Acetylene lithium salt

By analogy, the acetylene aldehyde 500 gives, on addition of the chiral Li-enolate 501 [79-82], the chiral //-lactams 502 and 503 in 75% yield [80-82]. Similar (fhc-tam-forming reactions are discussed elsewhere [70, 83-88]. The ketone 504 affords, with the lithium salt of the silylated lithium amide 505, the Schiff base 506, in 74% yield (Scheme 5.27). The Schiff base 506 is also obtained in 25% yield by heating ketone 504 with (C6H5)3P=N-C6H4Me 507 in boiling toluene for 7 days... 

The facility with which the transfer of acetylenic groups occurs is associated with the relative stability of the ip-hybridized carbon. This reaction is an alternative to the more common addition of magnesium or lithium salts of acetylides to aldehydes. 

It would be ideal if the asymmetric addition could be done without a protecting group for ketone 36 and if the required amount of acetylene 37 would be closer to 1 equiv. Uthium acetylide is too basic for using the non-protected ketone 36, we need to reduce the nucleophile s basicity to accommodate the acidity of aniline protons in 36. At the same time, we started to understand the mechanism of lithium acetylide addition. As we will discuss in detail later, formation of the cubic dimer of the 1 1 complex of lithium cyclopropylacetylide and lithium alkoxide of the chiral modifier3 was the reason for the high enantiomeric excess. However, due to the nature of the stable and rigid dimeric complex, 2 equiv of lithium acetylide and 2 equiv of the lithium salt of chiral modifier were required for the high enantiomeric excess. Therefore, our requirements for a suitable metal were to provide (i) suitable nucleophilicity (ii) weaker basicity, which would be... 

By the extension of the above-mentioned stereoselective asymmetric addition of alkylithiums to other organolithium reagents such as lithium salts of methyl phenyl sulfide, 2-methylthiazoline, trialkylsilylacetylene, N-nitroso-dimethylamine, and acetonitrile, chiral oxiranes (95) U1), thiiranes (96) nl), acetylenic alcohols (98) 112), and amino alcohols (97) U1) were readily obtained. 

Kleinman and co-workers 20 synthesized a lactone precursor to the (2/ ,46, 56 )- -hydroxy-ethylene dipeptide stereoselectively in four steps using the lithium salt of ethyl propiolate as a homoenolate equivalent. As summarized in Scheme 11, addition of ethyl lithiopropiolate to a protected a-amino aldehyde affords hydroxy acetylenic esters as a mixture of dia-stereomers. Reduction of the acetylene group and subsequent lactonization gives a readily separable (4S)-lactone-enriched mixture. Direct alkylation with alkyl halide and lithium hexamethyldisilanazide yields the tram-lactone as the major stereoisomer. 

The lithium salt of ethoxy acetylene ha been found by Vollema and Arenszliquid ammonia, yielding 1,2-epoxy-6 ethoxy <4>pentync. The lithium salt of... 

The reacuons of electrophihc tnflyl sources with nucleophiles were investi gated The reaction of tnfhc anhydride with an organolithium reagent is not synthetically promising because of ditnflylation and other side reactions [20] When phenyllithium reacts with tnfhc anhydnde, dimerization products and acetylenic Michael diadducts are observed [20] (equation 17), but using the sodium salt of the alkynes instead of the lithium salt provides the alkynyl tnfluoromethyl sulfones [21] (equation 18) (Table 7) Alkynyl tnfluoromethyl sulfones are of synthetic interest, because they show a pronounced reactivity toward nucleophiles in addition reactions and cyclopentadiene in Diels-Alder reactions [21] (Table 7)... 

The usefulness of this lithium salt as an intermediate in organic synthesis has been recently extended by the reaction with acetylene and mono-substituted acetylenes (64). At — 70 C 2 moles of lithium salt add to 1 mole of acetylene to give, after hydrolysis, a high yield of 1,4-diketone. The same reaction carried out at — 30° C produces, in addition to the 1,4-diketone, a smaller yield of a y-lactone. 

A total synthesis of precalciferol (377) has been reported, which involved nucleophilic addition of the lithium salt (374) to the ketone (373), giving the acetylenic tricyclic intermediate (375). Elimination of HOCl from the chloro-hydrin (375) with bis(ethylenediamine)chromium(n) afforded the en-yn-ene (376), which was reduced to precalciferol (377) with Lindlar s catalyst. Thermal isomerization of (377) then afforded vitamin D3 (378). ... 

The potassium lithium salt of the aryl acetylene 170 was converted to a di-Grignard reagent with magnesium bromide [Eq. (75)]. Subsequent reaction of 170 with iodine and acidification afforded the acetylenic aryl iodide 171 [140]. 

