Hydrocarbons acetylenic

Two groups of workers have reported a new synthesis of the acetylenic linkage from carboxylic acid esters. The key step is the reductive elimination of the enol phosphate of a /3-keto-sulphone with sodium amalgam or sodium in liquid ammonia. The novelty of this procedure is that it is eminently suitable to the synthesis of some important classes of acetylenes, such as dialkylacetylenes and 

Prolonged reaction of the Wittig reagent chloromethylenetriphenyl-phosphorane (102) with aromatic aldehydes, in the presence of excess potassium t-butoxide, allows a one pot procedure to the corresponding arylacetylenes 

Verboom, H. Westmijze, H. J. T. Bose, and P. Vermeer, Tetrahedron Letters, 1978,1441. 

Terminal acetylenes can be alkylated to give chain-lengthened internal acetylenes in good yield, either by the rapid addition of trialkylalanes in the presence of nickel(ii) catalysts or by electrochemical addition of organoboranes. Hydroalumination may be used in a convenient conversion of terminal olefins into the corresponding acetylenes. An improved procedure for the synthesis of cyclo-octyne from cyclo-octene by a bromination-dehydrobromination sequence has been reported.  

Conditions have been described where both vinyl sulphides and vinyl sulphox-ides may serve as acetylene equivalents. Thus the super-base potassium 3-aminopropylamine (KAPA), reacts readily with the internal vinyl sulphide (110) at room temperature, to produce the corresponding terminal acetylene (111).  

The copper(i) chloride decomposition of the anions (123) or (124) produces the stable cyclic tetra-acetylene (125) in 5% yield. Y-Ray data showed the acetylenic carbon atoms have bond angles of about 166° and the two bowed diyne units lie in different planes. The air-sensitive yellow pentaene (126) can actually be isolated 

Flash pyrolysis of 4-arylmethylidene-3-methyl-5(4//)-isoxazolones (127) yields phenylacetylenes with alkoxy, chloro, dimethylamino and hydroxy substituents. The reaction proceeds via an arylmethylidene carbene as has been described for a 

A ready route to phenylpropynenitrile involves refluxing copper phenylacetylide and cyanogen bromide in ether-acetonitrile. The yield was 60 % but some diphenyl-butadiyne is formed as a by-product. Nitroacetylenes are reactive compounds, and two routes to these compounds have been described starting from trialkyltin acetylides via electrophilic cleavage of the Sn bond-C bond. -  

A catalytic amount of dihydridocarbonyltris(triphenylphosphine)ruthenium causes the dimerization of t-butylacetylene at 100 °C in benzene to a mixture containing 88% of /ra/ij-l,4,-di-t-butylbutatriene. Colbatocene is an effective 

3 -Substituted di-2-propynl ethers react with acetylenes in the presence of tris(triphenylphosphine)rhodium(i) chloride or dicarbonylbis(triphenylphosphine) nickel(o) to give 1,3-dihydroisobenzofurans. The intermediate rhodium complex (130) could be isolated and used in heterocyclic synthesis. The oligomeric Pd (DMAD 2 (DMAD=dimethylacetylene dicarboxylate) complex is an efficient 

A general synthesis of terminal acetylenes (278) has been developed by Ikegami et al, whereby the vinylstannane derivatives (277), prepared from the aldehydes (276), are treated with lead tetra-acetate. The method will tolerate a wide range of sensitive functionality, such as double bonds, epoxides, and silyl and THP ethers. 

Tertiary alkyl-acetylenes are not usually available by the reaction of metal acetylides with tertiary alkyl h ides, but the Lewis-acid-catalysed alkylation of trimethylsilylacetylenes (279) can be applied to the synthesis of tertiary-alkyl-substituted acetylenes (280).  

Nakazaki, K. Yamamoto, M. Maeda, O. Sato, andT. Tsutsui,/. Org. Chem., 1982,47, 1435. 

The first examples of the synthesis of functionalized acetylenes (283) by metathesis, using the molybdenum catalyst (282) on the 1-phenylbutynes (281), have been reported, the yields being dependent on the substitution pattern.  

Tomoda and his group have reported two procedures for the preparation of l-(phenylseleno)acetylenes from terminal acetylenes which tolerate diverse functionality. Miura and Kobayashi have shown that terminal acetylenes (284) can be transformed into the acetylenic sulphones (287) by the addition of phenyl aryl selenosulphonates (285) and subsequent oxidative elimination of phenyl-selenenic acid from the vinyl sulphones (286).  

