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Org. Synth. 1932, 12, 10
DOI: 10.15227/orgsyn.012.0010
BENZYL PHTHALIMIDE
[Phthalimide, N-benzyl-]
Submitted by Richard H. F. Manske
Checked by Henry Gilman and H. J. Harwood.
1. Procedure
An intimate mixture of 166 g. (1.2 moles) of anhydrous potassium carbonate (Note 1) and 294 g. (2 moles) of phthalimide is treated with 506 g. (4 moles) of benzyl chloride (Note 2), and the mixture is heated in an oil bath at 190° under a reflux condenser for three hours (Note 3). While the mixture is still hot, the excess benzyl chloride is removed by steam distillation (Note 4). Near the end of this operation the benzyl phthalimide crystallizes. It is advisable to cool the mixture rapidly with very vigorous agitation so that the material is in as fine a state of division as possible. The solid is filtered on a large Büchner funnel, thoroughly washed with water, and drained as completely as possible by suction. It is then washed once with 400 cc. of 60 per cent alcohol and drained again. The yield of this product, melting at 100–110°, is 340–375 g. (72–79 per cent of the theoretical amount). It is conveniently purified by crystallizing from glacial acetic acid. The recovery in the crystallization is about 80 per cent, and the pure product melts at 116° (corr.) (Note 5).
2. Notes
1. The potassium carbonate is conveniently dehydrated by heating in a large basin over a moderate flame. It must be ground to a very fine powder and mixed with the phthalimide in a mortar.
2. A good grade of benzyl chloride having a boiling range of 3° was used.
3. There is no apparent advantage in using mechanical stirring.
4. The excess benzyl chloride is recovered from the distillate and dried with calcium chloride. About 200–300 g. is recovered.
5. Using the same general procedure trimethylene bromide furnishes γ-bromopropylphthalimide and, as a by-product, α,γ-diphthalimidopropane, while β-phenylethyl bromide gives β-phenylethylphthalimide.
3. Discussion
Benzyl phthalimide can be prepared from potassium phthalimide and benzyl chloride;1 from phthalimide, potassium carbonate, and benzyl chloride;2 and from phthalimide, sodium ethoxide, and benzyl chloride.3 The two latter procedures avoid the preparation of potassium phthalimide. Phthalic anhydride, benzylamine, and glacial acetic acid on refluxing also furnish benzyl phthalimide.4 The procedure described has been published.2
This preparation is referenced from:

References and Notes
  1. Gabriel, Ber. 20, 2227 (1887).
  2. Ing and Manske, J. Chem. Soc. 1926, 2348.
  3. Weisz and Lányi, Magyar Chem. Folyóirat 39, 153 (1933) [C. A. 28, 5815 (1934)].
  4. Vanags, Acta Univ. Latviensis, Kim. Fakultat. Ser. 4, No. 8, 405 (1939) [C. A. 34, 1983 (1940)].

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

calcium chloride (10043-52-4)

potassium carbonate (584-08-7)

acetic acid (64-19-7)

Trimethylene bromide (109-64-8)

phthalic anhydride (85-44-9)

sodium ethoxide (141-52-6)

benzyl chloride (100-44-7)

Potassium Phthalimide (1074-82-4)

Phthalimide (85-41-6)

BENZYL PHTHALIMIDE

Phthalimide, N-benzyl- (2142-01-0)

γ-bromopropylphthalimide

β-phenylethyl bromide (103-63-9)

β-phenylethylphthalimide

benzylamine (100-46-9)

α,γ-diphthalimidopropane