Pimelic acid from benzoyl piperidine

Benzoyl piperidine. In a 1-litre three-necked flask, equipped with a mechanical stirrer, separatory funnel and a thermometer, place 85 g. (99 ml.) of redistilled piperidine (b.p. 105-108°) and a solution of 53 g. of sodium hydroxide in 400 ml. of water. Stir the mixture and introduce during the course of 1 hour 140 g. (115-5 ml.) of redistilled benzoyl chloride maintain the temperature at 35-40°, Cool to room temperature and extract the benzoyl piperidine with ether. Wash the ethereal solution with a little water to remove any dissolved sodium hydroxide, and dry with anhydrous potassium carbonate. Remove the ether on a water bath and distil the residue under diminished pressure (Fig. II, 20, 1). Collect the benzoyl piperidine at 184-186°/15 mm. it is an almost colourless viscous liquid and crystallises on standing in colourless needles m.p. 46°. The yield is 170 g. 

Pimelic acid. Heat a mixture of 18 g. of pentamethylene dicyanide and 250 g. of 50 per cent, sulphuric acid by weight in a 750 ml. round-bottomed flask under reflux for 9 hours. Most of the pimelic acid separates from the cold reaction mixture. Filter off the crystalline acid upon a sintered glass funnel. Saturate the filtrate with ammonium sulphate and extract it with three 50 ml. portions of ether. Dissolve the residue on the filter (which is slightly discoloured, but is fairly pure pimelic acid) in the combined ethereal extracts, dry with anhydrous sodium or magnesium sulphate, and remove the ether by distillation. Recrystallise the residual solid acid from benzene containing 5 per cent, of ether. The yield of pure pimelic acid, m.p. 105-106°, is 22 g. 

Fit a 3-litre round-bottomed flask with a long reflux condenser and a dropping funnel (1). Place a mixture of 400 ml. of concentrated nitric acid and 600 ml. of water in the flask and heat nearly to boiling. Allow 100 g. (116 ml.) of eyeZopentanone (Section 111,73) to enter the hot acid dropwise, taking care that the first few drops are acted upon by tlie acid, otherwise an explosion may occur the addition is complete in 1 hour. Much heat is evolved in the reaction so that the flame beneath the flask must be considerably lowered. Owing to the evolution of nitrous fumes, the reaction should be carried out in the fume cupboard or the fumes 

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