Alkynyl group

Alkynyl groups are formed from allies by removing one H atom. The most common allqmyl groups are ethynyl, 1-propynyl, and 1-butynyl 

The ICJPAC name of the simplest alkyne C2H2 is ethyne, however it is more often called as acetylene. 

The reactivity of alkynyl substituents was not directly addressed in CHEC-I. Methoxylation of 

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Xenon Bonded to Carbon. A number of stmcturally well-characterized compounds containing Xe—C bonds are known. In all cases these occur as colorless salts of xenonium cations, R—Xe" where R is a fluorophenyl or alkynyl group. The formation of the pentafluorophenylxenon(II) cation, CgFgXe+ [121850-39-3] (-30W) and CHgC N (0°C) solutions with the anions B(C3F3)3F [121850-40-6], B(CgFg) 2F- [123168-25-2], and... 

Although the activity of methoxylated monobactams could be improved by appropriate side-chain modifications, difficulty of synthesis and poor chemical stabihty focused attention on the nonmethoxylated analogues. Both high intrinsic activity and excellent P-lactamase stabiUty are exhibited by monobactams that combine C-3 arninothia2ole oxime side chains and 4-alkyl, 4-alkenyl, and 4-alkynyl groups (19). 

Compounds containing aiyl and alkynyl groups have also been prepared (199) ... 

When both double and triple bonds occur in the same molecule, the lUPAC system recommends the use of both endings -ene, and -y ne, with the former always preceding the latter in the name. Common alkynyl groups are... 

As with alkyl and alkenyl substituents derived from alkanes and alkenes, respectively, alkynyl groups are also possible. 

Note Such halogenation can be done by addition of elemental halogen to alkenyl or alkynyl groups or by replacement of one or more of the hydrogen atoms attached to alkyl or aryl substituents, using a variety of reagents. 

Scheme 10.1 gives some representative examples of laboratory syntheses involving polyene cyclization. The cyclization in Entry 1 is done in anhydrous formic acid and involves the formation of a symmetric tertiary allylic carbocation. The cyclization forms a six-membered ring by attack at the terminal carbon of the vinyl group. The bicyclic cation is captured as the formate ester. Entry 2 also involves initiation by a symmetric allylic cation. In this case, the triene unit cyclizes to a tricyclic ring system. Entry 3 results in the formation of the steroidal skeleton with termination by capture of the alkynyl group and formation of a ketone. The cyclization in Entry 4 is initiated by epoxide opening. 

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

Various homo- or heteronuclear cluster species which contain both a- and 7r-bonded alkynyl groups have been synthesized and characterized, e.g., [Ag5(C=CPh)6]-,278... 

The formation of the indole moiety has found immense attention, since it exists in many bioactive compounds such as the indole alkaloids [302]. Whilst the Fischer indole synthesis remains the most important procedure, during the past few years several transition metal-catalyzed syntheses have been developed. Recently, a Cu11-catalyzed cyclization of anilines containing an ortho-alkynyl group was published by Hiroya and coworkers [303], which allows a double cyclization in domino fashion to provide annulated indoles. Thus, reaction of 6/4-92 in the presence of... 

The first polynuclear structures with gold(i) centers coordinated to isocyanide and alkynyl groups were prepared through a novel exchange of alkynyl ligands. This special route became necessary, because the coupling of certain complexes proved elusive (Equation (40)) AuCl complexes of isocyanides with terminal alkynyl groups are subject to decomposition upon treatment with a variety of auxiliary bases. 

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... 

An alternative method of modifying proteins to contain alkynyl groups is to use the propargyl-PEGj-NHS ester compound described in Chapter 18, Section 2. This reagent will react spontaneously with available amine groups in proteins to form an amide bond without the need to use EDC, as in the following protocol. 

The action of iV-methylhydroxylamine on enantiopure 4-formylazetidin-2-ones bearing an N-tethered alkynyl group 89 has been studied and products formed by 1,3-dipolar cycloaddition and reverse Cope elimination isolated, e.g. 90 <00TL1647>. 

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