Butylacetylene

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Addition of n butyl bromide then gives M-butylacetylene (1-hexyne) ... 

Pentyn-l-ol. Prepare a solution of sodamide in liquid ammonia as detailed for n-Butylacetylene. Use a 3-htre three-necked flask, equipped with a Dewar type of reflux condenser (Fig. II, 1, 4, h) cooled with Dry Ice... 

To a mixture of 0.40 mol of neohexene ( commercially available) and 200 ml of dry diethyl ether 0.35 mol of bromine was added with cooling between -40 and -50°C. The diethyl ether and excess of neohexene were then completely removed by evaporation in a water-pump vacuum.In the second flask was placed a solution of 90 g of commercial KO-tert.-C9H9 (see Chapter IV, Exp. 4, note 2) in 250 ml of DMSO. The dibromo compound was added in five portions during 15 min from the dropping funnel after the addition of each portion the flask was swirled gently in order to effect homogenization. Much heat was evolved and part of the tert.-butylacetylene passed over. After the addition the flask was heated for 30 min in a bath at B0-100°C. 

Reactions of acetylene and iron carbonyls can yield benzene derivatives, quinones, cyclopentadienes, and a variety of heterocycHc compounds. The cyclization reaction is useful for preparing substituted benzenes. The reaction of / fZ-butylacetylene in the presence of Co2(CO)g as the catalyst yields l,2,4-tri-/ f2 butylbenzene (142). The reaction of Fe(CO) and diphenylacetylene yields no less than seven different species. A cyclobutadiene derivative [31811 -56-0] is the most important (143—145). 

Later a more convenient synthesis of 172 appeared heating di-ferf-butylacetylene with elemental sulfur in benzene at 190°C in an autoclave... 

Vinyl cations also have been invoked as intermediates in the reaction of HCl with r-butylacetylene (49). With neat mixtures in the liquid phase at ambient temperatures, the following four products were observed ... 

Butane, 1,4-diiodo-, 30, 33 2-Butanone, 3-acetamido-, 33,1 n-BuTYLACETYLENE, 30, IS tert-Butyl alcohol, 30, 19, 20 32, 20 ierl-Butylbenzene, 32, 91 n-Butyl bromide, 30, 16 tert-Butyl hypochlorite, 32, 20 n-Butyl iodide, 30, 34 Butylketene dimer, 31, 71 -ter -Butylphenyl salicylate, 32, 26 Butyrchloral, 33, IS Butyric acid, a, y-dicyano-o-phenyl-, ethyl ester, 30, 80... 

Platinum on carbon did almost exactly the same thing but required a temperature of about 100°C to do so. With excess acetylene, only III formed. With tcrt-butylacetylene no II formed, probably because of steric hindrance, but I and III formed readily. 3-Hexyne reacted more slowly, required heat with chloroplatinic acid, and formed exclusively c/s-3-di-chlorosilyl-3-hexene. Trichlorosilane with platinum on carbon also added (57) to 1-alkynes or to phenylacetylene exclusively by cis addition to give only trans adducts. Later works (55) indicate that chloroplatinic acid and other soluble catalysts also give exclusively cis addition with a wide variety of Si—H compounds. 

Most of these catalytic systems are able to dimerize either aromatic alkynes, such as phenylacetylene derivatives, or aliphatic alkynes, such as trimethylsilylacetylene, tert-butylacetylene and benzylacetylene. The stereochemistry of the resulting enynes depends strongly on both the alkyne and the catalyst precursor. It is noteworthy that the vinylidene ruthenium complex RuCl(Cp )(PPh3)(=C=CHPh) catalyzes the dimerization of phenylacetylene and methylpropiolate with high stereoselectivity towards the ( )-enyne [65, 66], and that head-to-tail dimerization is scarcely favored with this catalyst. It was also shovm that the metathesis catalyst RuCl2(P-Cy3)2(=CHPh) reacted in refiuxing toluene with phenylacetylene to produce a... 

The head-to-head dimerization with formation of a butatriene derivative was very scarcely observed as the main catalytic route (Scheme 10.19, cycle B). Nevertheless, this was the case with benzylacetylene in the presence of RUH3CP (PCy3) as catalyst precursor in tetrahydrofuran at 80°C which gave more than 95% of (Z)-l,4-diben-zylbutatriene [66], and with terf-butylacetylene with two efficient catalytic systems capable ofgenerating zero-valent ruthenium species, RuH2(PPh3)3(CO) and Ru(cod) (cot) in the presence of an excess of triisopropylphosphine, which led to (Z)-l,4-di-tert-butylbutatriene as the major compound [71-73]. 

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