Normant and his co-workers have described a new simple two-step procedure for the conversion of alkyl halides into the corresponding chain-elongated acetylene in good yield. The procedure involves reaction of the halide with dichloromethyl-lithium in the presence of one equivalent of HMPA. If the group R is branched, the alkyl iodide is preferred over the bromide. Treatment of the 

Flash vacuum pyrolysis of 4-methylene-5-oxo-4,5-dihydro-l,2-oxazoles (93) at 700—800 C gives terminal acetylenes in good yield, provided that (93) is volatile and stable at this temperature. Thus a range of heteroaromatic aldehydes can be converted into the corresponding homologous acetylenes by this route. 

8 Conjugated Enynes and Miscellaneous Mixed Unsaturated Moieties 

Other methods reported to give conjugated enynes (144) include the ready addition of Grignard reagents to cumulenic ethers (143) in the presence of small amounts (10 mole %) of copper(l) bromide,the tra 5-addition of organo-aluminium hydrides to disubstituted diynes to give tran -enynes (145), and the 

Schrock and his co-workers have prepared several tungsten(vi) neopentylidyne complexes, e.g. (174), which react with diphenylacetylene to give the product of acetylene metathesis (175). More importantly, the complexes catalytically metathesize many acetylenes with remarkable ease.  

Olefins of the type (177), which are readily prepared from the keten-anthracene adduct (176), undergo retro-Diels-Alder reactions to give high yields of mono- or di-substituted acetylenes.  

Tarnchompoo, Y. Thebtaranonth, S. Utamapanya, and P. Kasemsri, Chem. Lett., 1981, 1241. 

Symmetrical or unsymmetrical diarylcyclopropenones (178) undergo smooth decarbonylation on treatment with alumina pellets in refluxing o-dichlorobenzene, providing a versatile route to diarylacetylenes (179). Symmetrical diarylacetylenes (181) can be prepared in moderate yields by treating substituted nitrostyrenes (180) with hydrogen peroxide and triethylamine. Nitroepoxides are probably the initial products of these reactions.  

The Z-jS-silylvinyl sulphoxide (187) undergoes rapid jy -elimination on heating with the formation of an acetylenic bond. By contrast, the geometry of the corresponding E-isomer (188) does not allow elimination to take place. 

Dehydrohalogenations can be performed under mild conditions using solid potassium t-butoxide in petroleum ether in the presence of catalytic amounts of 18-crown-6. These conditions are particularly effective for converting 1,2-dihalides (from terminal alkenes) and 1,1-dihalides (from aldehydes) into terminal acetylenes, and gem-dihalides from symmetrical ketones into internal acetylenes. 

Sodium 3-aminopropylamide, a base used to effect the acetylenic zipper reaction, is conveniently prepared from sodium hydride in 1,3-diaminopropane at 70 C without problems associated with foaming, often encountered in previous procedures.  

Reagents i, =—SiMej-Et3N-2 mol% (PPh3)2PdCl2-l moI% Cul ii, NaOH-MeOH-HjO 

The lithium acetylide salt of methyl or ethyl propynoate, prepared by treatment of the ester with n-butyl-lithium at low temperature, adds rapidly to a variety of aldehydes and ketones to give 4-hydroxyalk-2-ynoates.  

Improved procedures have been reported for the conversion of aliphatic or aromatic aldehydes into 1-bromoacetylenes with one extra carbon atom (carbon tetrabromide, triphenylphosphine, and benzyltrimethylammonium bromide), and for the preparation of 1-chloroacetylenes from the corresponding terminal acetylenes (n-butyl-lithium and iV-chlorosuccinimide).  

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CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Ethylenic and acetylenic hydrocarbons combust spontaneously when they come into contact with nitric acid, within a millisecond. 

There are no liquid alkynes which can be conveniently prepared by the elementary student. Some of the properties of acetylenic hydrocarbons may be studied with the gas, acetylene. Although the latter may be prepared in moderate yield by the addition of ethylene dibromide to a boiling alcoholic solution of potassium hydroxide or of sodium ethoxide,... 

Fraction 2 and 3 (P.E.) provided, besides the sesquiterpene hydrocarbon mixture, a compound which on the basis of H NMR and MS spectral evidence was shown to be the acetylenic hydrocarbon pentayneene (9) C,Ht> previously isolated from A. artemisiifolia... 