Lithium acetylide can be prepared by heating LiH with excess dimethyl sulfoxide under argon at 70-75° to form the lithium salt of DMSO.5 A small amount of tri-phenylmethane is added and then acetylene is introduced until the red salt of tri-phenylmethyllithium disappears. Lithium acetylide is preferred to sodium acetylide in alkylation reactions with readily enolizable ketones. 

Peracid treatment of (108) then afforded the 14a-hydroxy-A -6-ketone which was cleaved by ozone to give the aldehyde (109). This aldehyde reacted with the lithium salt of the acetylenic ether (110) giving a mixture of products from which both the epimeric C-22 alcohols (111) and (112) were obtained. 

The lithium salt of 1-methylboratabenzene reacts with [TiCl3(THF)3] followed by magnesium powder in an atmosphere of carbon monoxide gives 43 (03AGE4510). The product reacts with acetylene in toluene to give a mixture of the products 44-46. Structural data for 45 point to the -borataoctacyclotetraene ligand. Similar reaction occurs between 43 and trimethylsilylacetylene to yield 47. 

The presence of lithium salt in the wastewater is avoided. Also, the waste-air streams conform with legal requirements and are all used either in the process or for energy production. Increased recycling of ammonia and acetylene leads to reduction in the consumption of ammonia to 25 % of its former value acetylene consumption is reduced by 50 %. Thus, the stoichiometric excess of acetylene used in stage I of the reaction is reduced to ca. 12%. 

Acetylene and ammonia, the gases, which are used in excess in this process, are almost completely recycled, the lithium salts are returned to the lithium metal manufacturer and there converted into the marketable lithium hydroxide. In the 1980s, the whole process was optimised to reduce the waste streams, and it was regarded as a classic example of an environment-friendly and economic production process. 

AU ethioIates and Selenolates. Sodium alkynethiolates are generated from 1,2,3-thiadiazoles (16) and reacted with CS2. Nucleophilic attack of sodium alkynethiolates to CS2 followed by the intramolecular cyclization proceeded to give 1,3-dithiole-2-thiones (17) in 57-98% yields (eq 2)P Lithium alkynethiolates, which are derived from terminal acetylenes, BuLi, TMEDA, and elemental sulfur, can also be used in this cyclization reaction (eq 13). In the case of the lithium salts, CS2 is added at —90 °C, and the reaction mixture is quenched by adding water containing THF at this temperature to lead to (17). Lithium alkyneselenolates participate in this type of transformation (eq 14). The reaction mixture is quenched with alkyl thiocyanates or a combination of elemental selenium and alkyl iodides to give 1,3-selenothiole-2-thiones (18) in 80-98% yields. The reaction is quenched in a similar manner to that from the lithium alkynethiolates. ... 

Methyl trichloroacetate reacts with olefins in the presence of transition-metal catalysts to give mixtures of the corresponding butyrate and y-butyrol-actone. Substituted y-butyrolactones are produced in the radiation-induced addition of alcohols or the electrochemical reductive addition of acetone to a/3-unsaturated esters. Acetylenic Grignard reagents react with y-lactones to give products of double addition, whereas the analogous lithium salts react only once. The products observed in the pyrolysis of y-lactone toluene-/ -sulphonylhydrazone sodium salts can be accounted for by the intermediacy of an oxycarbene. ... 

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) ... 

Several new syntheses of vinylsilanes have been described. Tris(trimethyl-silyl)aluminium undergoes 5yn-addition to alkynes alternatively the same -isomers can be obtained by photochemical isomerisation of Z-1-alkenyl-silanes. Other methods described involve treatment of the lithium salts of hydrazones with trimethylsilyl chloride, Wurtz-type coupling with vinyl bromides, and reaction of acetylenes with a silyl-copper reagent followed by an electrophile. Using the hydrazone method, a route has been devised for 1,2-carbonyl transposition within ketones (Scheme 17). ... 

Negishi and coworkers have developed a method for preparation of conjugated -enynes via alkenylboranes. In one synthesis (227), acetylene (50i) was treated with disiamylborane and then with the lithium salt of acetylene (503) to afford complex (504), which after treatment with iodine and sodium hydroxide stereoselectively afforded (505) (Scheme 88). Syntheses of other conjugated E,Z dienes have been achieved by this method (228, 229). By use of thexylborane and 1-bromo-l-alkynes, conjugated E,E dienes can be readily prepared (230) (Scheme 89). 

Low yields of a mixture of cis- and trons-acetylenic thiirans (18) were obtained by treatment of lithium salts of 2-propargylthiothiazolines (17) with benzaldehyde. A mechanism was proposed. Thiiran was proposed as a product, although not identified, in the reaction of oxiran with 3-/3-hydroxyethylthio-1,2,4-triazoles (19) to yield N-/3-hydroxyethyltriazo-linones (20). ... 

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