Preparation of 2-methyl-4-selenoquinazolone
Busch prepared quinazolines by the action of o-amino or o-nitro benzylamine with phosgene, and thioquinazolines with carbon disulphide[(51)]:
Accordingly the same reaction was tried with o-nitrobenzylamine, prepared by the method of Lellmann and Stickel[(50)], using carbon diselenide[(51)]. The reaction seemed to work, but the mixture formed was difficult to extract and it appeared that other reactions took place at the same time, due to the impurity of the carbon diselenide, as the latter has never been prepared in the pure state.
Another method, which is equally attractive because of its simplicity, is that of Gabriel and Stelzner[(52)],
In accordance with the above reaction o-aminobenzaldehyde should work with equal ease with selenocarbamide, but the initial materials were not available.
The reaction which was used successfully was that of Bogert, Breneman and Hand[(53)],
The hydrogen selenide used in the reaction was prepared from FeSe by the action of hydrochloric acid, or by heating paraffin and selenium, in the proportion of four to one respectively, at 335° to 350°C[(54)].
The selenoquinazoline was prepared from anthranilic nitrile by the following methods—the anthranilic nitrile being prepared from o-nitraniline[(57)],
(a) 20 grams of acetyl-anthranilic nitrile was dissolved in absolute alcohol, and dry hydrogen selenide and dry ammonia passed into the solution for three hours. The quinazoline crystallized out gradually on cooling was filtered out and recrystallized from dilute alcohol. The yield was about ten per cent.
(b) 10 grams of acetyl-anthranilic nitrile was heated in a sealed tube at 110° with alcohol saturated at zero degrees with dry hydrogen selenide and dry ammonia. After five hours, the tube was taken out and the quinazoline crystallized out on cooling. Yield was about sixteen per cent.
As hydrogen selenide was somewhat unstable and did not dissolve freely in alcohol, freshly prepared sodium selenide was used in the following method and was found to be more satisfactory. It was prepared from sodium hydroxide in absolute alcohol by passing dry hydrogen selenide into the solution for about three hours. In the beginning and end of the reaction, nitrogen was used to exclude the oxygen of the air. The selenide was collected and dried in an atmosphere of nitrogen, and then in a vacuum, in presence of phosphorus pentoxide. When thus prepared, sodium selenide was colorless, but on exposure to air it turns reddish and finally dark colored. The C. P. selenide on the market was black and was found to be entirely useless.
(c) 20 grams of anthranilic nitrile and fifty grams of sodium selenide were mixed and heated in a distilling flask in an atmosphere of nitrogen, and forty grams of acetic anhydride dropped into the flask very slowly. The temperature was kept at 115° for half an hour and then raised to distill off the acetic acid formed in the reaction, as the condensation hardly went to completion in the presence of any trace of acetic acid. The whole process took an hour and a half. The flask was removed from the oil bath and, after cooling, dilute alkali was run in, in successive portions, to dissolve out the quinazoline. Into the clear alkaline extracts carbon dioxide was bubbled for an hour, and common salt then added. The precipitate was recrystallized several times from twenty-five per cent. alcohol. The yield was from twenty to twenty-five per cent.
(d) 10 grams of anthranilic nitrile, twenty grams of acetic anhydride, and twenty-five grams of sodium selenide were mixed in a sealed tube and heated together for three hours and a half at 110°-115°. The condensation product was crystalline when the tube was cooled to room temperature. The contents of the tube were extracted with dilute alkali as before, filtered, precipitated by carbon dioxide, and recrystallized from dilute alcohol. The yield was not over twenty per cent.
(e) An attempt was made to make o-aminobenzoselenamide, and from the latter, by treatment with acetic anhydride, to form the quinazoline, but the yield of the amide was too small to carry the reaction further.
The substance prepared by the above methods crystallizes from dilute alcohol in needles or prisms of dark brown color. It melts at 213.5° (corr.). It dissolves readily in hot alcohol but on concentration sometimes forms a sticky mass with a peculiar but not unpleasant odor. It dissolves readily in alkalis and is slightly soluble in hot benzene and chloroform, but insoluble in hot water. Crystals purified from (a) were analyzed and gave the following results:
| Calculated for C9H8N2Se | Found | ||
|---|---|---|---|
| I | II | ||
| Carbon | 48.38% | 48.45% | 48.62% |
| Hydrogen | 3.61 | 3.82 | 3.52 |
| Nitrogen | 12.55 | 12.51 | 12.66 |
| Selenium | 35.46 | 35.60 | 35.42 |
The crystals on standing in the presence of air and light decomposed with separation of finely divided selenium and methyl quinazolone.