Allenes acetylene derivative

Ph3SnCl and propargylmagnesium bromide give a 90 10 mixture of the acetylenic and allenic tin derivatives, while in the case of Me3SnCl this ratio is 30 70 . 

High yields of -substituted allenic primary amines 227 are obtained by the CuBr-Me2S-or NiCh Ph2PCH2CH2CH2PPh2-catalysed reaction of the acetylene derivative 226 with aryl Grignard compounds and subsequent deprotection by flash chromatography219. 

Investigations of base-catalyzed isomerizations of allene derivatives have been recently continued. For instance, the rearrangement of allene ethers 53 under superbasic conditions (KOH-DMSO) is considered as one of the steps in hydration of acetylene derivatives (equation 17)31,32. 

Potassium 3-aminopropylamide [56058-00-7] (KAPA), KNHCH2CH2CH2-NH2, pKa = 35, can be prepared by the reaction of 1,3-diaminopropane and potassium metal or potassium hydride [7695-26-7] (57—59). KAPA powder has been known to explode during storage under nitrogen in a drybox, and is therefore made in situ. KAPA is extremely effective in converting an internal acetylene or allene group to a terminal acetylene (60) (see ACETYLENE-DERIVED chemicals). 

Oxidation of pentynediol 119 by Mn02 followed by interaction with p-TSA led to acetylenic derivative 120 that possesses extremely strong and diffusive violet and freesia, raspberry, woody, odors similar to )S-ionone. But the odor of allene derivative 122, also prepared from diol 119 by dehydration with LiAIH4 and further oxidation with Mn02, was rather unpleasant (85LA950). 

Sequential treatment of an ethynylalkanol acetate with butyllithium and a trialkyl-borane produces an allenic borane (23), which when protonated with acetic acid forms an allene, while upon treatment with water affords an acetylene derivative, presumably via a cyclic process (Eq. 51) A novel synthesis of homopropargylic... 

In the following steps (eq 7), we observed two HCl-catalyzed processes an acetylenic-allene rearrangement (to 10) and an allenic-acetylene rearrangement (to 11). While both 10 and 11 were easily identified by their characteristic NMR signals and could be distilled as a mixture without decomposition, only the final acetylene derivative (11) could be isolated in pure form after fractional distillation. Propargyl bromide reacted similarly with the three-coordinate phosphine, but in this case all of the chemical transformations occurred very rapidly and only the final acetylene phosphoranimine (11) could be isolated. 

Methanol and propan-2-ol add non-stereospecifically to cholest-4- and -5-ene as do ethylene and tetrafluoroethylene to 3 -acetoxypregna-5,16-dien-20-one although only 16a,17a-addition products were isolated from allene, acetylene, and dichloroethylene the derived 20-anti-oxime isomerises to the syn-isomer on irradiation in THF and cyclises internally in benzene solution. Irradiation of the trans-acid (561) in methanol resulted only in a cis-trans equilibration, although the trans-acid (562) produced the unsaturated lactone (563). 

Precursors for an allene oxy-Cope variant are readily prepared from acetylenic derivatives. Rearrangement of allenic alcohol 11 yields a 1 1 EjZ mixture of 121108. 

In principle, the reaction of terminally lithiated allenes with electrophilic reagents may give both the allenic and the acetylenic derivative ... 

However, the reaction with carbonyl compounds of the a-Grignard or a-zinc halide derivatives (prepared by exchange) affords mixtures of the allenic and acetylenic derivatives [9] ... 

Subsequent interaction with electrophilic reagents in general yields a mixture of the allenic and the acetylenic derivative trimethylsilylation and alkylation, however, seem to afford the y-functionalized allenic ether [99]. Under strongly polar conditions, i.e. if lithium is replaced by potassium (by addition of t-BuOK) and HMPT is added as co-solvent, the y-metallated allenic ethers rearrange into the a-metallic derivatives [100]. This remarkable isomerization may take place via a head-to-tail arrangement of two metallated molecules ... 

Potassium tert-butoxide Allenes from acetylene derivatives... 

Interesting variations of potential synthetic utility include the use of a-acetylenic epoxides and a-allenic alcohol derivatives. " The latter, which can be obtained from the former, have been converted to conjugated dienes for use in the Diels-Alder and other reactions (Scheme 33). 

Condensation of y-(trialkylsilyl)allylboranes and allenylboranes with simple aldehydes and conjugated allenic, acetylenic, and enynyl aldehydes followed by a stereoselective elimination of trialkylsilanol produced 1,3-butadienes, diene-allenes, enyne-allenes, enediynes, and dienediynes with high isomeric purity. The trimethyltin chloride-induced transformations of 1-alkynyltrialkylborates also provided easy access to a variety of unsaturated compounds. High energy intermediates, such as o-isotoluenes, biradicals, o-quinodimethanes, benzocyclobutadienes, and enyne-ketenes, were derived from these unsaturated molecules for subsequent synthetic elaborations. 

Dehydrohalogenation with fluoride ion Acetylene derivs. and allenes from a,/ -ethylenehalides... 

Bromo-l-p-nitrophenylpropene heated 10-20 min. at 100° with KF in dimethyl sulfoxide -> acetylene deriv. Y 94%. allene deriv. Y 93%. 

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