Diyne Alcohols

Reduction of Diyne Alcohols with Lithium Alanate... 

The diyne alcohol is prepared by removal of the protecting group from C2H5OsCCH2CsCCH20CH(CH3)0C2H5 (see exp. 6.1). For the preparation of the protected alcohol compare p. 265. 

Zinc powder (30 g, Merck, analytical grade) is activated with dibromoethane (3.5 ml) in 100% ethanol (35 ml) as described in the previous experiments. After cooling to -30 C the protected diyne alcohol (0.10 mol), prepared as described in p. 213) is added in three equal portions over 5 min, while introducing N2- The temperature of the suspension rises fast and... 

Complexes of other metals are also capable of catalyzing useful carbonylation reactions under phase transfer conditions. For example, certain palladium(o) catalysts, like Co2(C0)g, can catalyze the carbonylation of benzylic halides to carboxylic acids. When applied to vinylic dibromides, unsaturated diacids or diynes were obtained, using Pd(diphos)2[diphos l,2-bis(diphenylphosphino)ethane] as the metal catalyst, benzyltriethylammonium chloride as the phase transfer agent, and t-amyl alcohol or benzene as the organic phase(18),... 

Various acetylenes having functional groups such as halide, alcohol, ether, amine, alkene and nitrile, are tolerated in the reaction. An asymmetric (2+2+2) cydoaddition of a,03-diynes with alkyne was achieved by a [IrCl(cod)]2 catalyst combined with a chiral phosphine ligand such as MeDUPHOS and EtDUPHOS, and gave axially chiral aromatic compounds [20]. 

From unsymmetrical propargyl alcohol and propargyl amine derivatives as coupling partners of diynes, the corresponding axially chiral alcohols and amines were obtained in almost perfect diastereo- and enantioselectivities (Scheme 11.13). 

In the majority of pentatetraenylidene complexes prepared or generated so far, the pentatetraenylidene ligand is derived from suitable C5 precursors. Usually penta-1,3-diynyl derivatives like the alcohol HC = C—C = C—CPh20H, its trimethylsilyl ether, or the 5,5,5-tris(dimethylamino)-substituted penta-l,3-diyne are employed. 

The bromination with alkali hypobromite in aqueous solution gives good results with (hetero)arylacetylenes, enynes (RCH=CHOCH) and diynes (RC=CC=CH) all acetylenes that are more acidic than those acetylenes in the aliphadc or cycloaliphatic series with an isolated triple bond. For the conjugated systems the hypobromite method is superior to the reaction of metallated acetylenes with bromine. Various acetylenic alcohols are also brominated smoothly, which can be explained in part by their better solubility in water. Since in the case of primary and secondary ethynyl alcohols, oxidation of the alcohol can occur, the use of an excess of hypobromite should be avoided. The best procedure is drop wise additon of a small shot measure of hypobromite ro a mixture of alcohol and water. If the bromoalkynes to be prepared are not too volatile, small amounts of THF or dioxane may be added to effect a better solubility of the alkyne in the aqueous phase. Addition of a co-solvent may also be desired when the starting compound is a solid (e.g. ethynylcyclohexanol). 

Reduction of an O-Protected Alcohol with a Conjugated Diyne System... 

Using this catalyst system for ring-closing alkyne metathesis, Fiirstner successfully synthesized ambrettolide and yuzu lactone from alcohol 125. " " Treatment of diyne 126a with Mo(CO)6 (5 mol%) and /i-chlorophenol (1 equiv.) in chlorobenzene at 140 °C leads to cycloalkyne 127a in 69% yield. Subsequent Lindlar reduction proceeds smoothly in a stereoselective manner to afford ambrettolide. Similarly, 126b affords cycloalkyne 127b in 62% yield. From this compound, yuzu lactone has been synthesized (Scheme 45). " " ... 

In the presence of base, alcohols and phenols add l,5-diphenylpenta-l,4-diyn-3-one (72JOU1398). At 40 °C addition occurs at both triple bonds to give a mixture of the 1,5-dialkoxy compound (411), the triketone and the pyran-4-one. On treatment with acid the former compounds are converted into the pyranone. However, at 15 °C only one triple bond is attacked giving the alkoxyvinyl ethynyl ketone (412), but this also forms the pyranone with acid (Scheme 136). 

Tris(dimethylamino)sulfonium difluo-rotrimethylsilicate, 336 Xenon(II) fluoride, 345 Alkyl bromides Potassium permanganate, 258 Sodium bromide, 46 Tetraethylammonium bromide, 46 Alkyl iodides Aluminum iodide, 17 Potassium permanganate, 258 Sodium iodide, 46 Tetraethylammonium iodide, 46 Alkynes (see also Acetylenic carbonyl compounds, Diynes, Enynes, Propar-gyl alcohols)... 

Zn (ZnBr2-K), H20, MeOH, THF (enyne, diyne, propargylic alcohol)... 

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