Phenylethyne-, sodium

Sodium Pbenylethynetellurolate5 An apparatus suitable for work with liquid ammonia under a nitrogen atmosphere is set up. A 500-m/flask is charged with 250 ml of liquid ammonia freshly distilled from sodium. In the liquid ammonia are dissolved 1.15 g (0.05 mol) of sodium, a catalytic amount of iron(III) nitrate is added, and 5.1 g (0,05 mol) of phenylacetylenc are added dropwise over 0.5 h to the sodium amide solution. The mixture is allowed to stand for 40 min and then 6.4 g (0.05 mol) of finely powdered tellurium arc added to the sodium acetylide solution. The ammonia is evaporated and the residue of sodium phenylethyne-tellurolate can be dissolved in an appropriate solvent for further reactions. 

The reaction of tellurium with sodium phenylacetylide produced sodium phenylethyne-tellurolate that formed, on reaction with dimethyl acetylenedicarboxylate via cycloaddition, 2,3-bis[methoxycarbonyl]-4-phenyltellurophene as one of the tellurium-containing products2. The tellurophene derivative was separated and purified by chromatography on silica gel. 

Dibenzylidene-l, 3-ditelluretane was prepared by reacting tellurium with sodium phenylacetylide and acidifying the resulting mixture, which contains sodium phenylethyne-tellurolate, with hydrogen chloride in diethyl ether The structure of the compound was confirmed by single crystal X-ray analysis . The earlier reported formulation of this compound as 2-benzylidene-4-phenyl-l,3-ditelluracyclopent-4-ene is incorrect. ... 

A new synthesis of 2,4,4,6-tetramethyl-4//-l,3-oxazine (155) simply involves a reductive cycloaddition of 4-methylpent-3-en-2-one and acetonitrile in the presence of trimethylsilyl chloride and sodium iodide (Scheme 42) <89TL4741>. Other cycloaddition reactions have been used previously to synthesize 4//-l,3-oxazines and this methodology has been extended to include cycloadditions between alkynes and l-oxa-3-azabuta-1,3-dienes. For example, phenylethyne and the A-benz-oylimine (156) afford 4,4-bis(trifluoromethyl)-2,6-diphenyl-4//-l,3-oxazine (157). The reaction proceeds through a Michael-type addition between the alkyne and the heterodiene giving an adduct which when heated to 80-90°C cyclizes to the oxazine (Scheme 43) <83CC945,89ZN(B)1298>. 

Elimination reactions can also be used to prepare alkynes. Dihalides can be converted into alkynes by treatment with base, provided that the two halogen atoms are on the same, or adjacent, carbon atoms. In general, alkyne formation requires more drastic reaction conditions than alkene formation, and a strong base, such as sodium amide, is usually employed (Reactions 5.4 and 5.5). The product of Reaction 5.5, phenylethyne, is shown in Figure 5.1 as a ball and stick model. 

Draw the final product when 4-methylpent-l-en-3-one reacts (a) with sodium cyanide and is hydrolyzed, and (b) with the sodium salt of 2-phenylethyne followed by hydrolysis. 

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