Ethylene Glycol → 4-Amino-4-phenylcyclohexan-1-one

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Reaction Steps

A reaction mixture consisting of 21.9 gm. (0.085 mole) 4-isocyanato-4-phenylcyclohexanone ethylene ketal (prepared as in Example 17, Part G), 10.9 gm. sodium hydroxide, and 210 ml. ethylene glycol is heated at the reflux temperature for sixty-six (66) hours. A solution results which is cooled in an ice-water bath. A small amount of ice is added to the solution followed by 23 ml. of concentrated hydrochloric acid which is added dropwise with stirring. After five minutes, the acidified solution is made strongly basic by adding 50% aqueous sodium hydroxide. The basic solution is diluted with 800 ml. water. The strongly basic, dilute aqueous solution is then extracted four times with 200 ml. portions of diethyl ether. The extracts are combined and washed with water and with brine, before removing the ether by evaporation under reduced pressure. The residue thus obtained is dissolved in 50 ml. of diethyl ether and the oily solution is treated with an equivalent of 3 N hydrogen chloride in diethyl ether. A precipitate forms which is collected on a filter and recrystallized from a mixture of methylene chloride and ethyl acetate. There is thus obtained 15.2 gm. (52% yield) of 4-amino-4-phenylcyclohexanone, ethylene ketal hydrochloride which has a melting point at 226° to 228° C. (with decomposition). A second crop of crystals weighs 1.60 gm. and has a melting range from 222° to 226° C. An analytical sample has a melting point at 248° to 249° C.

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