1-Diethylaluminum alkynes

Alkynyldiethyl alanes. Alkynyldiethyl alanes, also known as 1-diethylaluminum alkynes (3), are readily prepared1 by conversion of a terminal alkyne (1) in toluene solution into the lithium derivative (2) with n-butyllithium in hexane. Addition of a 20 % solution of diethylaluminum chloride in toluene leads to formation of the reagent (3) in solution with precipitation of LiCl. 

Electron-rich 3-methoxy-4-trimethylsilyl-l,2-butadiene (22) reacted with several electron-poor alkenes in the presence of diethylaluminum chloride to afford methylene cyclobutanes 23. Reactions with alkynes were performed in the presence of methylalu-minum bis(2,4,6-tri-t-butylphenoxide) (equation 7)16. 

On treatment with diethylaluminum trimethylsilylacetylide in the presence of BF3 OEt2, a-acetoxy ether 94 gave the rran5-l,3-dioxane 95 in good yield with excellent stereoselectivity, as reported by Rychonovsky and Dahanukar [91]. The trans alkyne adduct has the configuration expected from axial addition to a cyclic oxonium ion (Sch. 59). 

Homo-Diels-Alder reactions occur between norbornadiene and norbornene or unactivated alkynes giving 14 and 15a-e , respectively, by using as catalyst the cobalt complex obtained by reducing tris(acetylacetonato)cobalt with diethylaluminum chloride in the presence of bis(l, 2-diphenylphosphino)ethane." ... 

The reaction of a,p-alkynic ketones with diethylaluminum iodide gives allenolates by 1,4-addition (Scheme 35).125 These intermediates can react with aldehydes to give aidoi-type products. 

Reactions with Epoxides. These reactions allow preparation of /3-alkynic alcohols (eq 4) the use of -butyllithium, followed by diethylaluminum chloride, may increase the yield. 

Harrity exploited the carbocation stabilizing ability of cobalt-alkyne complexes to promote a novel O C rearrangement reaction. Exposure of cyclic enol ether 23 to diethylaluminum chloride promotes ionization of the C-O bond to yield the stabilized carbocation and an enolate. Bond rotation followed by C-C bond formation provides cyclohexanone product 24. ... 

Formation and Reaction of Alkynylaluminum Reagents. Lithium acetylides react with Me2AlCl to give dimethylaluminum acetylides that react analogously to the more commonly used diethylaluminum acetylides (see Diethylalu-minum Ethoxyacetylide). Addition of the aluminum acetylide to propiolactone results in an Sn2 reaction to give an alkynic acid (eq 1) ... 

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