Acetylene derivatives, terminal halides

Sodium hydride dimethyl sulfoxide Terminal acetylene derivatives from halides... 

Lithium acetylide-ethylenediamine Terminal acetylene derivs. from halides Hal C = CH... 

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... 

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). 

Vinylidenes have been transferred from a variety of precursors to olefins to produce methylenecyclopropanes . Because of ready intramolecular hydrogen shifts to give terminal acetylenes, the addition of vinylidene to olefins is rather limited to 2,2-disubstituted species. The methodologies so far developed include (1) gem-dibromides, 7, with MeLi, (2) vinyl halides " or vinyl triflates, 8 " with r-BuOK, (3) the fluoride ion promoted decomposition of vinylsilanes, 92 2,243 4 thermolysis of mercuric derivatives, 10, at 250 (5) decomposition of vinylazo compounds, 11, at 25 (6) the alkaline... 

Methylene chloride has high solvent power for magnesium halide etherates, even those derived from terminal acetylenes, which are sparingly soluble in ether, and is recommended for use in Grignard reactions (comparable to the more expensive tetrahydrofurane).- Thus a reagent is prepared in ether as usual but the solvent is replaced by methylene chloride prior to subsequent Grignard reaction. 

Me3Si)2NP=ESiMe3 (1 E = CH 2 E = N) with a diverse series of unsaturated organic substrates are reported. For example, phosphines 1 and 2 react readily with allenes via an ene process to afford novel phosphorus-substituted dienes or with 2-butyne to give allenic phosphines. Other derivative chemistry, including the addition of terminal acetylenes and acetylenic alcohols to the P=E bond as well as some related reactions with acetylenic halides and both P- and y-diketones, is also described. 

Unsymmetric alkynylaluminum derivatives can be prepared by a) the reaction of sodium acetylides with dialkyl- or diaryluminum halides [92-94] (6) the reaction of terminal acetylenes with aluminum hydrides in donor solvents [95,96] and (c) the reaction of terminal acetylenes with triorganoaluminums, especially with trimethyl- or triphenylaluminum [91,97]. Where applicable, the last method gives an unsolvated product under mild, simple conditions. 

The iV-propargylaminophosphines (78) readily rearrange to give the azabuta-dienylphosphine (79) via intramolecular nucleophilic attack of phosphorus at the terminal acetylenic carbon. Full details have now appeared of the reactions of 2 -1,2,3-diazaphosphole derivatives (80) with alkyl halides, giving 2,3-disub-stituted indoles as the major product. Several examples of the attack of phosphines at carbon of a, -unsaturated carbonyl compounds have been described. The betaine (81) is the active intermediate in the triphenylphosphine-induced polymerization of maleic anhydride. Phosphines also catalyse the... 

Reactions with butyllithium/tetramethylenediamine Silylacetylenes from halides Protection of terminal acetylene groups as trimethylsilyl derivatives... 

The substrate can be prepared by standard etherification reaction of a phenol derivative with a propargylic halide [lb]. Further carbon-carbon bond forming reactions of the terminal acetylenic carbon via metal acetylide provides a variety of substituted propargyl aryl ethers. Direct preparation using substituted propargyl ether is also possible. 

Terminal acetylenes can be carbonylated (1 atm. CO-CuC -PdCL catalyst-ROH) to give a,/S-acetylenic esters in 60—70% yields this reaction would seem to be a very expedient alternative to the conventional carboxylation procedure using acetylenic anions.The acetylenic ester anion (182) can be derived from methyl propiolate using Bu"Li at -120 and condenses cleanly with carbonyls. Ethyl alk-2-ynoates (183) can be converted into the alk-3-ynoates (184) by electrolysis in HMPA or DMF containing excess alkyl halide (R X) yields are 60—80% when R = alkyl but the reaction fails when R =... 

Alkynide ions react with carbonyl groups in much the same way as Grignard reagents do. We recall that these ions are effective nucleophiles that will displace a hahde ion ftom an alkyl halide to give an alkylated alkyne. The alkynides are prepared in an acid-base reaction with acetylene or a terminal alkyne using sodium amide in ammonia. If a carbonyl compound is then added to the reagent, an alcohol forms after acid work-up. If the alkynide is derived ftom acetylene, an acetylenic alcohol forms. 

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