1-phenylprop-l-yne

A mixture containing 3,3,3-trifluoro-1-phenylprop-l-yne (4 5.00 mmol), PhSH (5.00 mmol), and t-BuOK (50 mg) in absolute EtOH (15 mL) was maintained at 25 C for 6h under Nj. The mixture was then poured into H,0 and extracted with EtjO. The Et,0 solution was washed with dil aq NaOH and 11,0. and dried (MgSO ). Removal of the drying agent and solvent left a residue which was chromatographed on silica gel (no solvent given) to afford pure 5 yield 1.29g (92%). 

The spectroscopic data for 9 support the proposed structure. In particular, the wSi NMR chemical shift of 5 43.19 as a triplet (Jsi-p(C/ ) = 40.11 Hz) resembles the literature value reported for the m-NiSijPC complex. 3 Compound 9 was found to be a good reactive intermediate for the double silylation reaction. The reaction of 1 with 1-phenylprop-l-yne (1 equiv) in the presence of a catalytic amount of 9 (0.03 equiv) for 6 h afforded the double-silylated producted 10 in 94 % (GC) yield. The reaction was quite sensitive to the reaction conditions. When the same reaction was carried out at higher temperature (70-75 °C), the major component was identified as the acetylene cyclotrimerization product 11 (Scheme 2), which has been characterized by spectroscopic techniques. When hex-l-yne is employed as a terminal alkyne in the reaction with 1 under the same condition, the five-membered disilyl ring compound 12 is isolated as a colorless liquid in 71 % yield. 

A direct approach to silacyclobutane (siletane) derivatives is the reaction of meth-ylsilenes with other unsaturated compounds. Thus, the silaethylene (silene) (326), formed from pivaloyl-tris(TMS)-silane (325) via thermolysis (10h/140°C), reacts with 1-phenylprop-l-yne to yield the silacyclobutene (silete) derivative 327 (equation 148)172. 

The regiospecific formation of the cyclobutene-type adduct (261) has been reported as a result of the photoaddition of diphenylacetylene to the cyanouracil (262). The cycloaddition of 1-phenylprop-l-yne to the same substrate is reported to yield the cyclobutene (263) as the main product when Pyrex-filtered irradiation is used. The irradiation of the same compounds using 254 nm light afforded the novel adduct (264), presumably formed by the secondary cyclization of the initially produced adduct (265). Indeed the sensitized irradiation of the uracil (262) and the propyne yields this adduct (265) as a Z- -mixture as well as the cyclobutene (263). Direct irradiation of (265) affords the cyclized compound... 

Dehydrobromination of 2,3-dibromo-l,l,l-trifluoro-3-phenylpropane (30) and 2-bromo-3,3,3-trifluoro-l-phenylprop-l-ene (31) leads to 3,3,3-trifluoro-1-phenylprop-1-yne (32).62... 

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