Acetylene lithium compounds

Solutions of RC triple-bond C—Ti(0-/-C2H2)2 can be prepared by treating acetylenic compounds, such as phenylacetylene, with butyl lithium and then Cl—Ti(0-/-C2H2)2. These materials can react with aldehydes and epoxides to give the expected addition products (215). 

Ethynyl compounds react with sugar lactones to give acetylenic lactols (16,63). Reaction of 2,3-O-isopropylidene-D-ribonolactone (16a) with lithium acetylenic derivatives gave l-(2-substituted ethynyl)-2,3-0-isopropyli-dene-D-ribofuranoses. Similarly, treatment of 2,3 5,6-di-O-isopropylidene-L-gulono-1,4-lactone (9b) with various lithium acetylenic reagents gave... 

Lithium amide is used in synthesis of histamine and analgesic drugs. The compound also is used in many organic synthetic reactions including alkylation of ketones and nitriles, Claisen condensation, and in synthesis of antioxidants and acetylenic compounds. 

Diphenylacetylene has also been reacted with iodouracil 431 having a formamidine moiety under similar conditions to afford the dehydrogenated product 432 and the deaminated product 433 via intermediates 435 and 436, respectively. The selectivity increased in the presence of lithium chloride, whereby 93% of 432 with a trace amount of 433 were obtained. The lithium cation prevents the insertion of palladium into intermediate 434 to form intermediate 436, which is necessary to form 433. The reaction of 431 with asymmetric acetylenes in the presence of lithium chloride afforded the dehydrogenated pyridopyrimidines 437 and 439. However, reaction of 422 with acetylenic compounds in the absence of lithium chloride afforded the deaminated pyridopyrimidines 438 and 440 (Equation 37) <2000TL5899>. 

It is sometimes necessary to protect active sites of acetylenic compounds to achieve the desired reactions. Acetylenic compounds that have an active hydrogen tend to react with heavy-metal salts to form explosive metal acetylides. However, when treated with potassium mercuric tetraiodide or mercuric acetate in organic amines, monosubstituted terminal ethynyl compounds give stable crystalline mercuric salts. These mercuric salts can be purified by recrystallization in organic solvents and used for identification. They can be further converted to lithium acetylides, which are useful tools for chemical synthesis [Eq. (62) 156]. 

MERCURIO (Italian, Spanish) (7439-97-6) Violent reaction with alkali metals, aluminum, acetylenic compounds, azides, boron phosphodiiodide (vapor explodes), bromine, 3-bromopropyne, chlorine, chlorine dioxide, ethylene oxide, lithium, metals, methyl silane (when shaken in air), nitromethane, peroxyformic acid, potassium, propargyl bromide, rubidium, sodium, sodium carbide. Forms sensitive explosive products with acetylene, ammonia (anhydrous), chlorine, picric acid. Increases the explosive sensitivity of methyl azide. Mixtures with hot sulfuric acid can be explosive. Incompatible with calcium, sodium acetylide, nitric acid. Reacts with copper, silver, and many other metals (except iron), forming amalgams. 

The synthesis of the fragment C3-C13 was achieved in five steps from 169. Treatment of the tosylated stereotetrad 169 with 5 equivalents of lithium acetylide in DMSO led an acetylenic compound which was treated with ra-Buli and methyl iodide, and then reduced by Na/NH3 to produce the E-geometry of the C12-C13 double bond with concomitant removal of the PMB group at C5, giving the primary alcohol 170 (49% yield for the three-step sequence). Swern oxidation of 170 gave the corresponding aldehyde which was involved in an Evans-type asymmetric aldol reaction with the boron enolate A to produce the adduct 171 (dr > 95/5, 90% yield). (Scheme 33). 

EXPLOSION and FIRE CONCERNS noncombustible slightly volatile at ordinary temperatures NFPA rating (not rated) may explode on contact with 3-bromopropyne, ethylene oxide, lithium, peroxyfonnic acid, and chlorine dioxide vapor ignites on contact with boron diiodophosphide reacts violently with acetylenic compounds, metals, chlorine, chlorine dioxide, methyl azide, and nitromethane incompatible with acetylene, ammonia, chlorine dioxide, azides, calcium, sodium carbide, lithium, rubidium, and copper heating to decomposition emits toxic fumes of Hg use water spray, fog, or foam for firefighting purposes. 

Conversion of an acetylenic compound to a trans alkene is achieved with sodium or lithium and liquid ammonia though this reduction is not usually as simple as that using Lindlar s catalyst. Alternatively the cw-alkenes can be converted to raw5-alkenes by stereomutation (Section 10.9) and the trans isomer isolated from the equilibrium mixture by crystallization and/or silver ion chromatography. 

Of interest is the ( ,5 + C5) method in which the metalized acetylene compound (573) is coupled to the C5 aldehyde (574) to give the intermediate (575), which is converted to retinyl ethyl ether (576) by reductive elimination with lithium aluminum hydride (Makin, 1976). For analysis by gas chromatography,... 

Acetylenic compounds derived from aryl and heteroaryl aldehydes were further transformed into functionalized acetylenes in a one-pot reaction (eq 18). In the Colvin conversion of aryl or heteroaryl (oxo) acetates to aryl or heteroaryl propiolates, TMSC-(MgBr)N2 was found to be more efficient than its lithium salt (eq 19) ... 

Brooke GM, Quasem MA (1973) Partially fluorinated heterocyclic compounds. Part XI. The reactions of lithium pentafluorobenzenethiolate with acetylenic compounds giving benzo[fe] thiophen derivatives and/or olefins. 1 Chem Soc Perkin Trans 1 429-432... 

Okuhara, K. Introduction and Extension of Ethynyl Group using l,l-dichloro-2,2-Difluoroethylene. A Convenient Route to Lithium Acetylides and Derived Acetylenic Compounds. J. Org. Chem. 41, 1487 (1976). 

Lithium acetyhde also can be prepared directly in hquid ammonia from lithium metal or lithium amide and acetylene (134). In this form, the compound has been used in the preparation of -carotene and vitamin A (135), ethchlorvynol (136), and (7j--3-hexen-l-ol (leaf alcohol) (137). More recent synthetic processes involve preparing the lithium acetyhde in situ. Thus lithium diisopropylamide, prepared from //-butyUithium and the amine in THF at 0°C, is added to an acetylene-saturated solution of a ketosteroid to directly produce an ethynylated steroid (138). 

Sulfonium, cyclopropyldiphenyl tetrafluoroborate, 54, 28 Sulfonium salts, acetylenic, furans from, 53, 3 Sulfonium ylides, 54, 32 Sulfur, reaction with organo-lithium compounds, 50, 105 Sulfuryl chloride, with 1,1-cyclobutanedicarboxylic acid to give 3-chloro-l,1-cyclobutanedicarboxylic acid, 51, 73... 

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