Although lithium aluminium hydride does not reduce alkenes or acetylene hydrocarbons, it reduces allylic alcohols and their acetylenic counterparts. Thus cinnamic acid is reduced to dihydrocinnamyl alcohol. 

Very often the carbon framework of the future allene is already present in the substrate and often it is propargylic in nature. For example, base-catalyzed isomeriza-tions of acetylenic hydrocarbons - with the triple bond in a non-terminal (40) or terminal position - were often used to prepare allenic hydrocarbons in the early days of allene chemistry [8]. The disadvantage of this approach consists in the thermodynamic instability of the allenes produced if not prohibited for structural reasons, the isomerizations do not stop at the allene but proceed to the more stable conjugated diene stage. In practice, complex mixtures are often formed [9] (see also Chapter 1). 

Various intermolecular coupling reactions involving acetylene hydrocarbons have been reported to lead to vinylallenes. For example, 1-phenylpropyne (93), after activation with Hg(II) chloride, is first metalated by butyllithium treatment, then trans-metalated with zinc bromide and finally coupled with 1-iodo-l-phenylethene (94) in the presence of tetrakis(triphenylphosphine)palladium to provide the diphenylvinyl-allene 95 in moderate yield (Scheme 5.12) [31]. 

Explosive Properties and Decomposition of Copper Derivatives of Acetylene Hydrocarbons... 

Acetylenic Compounds are organic compounds contg at least one triple bond -O C-. They may be hydrocarbons, alcohols, acids, aldehydes, etc. The acetylenic hydrocarbons include, in addition to acetylene (qv), the higher members, such as allylene or propyne H,CC s CH, crotonylene or butyne -2 HjCC i C.CHj, valerylene or pentyne - 2 H, C2.C C.CH, etc... 

Expl properties and decomposition derivs of acetylene hydrocarbons 6 E439... 

Some of the many solvents that have been examined for certain hydrocarbon separations are listed in Table 13.8 part (c) for n-butane and butene-2 separations includes data showing that addition of some water to the solvent enhances the selectivity. The diolefins butadiene and isoprene are available commercially as byproducts of cracking operations and are mixed with other close-boiling saturated, olefinic and acetylenic hydrocarbons, often as many as 10-20 different ones. The most widely used extractive... 

KUCHEROV REACTION. The hydration of acetylenic hydrocarbons with dilute sulfuric acid in the presence of mercuric sulfate or boron trifluoride as catalyst. 

Reaction XXXIV. (c) Action of Carbon Dioxide on Sodium Acetylides in Dry Ether. (B., 12, 853 J. pr., [2], 27, 417 B., 33, 3586.)—This is an example of the great activating influence of a triple bond. When carbon dioxide is passed into a solution of the sodium derivative of an acetylenic hydrocarbon in dry ether, direct addition takes place to give the sodium salt of the next highest acetylenic carboxylic acid. For example, sodium allylene yields sodium tetrolate—... 

As described in Sec. 2.2.4.1, the acetylene hydrocarbons frequently have a bridge function [76,77a]. An example of their use is the synthesis of 7t-complexes of propargyl alcohol with copper(I) chloride (3.65) [77a] ... 

M2+02 (M = Mg, Ca, Sr) coordinatively unsaturated pairs are able to abstract a hydrogen ion from acetylenic hydrocarbons following the reaction path shown in Scheme 4 (—, surface plane R, alkyl group), with formation... 

The nitration of acetylene hydrocarbons proceeds in a more complex way than that of olefins. The first member of the series-acetylene-undergoes various reactions, for example, with nitric acid (see p. 82 and p. 599) Tolane (diphenylacety-lene) is nitrated with N204 to form dinitrostilbene. Two products are formed which are presumably a- and p- stereoisomers ... 

The acetylene hydrocarbons, CnH2n 2j polymerize without loss of hydrogen. 

All hydrocarbons take up nitrogen, forming probably cyclical polyamines methane and ethylene hydrocarbons seem to give tetramines and acetylene hydrocarbons, diamines. 

DegussaAG/LindeAG Acetylene Hydrocarbons (C, - Cs) Electric arc pyrolysis, hydrogen coproduction 1 1988... 

If this pretreatment applies to both the fresh C cut and the recycle of the effluent rich in acetylenic hydrocarbons produced by the subsequent separation stage, the buta-... 

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