Lithium acetylides, oxygenation

The monolithium salt of 4-hydroxy-4-(phenylethynyl)-2.5-cyclohexadienone (12), prepared in situ by the addition of lithium acetylide to /7-benzoquinone, was treated with methylmagnesium chloride in l HF-TMEDA or in THF —DMPU. The syn-, 4-addition adduct 13, derived from intramolecular delivery of the carbon nucleophile by the hydroxy oxygen, as well as the <7s-1,4-diol 14, obtained via intermolecular 1,2-addition, were obtained in varying amounts depending on the conditions. The selectivity on 1,4- to 1,2-addition increased by the addition of cation chelating agents such as DMPU, TMEDA, and 15-crown-5. Although the 1,4 to 1,2... 

Allyltributyltin, 10 Vinyltrimethylsilane, 343 Homoallylic ethers Allyltrimethylsilane, 11 Crotyltrimethylsilane, 86 Trityl perchlorate, 339 Homopropargylic alcohols Allenylboronic acid, 36 D imethoxy [ 1 -trimethylsilyl-1,2-buta-dienyljborane, 218 Lithium acetylide, 44 Triisopropoxy[l-(trimethylsilyl)-l,2-buta-dienyl]titanium, 218 Hydroperoxides Oxygen, singlet, 228 Hydroxy acids a-Hydroxy acids... 

Oxygenation of lithium acetylides with lithium t-butylperoxide. 745... 

Lithium acetylides 28 are oxygenated by lithium t-butylperoxide, prepared from anhydrous t-butylhydroperoxide and LHMDS, to give lithium ynolates 29 (equation 9) °. This method has been used as an efficient route for the preparation of the silyl ynolates 30" (Section V). Dioxygen, t-butyl perborate and bis(trimethylsilyl)peroxide have been unsuccessful as oxidation reagents " . ... 

IODINE (7553-56-2) A powerful oxidizer. Material or vapors react violently with reducing agents, combustible materials, alkali metals, acetylene, acetaldehyde, antimony, boron, bromine pentafluoride, bromine trifluoride, calcium hydride, cesium, cesium oxide, chlorine trifluoride, copper hydride, dipropylmercury, fluoride, francium, lithium, metal acetylides, metal carbides, nickel monoxide, nitryl fluoride, perchloryl perchlorate, polyacetylene, powdered metals, rubidium, phosphorus, sodium, sodium phosphinate, sulfur, sulfur trioxide, tetraamine, trioxygen difluoride. Forms heat- or shock-sensitive compounds with ammonia, silver azide, potassium, sodium, oxygen difluoride. Incompatible with aluminum-titanium alloy, barium acetylide, ethanol, formamide, halogens, mercmic oxide, mercurous chloride, oxygen, pyridine, pyrogallic acid, salicylic acid sodium hydride, sodium salicylate, sulfides, and other materials. 

An enolate anion is a nucleophile and, unlike Grignard reagents and organolithium reagents, reacts easily with the electrophilic carbon of an alkyl halide. Although both the oxygen and the carbon are nucleophilic (sec. 9.3.B), the carbon is usually the most nucleophilic site in the enolate. As with other carbon nucleophiles, such as acetylides (sec. 8.3), the electron rich carbon attacks the electrophilic carbon of the halide to form a new carbon-carbon bond, with lithium iodide (Lil) as the byproduct. 

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