Acetylene derivs alkynes

Common Names The common names of alkynes describe them as derivatives of acetylene. Most alkynes can be named as a molecule of acetylene with one or two alkyl substituents. This nomenclature is like the common nomenclature for ethers, where we name the two alkyl groups bonded to oxygen. 

An elegant method for linking terminal alkynes with aromatic compounds and olefins is the Sonogashira reaction [15]. The palladium-catalyzed reaction enables the simultaneous introduction of two or even more alkyne units and thereby makes it possible to synthesize acetylene derivatives, for example hexaalkynyl-benzenes [16], (eq. (7)), which can be obtained only with difficulty by other methods. It has been shown by Herrmann, Beller, and co-workers that the copper reagent is not necessary as a co-catalyst for the coupling of terminal alkynes with sp -carbon halides. By using phosphapalladacyclic catalysts 1 the... 

As an improved alternative to the direct cyclocarbonylation of allylic halides and acetylene derivatives, a two-step procedure has been reported49. Thus, the addition of allylic halides to acetylenic derivatives is catalyzed by palladium(II) complexes, such as bis(acetonitrile)bromo-palladium(ll), followed by cyclocarbonylalion of the resulting cfs-adducts of the alkyne with tetracarbonylnickel in acetonitrile containing precise amounts of methanol and triethylamine. This is a better procedure for the preparation of cyclopentenones than direct cyclocarbonyla-tion mediated by tetracarbonylnickel, especially for monosubstituted or weakly polarized, disubstituted acetylenes. 

The reactions of the cationic complex 4 with acetylene or alkynes having electron-withdrawing substituents afford the terminal vinylidene complexes [Cp RuCl(/i-SPr%Ru(=C=CHR)Cp ](OTf) 8 (R = H, COOMe, or COMe) as shown in Scheme 2. When aromatic terminal alkynes are used, two molecules of the alkyne are incorporated into the diruthenium centre of 4 to give the cationic diruthenacycle complexes 9, which are probably formed via the alkynyl-vi-nylidene and butenynyl intermediates 10 and 11 derived from 8. In fact, the butenynyl complex 11 (R = R = Fc) has been isolated from the reaction of 4 and ferrocenylacetylene. Coupling of two different alkynes takes place in a similar manner to give the diruthenacycle complexes 12 when the vinylidene complexes 8b and 8c are treated with p-tolylacetylene. ... 

The alkyne-Co2(CO)6 complexes 1 are the binuclear cluster complexes of the acetylenic derivatives with the hexacarbonyldicobalt moiety. These complexes can be readily prepared by treatment of alkynes with commercially available octacarbonyldicobalt [Co2(CO)g] and can regenerate the parent triple bond functionality under some mild oxidation conditions. Two synthetically very useful reactions have so far been developed by taking advantage of the characteristic properties of the alkyne-Co2(CO)6 complexes 1 one is so-called Nicholas reaction" and the other is so-called Pauson-Khand reaction (Scheme 1). The alkyne-Co2(CO)6 complexes 1 possessing a hydroxyl group or its equivalent at carbon p- to alkyne moiety (propargyl alcohol derivatives) could easily... 

Although the yields tend to be modest, coupling of alkynyl, alkenyl, and allylic halides to terminal alkynes in the presence of a cuprous halide and an amine (e.g. Et N, pyridine) by the Cadiot-Chodkiewicz reaction provides a direct route to acetylenic derivatives that are of interest in the construction of vitamin A (1) and carotenoids. For example, heating the acetylenes 104, 95 or 105 with the bromides 106 and 107 in the presence of cuprous chloride and an amine in methanol provides a convenient route to the corresponding acetylenic retinoids 108, 109 and 110 [53,54]. Similarly, heating 3-bromobut-2-en-2-ol with the acetylene 105 gives 11,12-didehydrovitamin A (108) [53] (Scheme 26). 

A novel insoluble green complex of palladium(II) and N,N -salicylideneethylenedi-amine (salen) functions as a selective heterogeneous catalyst, notably for the reduction of alkynes in the presence of alkenes, and of the latter in the presence of certain functional groups. E ciVEthylene from acetylene derivs. A soln. of startg. acetylene deriv. in EtOH hydrogenated for 17 min in the presence of the palladium(ll) complex (prepared from potassium tetrachloropalladate, salen, and triethylamine) cis-product. Y 100%. Reduction of alkenes is considerably slower however, terminal olefins may be reduced in the presence of internal olefins esters, oxo compds., dibenzyl ether, and iodobenzene were unaffected. F.e., also ar. amines from nitro compds. s. J.M. Kerr et al.. Tetrahedron Letters 29, 5545-48 (1988). 

In contrast, cyanoynamines react with phenyl isocyanate via an initial [2+2] cycloaddition reaction across the CM3 bond of the isocyanate to give a quinoline derivative Intramolecular cobalt catalyzed cyclization of alkynes and isocyanates was employed in the total synthesis of camptothein, an antitumor alkaloid. The key step of the synthesis involves the reaction of the acetylene group-containing isocyanate 185 with the acetylene derivative 186 to give 187. ... 

A new synthesis of aldehydes with 2-methyl-2-thiazoline has the advantage of releasing the aldehydes from the thiazolidine intermediate under neutral conditions . Acetylene derivatives can be obtained from aldehydes via dibromomethylene compounds Novel reactions of alkynes with cationoid electrophiles have been published. -Diketones and 2-ketoalkoximes can be obtained by this reaction from acid chlorides and aliphatic nitro compounds respectively Addition of aldehydes to activated carbon-carbon double bonds occurs smoothly in the presence of cyanide ions as catalysts . Poly- -carbonyl compounds have been prepared by condensation of two anions, whereby the enolate salt of a y8-keto ester condenses as an electrophilic anion with strong nucleophiles such as the dianion of benzoylacetone. ... 

Copper-bis oxazolidinone complex catalyzed the addition of alkyl and aromatic alkynes to the imine formed by the reaction of ethyl glyoxylate and p-anisidine, providing an easy access to chiral p,Y-alkynyl a-amino acids in good yields (61-80%) and enantioselectivities (66-74%) [38]. The presence of the two phenyl groups in the ligand was found to be crucial in the enantioselectivity enhancement and reduction of the reaction time, with aryl alkynes providing better results than alkyl acetylene derivatives [39]. Another type of Cu(II)-pybox complex led to excellent results in terms of enantioselectivities (28-93% yield, 81-98% ee) in the reaction of aliphatic alkynes with aldehydes and amines [40]. 

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