Ammonia → Cyclohexane, 2-propynylidene-

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Reaction Steps

To a solution of 0.7 mol of sodium amide in about 700 mL of liquid ammonia was added 1-(1-propynyl)cyclohexene (0.50 mol) dropwise over 15 min with efficient stirring. A fine, white suspension of the potassium alkynylide was formed gradually. After 2 h, 200 mL of Et2O was added over a few minutes. The flask was then placed in a water bath at 40° C. When the stream of ammonia vapor had become faint, introduction of nitrogen (~500 mL/min) was started. An additional volume of 100 mL of Et2O was added. The flask was placed in an ice-water bath and ice water (~300 mL) was added to the reaction mixture over about half an hour with vigorous stirring. After dissolution of all solid material, the layers were separated and the aqueous layer was extracted twice with small portions of Et2O. The combined organic solutions was dried over MgSO4. Propynylidenecyclohexane (b.p. 55° C./10 mm Hg) was obtained in excellent yield by concentrating the ethereal solution in a water-pump vacuum (bath temperature not higher than 35° C.) and subsequently distilling the remaining liquid thorough a 30-cm Vigreaux column.

Provenance & Evidence