Triphenylmethylphosphonium bromide

A. Triphenylmethylphosphonium bromide. 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 (Note 1). 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. 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 -butyllithium (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 (Note 2). The solution is stirred for 4 hours at room temperature (Note 3). 

If the triphenylmethylphosphonium bromide is added too rapidly, the evolution of butane causes excessive frothing of the solution. 

Triphenylmethylphosphonium bromide A pressure bottle is charged with a solution of 55 g (0.21 mole) of triphenylphosphine in 45 ml of dry benzene and cooled in an ice-salt bath. A commercially available ampoule of methyl bromide is cooled below 0° (ice-salt bath), opened, and 28 g (0.29 mole, approx. 16.2 ml) is added to the bottle in one portion. The pressure bottle is tightly stoppered, brought to room temperature, and allowed to stand for 2 days. After this time, the bottle is opened and the product is collected by suction filtration, the transfer being effected with hot benzene as needed. The yield of triphenylphosphonium bromide is about 74 g (99%), mp 232-233°. This material should be thoroughly dried (vacuum oven at 100°) before use in preparing the ylide. 

Triphenylene, 40, 105 Triphenylmethylphosphonium bromide, conversion to methylenetriphen-ylphosphine, 40, ... 

Triphenylmethylphosphonium bromide, preparation for use to prepare Wittig reagent (methylenetri-phenylphosphine), 40, 66... 

Tripheuylmethylphosphoniiun permanganate, (C6Hs) CH,Mn04. Mol. wt. 396.26, violet powder, stable in dark for several weeks, explodes above 70°. The material is prepared (86% yield) by reaction of triphenylmethylphosphonium bromide with K.Mn04 in water.1... 

To a solution of -BuLi (100 mmol) and 200 mL of anhydrous ether is cautiously added triphenylmethylphosphonium bromide 156 (35.7 g, 100 mmol) over 5 min. The reaction was stirred at room temperature for 4 h before adding cyelohexanone 157 (10.8 g, 110 mmol) dropwise. A white precipitate forms and the reaction is heated under reflux overnight. Upon cooling to room temperature, the precipitate is removed by suction and washed with ether. The combined organic phases are washed with water and... 

In 1953 Wittig and Geissler discovered that methylenetriphenyl-phosphorane reacted with benzophenone to give 1,1-diphenylethyl-ene and triphenylphosphine oxide in almost quantitative yield. The phosphorane was prepared from triphenylmethylphosphonium bromide and phenyllithium. 

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