A
1-l., three-necked, round-bottomed flask equipped with an
air stirrer,
dropping funnel, and
low-temperature thermometer is charged with
38.0 g. (0.200 mole) (Note 1) of 1-phenylcyclopentanecarboxylic acid and
150 ml. of acetone. The mixture is stirred, and
22.3 g. (30.6 ml., 0.221 mole) of triethylamine is added over 5 minutes (a 2° rise in temperature is observed). The solution is chilled to −5 to 0° in an
ice-salt bath, and
24.0 g. (21.1 ml., 0.221 mole) of ethyl chlorocarbonate (Note
2) in
50 ml. of acetone is added slowly (25 minutes), maintaining the temperature between −5 to 0°. After the addition is complete, the cold mixture is stirred for an additional 15 minutes. A solution of
26.0 g. (0.400 mole) of sodium azide in 75 ml. of water is added over a 25-minute period while the temperature is kept at −5 to 0°. The mixture is stirred for 30 minutes longer at this temperature, poured into 750 ml. of ice water, and shaken with four
250-ml. portions of toluene (Note
3). The combined
toluene extracts are dried over anhydrous
magnesium sulfate and transferred to a
2-l., three-necked, round-bottomed flask equipped with a
two-necked, Claisen-type adapter, stirrer, and
reflux condenser. The stirred solution is heated cautiously (Note
4) under reflux for 1 hour on a steam bath (
nitrogen evolution is observed initially). The
toluene is then removed at 50° with a
rotary evaporator (aspirator pressure). The flask containing the residual, oily isocyanate is again fitted with the Claisen-type adapter, stirrer, and reflux condenser. The oil is stirred, cooled in an
ice bath, and
300 ml. of 8 N hydrochloric acid (Note
5) is added. The cooling bath is removed, the stirred mixture is gradually heated on a
steam bath (Note
6) until
carbon dioxide evolution has subsided (30 minutes), and the solution is heated under reflux for 10 minutes. The flask is evacuated with a
water aspirator and warmed in a bath at 50° for about 10 minutes. About 10–20 ml. of distillate is collected before a crystalline product separates (Note
7). Ice water (200 ml.) is added to the flask with cooling in an ice bath, and
1 l. of 2.5 N sodium hydroxide is added slowly to pH 12. The mixture is shaken with three
200-ml. portions of diethyl ether, the combined extracts are dried over anhydrous
magnesium sulfate, and the
ether is removed by distillation at 50° with a water aspirator, yielding
29.7 g. of an oil. Distillation of the crude product gives
24.5–26.1 g. (
76–81%) of
1-phenylcyclopentylamine, b.p.
112–114° (9 mm.),
nD20.5 1.5439 (Note
8).