed by acid dissociation of the coordinated alkyne to give an acetylide complex. In the rate-determining step, copper(ii) is reduced and simultaneously the alkynyl groups are coupled. These steps are summarized in equations (6), (7) and (8), where L represents a ligand—solvent, for... 

The RjZn compounds react with acidic hydrocarbons to split the original Zn— C bonds and form new ones. The rate depends on hydrocarbon acidity e.g., reactions with triphenylmethane proceed slowly and incompletely. Therefore, it is nearly impossible to obtain organozincs with stoichiometric compositions. More definite results are obtained with 1-alkynes, in which, depending on the molar ratio, one or two organic groups at Zn can be substituted for alkynyl groups ... 

Alkynes and functionally substituted alkynes may be synthesized either from starting materials that do not already contain the triple bond by elimination reactions, or the ethynyl and alkynyl groups may be introduced onto substrates by nucleophilic or electrophilic substitution reactions. 

Hitherto, only two papers appeared in the literature in which an alkynyl group was introduced into the 4 position of a monocyclic pyridazine using a Sonogashira reaction [52, 81]. Besides the previously mentioned 4-chloro-3,6-dimethylpyridazine (185), Bourguignon showed that electronically rich and sterically hindered A benzyl-4-bromo-and 4-bromo-6-phenyl-pyridazin-3-amine (82) are valuable coupling partners for different alkynes. 

A carbonyl compound can be successfully converted into an alcohol by treatment wifh BuaSnH in the presence of a Lewis acid. When a Lewis acid able to chelate strongly with alkyne 7t-bond was employed, e.g. GaCla, fhe formyl group located on the ortho position to fhe alkynyl group was regioselectively reduced with BuaSnH (Scheme 12.117) [220]. 

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