Org. Synth. 1955, 35, 65
DOI: 10.15227/orgsyn.035.0065
ETHYL N-PHENYLFORMIMIDATE
[Formimidic acid, N-phenyl-, ethyl ester]
Submitted by Royston M. Roberts and Paul J. Vogt
1.
Checked by T. L. Cairns and J. J. Drysdale.
1. Procedure
A 500-ml. flask is equipped with a capillary through a side opening, and 94 g. (1.01 moles) of aniline and 1 ml. of concentrated hydrochloric acid are added. A 12-in. glass-helix-packed column is attached (Note 1), and the water introduced with the acid is removed by boiling; about 1 ml. of aniline is collected after the water has distilled. The flask and its contents are then cooled to room temperature, and 222 g. (1.50 moles) of ethyl orthoformate is added. The column is reattached, and ethanol (Note 2) is distilled as it is produced; the theoretical amount (92 g., 116 ml.) is obtained in about 2.25 hours.
The reaction mixture is allowed to cool slightly, and the pressure is lowered to 40 mm. (Note 3). The excess ethyl orthoformate is distilled at 65°/40 mm. After a small intermediate fraction of about 4 g., b.p. 65–117°/40mm., the product distils at 117–118°/40mm. (b.p. 87–88°/10mm.; nD25 1.5248); the yield is 118–127 g. (78–84%). The residue amounts to about 14 g. and is mainly N,N'-diphenylformamidine (Note 4).
2. Notes
1.
A
Vigreux column may also be used since it is not difficult to separate the
ethanol from
ethyl orthoformate, the next most volatile component present. A total reflux, partial take-off head was used. Heat was supplied by an
electric mantle; the column was heated with a glass-covered heating tape during the distillation of excess
ethyl orthoformate and product.
2.
A small amount (5–10 ml.) of lower-boiling material usually comes over before the
ethanol; this is probably
ethyl formate, produced by hydrolysis of the
ethyl orthoformate.
3.
A
pressure regulator may conveniently be used in conjunction with a
water aspirator.
4.
If several runs are to be made, the residue may be saved and used as starting material, since the reaction proceeds via the initial formation of
N,N'-diphenylformamidine and its subsequent reaction with
ethyl orthoformate.
2,3.
3. Discussion
Ethyl N-phenylformimidate has been prepared from
silver formanilide and
ethyl iodide,
4 and from
aniline and
ethyl orthoformate.
3 This method incorporates the discovery
2 of the necessity of acid catalysis for satisfactory yields by the latter process.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ethanol (64-17-5)
hydrochloric acid (7647-01-0)
aniline (62-53-3)
Ethyl orthoformate
ethyl formate (109-94-4)
N,N'-diphenylformamidine
Ethyl iodide (75-03-6)
Ethyl N-phenylformimidate,
Formimidic acid, N-phenyl-, ethyl ester (6780-49-0)
silver formanilide
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