A. Ethynylmagnesium bromide. A 500-ml. three-necked flask, equipped with a sealed mechanical stirrer, a reflux condenser, and a pressure-equalized dropping funnel, is arranged for carrying out a reaction in an atmosphere of nitrogen by fitting into the top of the condenser a T-tube attached to a low-pressure supply of nitrogen and to a mercury bubbler. For later use there is also prepared a dry 1-l. three-necked flask equipped with a sealed mechanical stirrer, a gas inlet tube which will dip below the surface of 200 ml. of liquid in the flask, a 500-ml. dropping funnel, and a gas outlet protected by a calcium chloride drying tube.

The 500-ml. flask is dried by warming with a soft flame as a slow stream of nitrogen is passed through the system. A solution of ethylmagnesium bromide is prepared in this flask from 12 g. (0.5 g. atom) of magnesium turnings, 60 g. (0.55 mole) of ethyl bromide (dried over calcium chloride), and 300 ml. of tetrahydrofuran (Note 1) and (Note 2).

After the preparation of ethylmagnesium bromide is completed, the separatory funnel is replaced by a bent tube which reaches the bottom of the flask and is bent at the outer end for downward delivery (Note 3). The warm (40–50°) solution is forced under nitrogen pressure (by carefully pinching off the tube to the mercury bubbler) into the 500-ml. separatory funnel which has been prepared for attachment to the 1-l. flask. After all the solution has passed into the separatory funnel, nitrogen flow is allowed to continue briefly in order to displace the air above the solution, then the funnel is stoppered loosely and attached to the 1-l. flask. Two hundred milliliters of purified tetrahydrofuran is now placed in the flask, acetylene (Note 4) is introduced through the gas-inlet tube at the rate of 15–20 l. per hour, and the stirrer is started. After 5 minutes, about 5 ml. of the solution of ethylmagnesium bromide is added in 1 portion. Almost at once, there appears a froth of ethane which is easily distinguishable from the larger bubbles of acetylene. When the frothing subsides, portionwise addition of the ethylmagnesium bromide solution is continued until the total solution has been added. This requires about 3 hours, and the temperature of the reaction rises 5–10° above room temperature. The solution of ethynylmagnesium bromide is homogeneous at 30° (Note 5).

B. 1-Phenyl-1-penten-4-yn-3-ol. The stirred solution of ethynylmagnesium bromide is cooled in ice water as there is added dropwise during about 45 minutes a solution of 47.5 g. (0.36 mole) of freshly distilled cinnamaldehyde (Note 6) in 50 ml. of purified tetrahydrofuran. After addition is complete, stirring is continued overnight as the solution is allowed to warm to room temperature. The brown homogeneous reaction mixture is added carefully to 1.5 l. of cooled saturated ammonium chloride solution, then the aqueous phase is extracted with three 250-ml. portions of ether. The ether extracts are combined with the tetrahydrofuran solution and dried over anhydrous magnesium sulfate. After evaporation of the solvent, the product is distilled (Note 7) at a pressure of about 0.1 mm., with the heating bath at about 90°. The distillate, which solidifies on cooling, is crystallized from petroleum ether (b.p. 40–60°) to yield 33–39 g. (58–69%) of the unsaturated alcohol of m.p. 67–68° (Note 8).