Methylene (CAS NO.: ), which is also known as Cyclohexane, methylene-, could be produced through the following synthetic routes.

A. Triphenylmethylphosphonium bromide (CAS NO.: ). A solution of 55 g. (0.21 mole) of triphenylphosphine dissolved in 45 ml. of dry benzene is placed in a pressure bottle, the bottle is cooled in an ice-salt mixture, and 28 g. (0.29 mole) of previously condensed methyl bromide is added. The bottle is sealed, allowed to stand at room temperature for 2 days, and is reopened. The white solid is collected by means of suction filtration with the aid of about 500 ml. of hot benzene and is dried in a vacuum oven at 100° over phosphorus pentoxide. The yield is 74 g. (99%), m.p. 232–233°.

B. Methylenecyclohexane (CAS NO.: ). A 500-ml. three-necked round-bottomed flask is fitted with a reflux condenser, an addition funnel, a mechanical stirrer, and a gas inlet tube. A gentle flow of nitrogen through the apparatus is maintained throughout the reaction. An ethereal solution of n-butyllithium2 (0.10 mole, about 100 ml., depending on the concentration of the solution) and 200 ml. of anhydrous ether is added to the flask. The solution is stirred and 35.7 g. (0.10 mole) of triphenylmethylphosphonium bromide is added cautiously over a 5-minute period. The solution is stirred for 4 hours at room temperature.

Freshly distilled cyclohexanone (10.8 g., 0.11 mole) is now added dropwise. The solution becomes colorless and a white precipitate separates. The mixture is heated under reflux over-night, allowed to cool to room temperature, and the precipitate is removed by suction filtration. The precipitate is washed with 100 ml. of ether, and the combined ethereal filtrates are extracted with 100-ml. portions of water until neutral and then dried over calcium chloride. The ether is carefully distilled through an 80-cm. column packed with glass helices. Fractionation of the residue remaining after removal of the ether through an efficient, low-holdup column gives 3.4–3.8 g. (35–40%) of pure methylenecyclohexane, b.p. 99–101°/740 mm., n_D25 1.4470.