Acetylene reaction with organic halides

Alkylcopper reagents (CuR-MgXj,CuR-LiX) add to acetylene or alkynes in a cis manner under mild conditions. This method generates alkenyl or alkylcopper intermediates, which subsequently are quenched in a second reaction with organic halides or other substrates ... 

A conjugated terminal acetylene is an important intermediate in organic synthesis. The reaction of acetylene gas with organic halides preferentially gives only internal acetylenes because of the higher reactivity of monosubstituted acetylenes than that of acetylene gas. 

Coupling reactions with organic halides [62,71], cyclization addition of acetylenes with carbon dioxide, hydrogenations, reductions, oxidations, alkoxylations, ami-nations and insertions [100] have been reported as using nickel compounds. 

Trimethylsilyl)vinylketene (95) is stable and a reactive enophile in [4 + 2]cycloadditions. Trimethylsilylallenes have been used (Scheme 18) in the stereoselective synthesis of rra/t5-a,/3-unsaturated carbonyl compounds they have also been used to prepare the acetylenes (96) and (97) from ethylenic acylcyanides and carbonyl compounds/ respectively. In the presence of KF-18-crown-6, benzoyl trimethylsilanes (PhCOSiMea) behave as acyl anion equivalents in their reaction with organic halides to give ketones, ... 

Transition Metal-Catalyzed Reactions of Organic Halides with CO, Olefins, and Acetylenes R. F. Heck... 

Numerous metal-catalyzed reactions of organic halides with carbon monoxide and olefins, acetylenes, aldehydes, etc., have been carried out (21). Only two of these, however, appear to have been developed into generally useful reactions. One is the reaction of allylic halides with carbon monoxide and acetylene in alcoholic solution with a nickel catalyst (22,23). This reaction produces cis-2,5-hexadienoate esters at atmospheric pressure in good yields ... 

The ability of the ethynyl-l,5-azastibocines 5, to be used as alkynylation agents, has recently been demonstrated by Kakusawa et al. <2003TL8589>. The reaction of 5 with organic halides, such as acyl halides and aryl halides, in the presence of PdCl2(PPh3)2, as a catalyst, led to the formation of cross-coupling products, alkynyl ketones 109 and diaryl acetylenes 110, in good yields (Equations 9 and 10). 

The reaction occurs well below the temperature at which most of the parent metal carbonyls exchange with free CO and so is a direct nucleophilic attack on coordinated CO, although it may alternatively proceed via a prior electron path. The resulting acyl anions can be isolated as their [R4N] " or [ (C6H5)3P 2N] salts but are reactive and are used directly in subsequent alkylations with organic halides, acetylenes, a-/i-unsaturated carbonyls and alkyloxonium salts to form organic condensation products or metal-carbene complexes. 

Reaction of diphenyl diselenide or dimethyl diselenide with hydrazine hydrate and sodium hydroxide generates the corresponding selenolates smoothly in solvents like DMF or diethyl ether and in the presence of tetrabutylammonium chloride as a phase-transfer catalyst [13]. The selenolates react with organic halides to give various selenides (Scheme 9). Similar conditions have been applied to the synthesis of aryl vinyl selenides from diaryl diselenides and acetylene [14]. 

Heck RF. Transition metal-catalyzed reactions of organic halides with carbon monoxide, olefins, and acetylenes. Adv. Catal. 1977 26 323-349. 

B.ii. Cu-Catalyzed Cross-Coupling Reactions of Organic Halides with Terminal Acetylenes... 

Organocopper compounds make c/5-addition to a simple acetylene to afford the alkenylcopper compounds and further they react with organic halides to afford cis alkenes by a coupling reaction as shown in eq. (22.34) [82-85]. 

There are many other transition-metal catalyzed coupling reactions that are based on organic halides in aqueous media. One example is the coupling of terminal alkyne with aryl halides, the Sonogashira coupling, which has been discussed in detail in the chapter on alkynes (Chapter 4). An example is the condensation of 2-propynyl or allyl halides with simple acetylenes in the presence of copper salts. 

Copper(I) acetylides provide a useful route to the synthesis of a variety of organic acetylenic compounds and heterocycles, by reaction with aryl and other halides. A particularly important indirect use, where acetylides are probable intermediates, is the oxidative dimerization of acetylenes. A common procedure is to use the N, N,N, TV -tetramethylethylenediamine complex of CuCl in a solvent, or CuCl in pyridine-methanol, and oxygen as a reoxidant for Cu+ ... 

In early work, vinyl chloride had been heated with stoichiometric amounts of alkali alkoxides in excess alcohol as solvent, giving vinyl ethers as products (210). Supposedly this involved a Williamson ether synthesis, where alkali alkoxide and organic halide gave an ether and alkali halide. However, it was observed that small amounts of acetylene were formed by dehydrohalogenation of vinyl chloride, and that this acetylene was consumed as the reaction proceeded. Hence acetylene was substituted tor vinyl chloride and only catalytic amounts of alkali were used. Vinylation proceeded readily with high yields... 

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