N-Phenylhydroxylamine (11 g., 0.10 mole)2 (Note
1) and
N-phenylmaleimide (17.4 g., 0.10 mole)3 are suspended in
40 ml. of ethanol contained in a
200-ml. Erlenmeyer flask. To the mixture is added immediately (Note
2)
8.98 g. (11.2 ml., 0.124 mole) of freshly distilled n-butyraldehyde. An exothermic reaction ensues, and the mixture spontaneously heats to the boiling point. A clear slightly yellow solution results which, upon cooling, deposits an almost colorless crystalline cake. The mixture is allowed to stand in the ice box for 1 day; it is then filtered through a
Büchner funnel, and the crystals are washed twice with
25-ml. portions of ice-cold ethanol. The yield of air-dried product, m.p.
99–101°, is
31–32 g. (
92–95%). For further purification the crude material is dissolved in
60 ml. of boiling ethanol on the
steam bath, and the resulting solution is allowed to cool slowly to room temperature. If crystallization does not spontaneously begin in 5–10 minutes, it can then be induced by seeding. After being kept for 5 hours in the refrigerator, the solution is filtered and the colorless crystals are washed twice with
20-ml. portions of cold ethanol. The dried product weighs
29–30 g. An additional recrystallization of the air-dried product from
60 ml. of ethanol gives
26–27 g. (
77–80%) of the pure isoxazolidine, m.p.
106.5–107.5°.