Alkynes Aluminum halides

Alkenes, Cyclic Alkenes, and Dienes Alkenes, Cyclic Alkenes, and Dienes Ethylene Propylene Alkyl Halides Alkynes Aluminum Americium Amides Amides Carbofuran Dimethyl Acetamide Amines Antimony... 

The A1—C bond in the halomethylalanes, in addition to the carbon-halogen bond, is highly reactive. Dialkyl halomethylalanes react with alkenes or alkynes even at room temperature with addition of the A1—C bond (route A, below) to the C=C double bond or the C=C triple bond. Addition of the C—X bond (route B) is also possible, but has not yet been demonstrated with certainty. The resulting 3-halogenoalkyl alanes are unstable under the conditions of their formation and decompose to cyclopropane or cyclopropene and aluminum halide (27, 98) ... 

An example of addition of sulfenyl halides to an alkyne is shown in Scheme 1928 where the initial trans adduct of 1,4-dichlorobut-2-yne is further transformed by treatment with base or aluminum amalgam. Another example involves boron trifluoride-catalyzed addition of an arenesulfenamide to alkynes in the presence of acetonitrile, giving (3-acetamidinovinyl sulfides (Scheme 20),29 which can be hydrolyzed to (3-keto phenyl sulfides.30... 

Several of the trialkylaluminum and alkylaluminum halides and hydrides mentioned above are commercially available. Alkynyl, alkenyl, cyclopentadienyl, and aryl derivatives are, in general, not commercially available and must be synthesized for laboratory use. Alkynyl derivatives can be prepared by salt metathesis, as in the reaction of Et2AlCl with NaC=CEt to give Et2AlC=CEt. The acidity of terminal alkynes is sufficient for preparation of alkynyl aluminum compounds by alkane or hydrogen elimination upon reaction with a trialkylaluminum or an aluminum hydride (equation 17), respectively. TriaUcynyl aluminum compounds are typically isolated as Lewis base adducts to stabilize them against otherwise facile polymerization. Alkenyl compounds of aluminnm have similarly been prepared. 

Diallenyltin dibromide, prepared by treatment of propargyl bromide with metallic tin in the presence of metallic aluminum in dry tetrahydrofuran, reacts with aldehydes and ketones to afford 3-alkynic alcohols selectively (Scheme 4). This result is different from a previous report in which an a-allenic alcohol was found to be a major product from a propargyltin reagent prepared from a tin(II) halide. " On the other hand, -alkynic and a-allenic alcohols were synthesized selectively by the reaction of aldehydes and ketones with bis(trimethylsilylpropargyl)tin diiodide using different solvent systems (Scheme S). "... 

With chloroacetyl chloride and aluminum chloride, addition of chloride gave the P-chloro-a-silyl enone in addition to the alkynic ketone. Addition of halide has also been observed in alkynations of 2-alkoxy-1 -trimethylsily lethynes. ... 

There are several alternative methods for the formation of acylsilanes these include the reaction of silyl cuprates with acid halides, palladium-assisted coupling of acyl halides with hexamethyldisilane, the reaction of thiopyridyl esters with tris(trimethylsilyl)aluminum in the presence of Cu salts, and the hydroboration of trimethylsilyl-substituted alkynes. While all of these procedures are complementary, the method involving the title corqtound provides an easy, inexpensive route to acylsilanes. 

R = MeO, BuO, tPr2N) in 40-81% yields. Ethylene was either supplied to the reaction mixture as the gas or generated in situ from 1,2-dihaloethane and magnesium. The cross intermolecular cycloalumination of cyclic 1,2-dienes or alkynes and ethylene with aluminum aUcyl halide derivatives in the presence of Zr and Ti complexes furnishes unsaturated bicyclic aluminacyclopentanes or alumina-cyclopentenes as well as the corresponding 1,4-dialuminum compounds in fairly high yields (Scheme 34). 

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