1- Bromo-1-phenylethane preparation

Both methyltriethylphosphonium fluoride and methyltributylphospho-nium fluoride have been prepared The latter generates benzyl fluoride from benzyl chloride in 80% yield and ethyl fluoroacetate from ethyl bromoacetate in 53% yield Methyltnbutylphosphonium fluoride converts 1-bromododecane to a 50 50 mixture of 1-fluorododecane and 1-dodecene Methyltnbutylphosphonium fluoride also quantitatively forms styrene from 1-bromo-1-phenylethane [26] Methyl-tnbutylphosphonium fluonde is the reagent of choice for the conversion of N,N dimethylchloroacetamide to its fluoride, but it is not able to convert chloro-acetonitnle to fluoroacetomtrile Methyltnbutylphosphonium fluoride changes chloromethyl octyl ether to the crude fluoromethyl ether in 66% yield The stereoselectivity of methyltnbutylphosphonium fluoride is illustrated by the reac tions of the 2-tert-butyl-3-chlorooxiranes [27] (Table 2)... 

ANSWER Working backward, that is, using retrosynthetic analysis, we find that we can easily envision two syntheses of phenylacetylene. We can make phenylacetylene by dehydrohalogenation of 1,1-dibromo-l-phenylethane, which could have been prepared by allowing ethylbenzene (phenylethane) to react with 2 mol of NBS. Alternatively, we can prepare phenylacetylene from 1,2-dibromo-l-phenylethane, which could be prepared from styrene (phenylethene). Styrene can be made from 1-bromo-l-phenylethane, which can be made from ethylbenzene. 

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