Org. Synth. 1967, 47, 14
DOI: 10.15227/orgsyn.047.0014
BIS(1,3-DIPHENYLIMIDAZOLIDINYLIDENE-2)
[Δ2,2'-Bis(1,3-diphenylimidazolidine)]
Submitted by H.-W. Wanzlick
1
Checked by D. J. LaFollette and Ronald Breslow.
1. Procedure
In a 250-ml. round-bottomed flask equipped with a gas-inlet tube and reflux condenser 20 g. (0.094 mole) of N,N'-diphenylethylenediamine (1,2-dianilinoethane) (Note 1) and 100 ml. of purified triethyl orthoformate (Note 2) are heated by an oil bath under nitrogen (Note 3) for 5 hours. The oil bath is maintained between 190° and 200°, and water is allowed to stand in the condenser. The water in the condenser begins to boil slowly, and the alcohol which is produced is allowed to escape (Note 4). The reaction product which crystallizes during the reaction is filtered after cooling and washed with ether. There is obtained 19–20 g. (91–95%) of product, m.p. 285° (dec.) (Note 5).
2. Notes
1.
1,2-Dianilinoethane, containing water of crystallization, is best dried by melting under vacuum.
2.
Commercial material, distilled.
3.
The
nitrogen is dried by passing it through concentrated
sulfuric acid. It must be nearly oxygen-free; otherwise
1,3-diphenylimidazolidinone-2 is formed, and its removal by recrystallization results in a decreased yield.
4.
An air condenser may also be employed.
5.
The melting range depends on the rate of decomposition during heating. The checkers observed that in an evacuated capillary there is darkening from 270° to 290°, and fairly sharp melting at
299–300°. The product is autoxidizable and is best stored under dry
nitrogen. Preparations which have oxidized on standing may be purified by digesting and washing with
methylene chloride.
3. Discussion
This amino olefin was first prepared by thermal elimination of
chloroform from
1,3-diphenyl-2-trichlormethylimidazolidine,
2 and later by the procedure described here.
3,4 It can also be made by treatment of
1,3-diphenylimidazolinium salts with strong bases.
5,64. Merits of the Preparation
The procedure described is the simplest one known. All other methods also employ 1,2-dianilinoethane as starting material. This method, however, converts it directly into the amino olefin in one step.
The preparative value of this compound lies in the surprising fact that
bis(1,3-diphenylimidazolidinylidene-2) behaves in many reactions (
e.g., with aromatic aldehydes,
2,7 and with carbon acids
2,7,8,9) as if it dissociated to form a "nucleophilic carbene." The hydrolytic cleavage of these derived imidazolidine derivatives makes possible the preparation of formyl compounds, so that the amino olefin can be considered as a potential carbonylation reagent. In many reactions it is not necessary to isolate the reagent, as it may be produced
in situ.
10 It should be pointed out, however, that the reaction of the amino olefin with aldehydes and carbon acids does not actually involve prior dissociation to the
carbene, but it is convenient, from a preparative point of view, to describe it in these terms.
6This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Bis(1,3-diphenylimidazolidinylidene-2)
Δ2,2'-Bis(1,3-diphenylimidazolidine)
sulfuric acid (7664-93-9)
ether (60-29-7)
chloroform (67-66-3)
nitrogen (7727-37-9)
triethyl orthoformate (122-51-0)
carbene (2465-56-7)
methylene chloride (75-09-2)
1,2-dianilinoethane,
N,N'-diphenylethylenediamine (150-61-8)
1,3-diphenylimidazolidinone-2
1,3-diphenyl-2-trichlormethylimidazolidine
1,3-diphenylimidazolinium
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