Checked by G. D. Abrams, Hermann Ertl, and Peter Yates.
1. Procedure
Caution!
Benzenediazonium-2-carboxylate when dry detonates violently on being scraped or heated, and it is strongly recommended that it be kept wet with solvent at all times. It should be prepared and used in a
hood behind a safety screen. A wet towel or sponge should be kept within easy reach with which to deactivate any spilled material, which should then be disposed of by flooding with water.
A.
Benzenediazonium-2-carboxylate. A solution of
34.2 g. (0.25 mole) of anthranilic acid (Note
1) and
0.3 g. of trichloroacetic acid (Note
2) in
250 ml. of tetrahydrofuran (Note
3) is prepared in a
600-ml. beaker equipped with a
thermometer and cooled in an
ice-water bath. The solution is stirred magnetically, and
55 ml. (48 g., 0.41 mole) of isoamyl nitrite (Note
4) is added over a period of 1–2 minutes. A mildly exothermic reaction occurs, and the reaction mixture is maintained at 18–25° and stirred for a further 1–1.5 hours. A transient orange to brick-red precipitate may appear (Note
5) which is slowly converted to the tan product. When the reaction is completed, the mixture is cooled to 10°, and the product is collected by suction filtration on a
plastic Buchner funnel and washed on the funnel with cold
tetrahydrofuran until the washings are colorless.
(Caution! The filter cake should not be allowed to become dry.) The
benzene-diazonium-2-carboxylate is then washed with two
50-ml. portions of 1,2-dichloroethane to displace the
tetrahydrofuran, and the solvent-wet material is used in the next step (Note
6), (Note
7), and (Note
8).
B.
Biphenylene. The solvent-wet
benzenediazonium-2-carboxylate is washed from the funnel into a
400-ml. beaker with
ca. 150 ml. of 1,2-dichloroethane, dispensed from a
plastic wash bottle, with the aid of a
plastic spatula (Note
9). The resultant slurry is added during 3–5 minutes to
1250 ml. of gently boiling, stirred 1,2-dichloroethane in a
2-l. beaker on a
magnetic stirrer-hot plate in the hood (Note
10). Frothing ceases a few minutes after completion of the addition, and the mixture assumes a clear red-brown color, signaling the end of the reaction.
A
1-l., two-necked, round-bottomed flask is equipped with a
1-l. addition funnel and a
Claisen distillation head and water-cooled condenser. The cooled reaction mixture is transferred to the funnel, and enough of it is admitted to the flask to half-fill the latter. The
1,2-dichloroethane, b.p.
83–84°, is distilled with the use of magnetic stirring to maintain even ebullition; the remainder of the reaction mixture is added from the funnel at a rate such that the flask remains about half-full. When
ca. 75 ml. of dark residue remains in the flask,
300 ml. of ethylene glycol is added. An
air condenser is substituted for the water-cooled condenser, and distillation is recommenced. A forerun, b.p. <150°, is discarded, and the fraction, b.p.
150–197°, is collected (Note
11). The distillate is cooled to 10°, and the product is collected by suction filtration, washed with
10–15 ml. of cold ethylene glycol and several times with water, and dried at atmospheric, pressure over
phosphorus pentoxide. The yield of
biphenylene, m.p.
109–112°, is
4.0–5.6 g. (
21–30%, based on
anthranilic acid). Additional
biphenylene (
0.2–0.5 g.) can be obtained from the mother liquor and
ethylene glycol washings by redistillation or dilution with water (Note
12).
2. Notes
1. The submitters used
practical grade anthranilic acid from Mallinckrodt Chemical Works.
3. The submitters used commercial
tetrahydrofuran. The checkers found that the product yield was the same when either
practical grade or Fisher Certified reagent grade tetrahydrofuran was used.
4. The submitters used
"amyl nitrite" U.S.P. from Mallinckrodt Chemical Works;
isoamyl nitrite supplied by Matheson, Coleman and Bell is apparently the same material. They found that other alkyl nitrites (ethyl,
n-butyl,
t-butyl,
n-amyl) may be used with equal success. Subsequent to the checking of this procedure, they reported that the amount of nitrite can be reduced to a 20% molar excess.
6. The product should be used immediately because it deteriorates slowly at room temperature. It is freed of
tetrahydrofuran by washing with the solvent to be used in subsequent reactions and transferred as a slurry in that solvent (cf.
p.htmrocedure B). Traces of water, if present, do not appear to interfere with subsequent reactions of diazonium carboxylates, as observed in the submitters' laboratory.
7. The submitters have found that this procedure works equally well with many substituted anthranilic acids; however, it does not work with 3-chloro-, 5-cholro, 4-nitro-, 5-nitro-, and 4,5-benzoanthranilic acids.
8. Although it strongly recommended that the product not be dried, particularly when prepared on the scale described here, the following slightly modified procedure can be used for the preparation of solvent-free
benzenediazonium-2-carboxylate. A solution of
2.74 g. (0.020 mole) of anthranilic acid and
0.030 g. of trichloroacetic acid in 30 ml. of tetrahydrofuran is prepared in a
100-ml. beaker equipped with a thermometer and cooled in a bath of
ca. 25 g. of crushed ice. The solution is stirred magnetically, and
5 ml. (4.4 g., 0.038 mole) of isoamyl nitrite (Note
4) is added during
ca. 0.5 minute. The mixture is stirred and allowed to warm to room temperature over a period of 1 hour. It is cooled to 10°, and the product is collected by suction filtration with the use of a plastic Buchner funnel and plastic spatula and washed with ice-cold
tetrahydrofuran until the washings are colorless. The yield of air-dried (30 minutes)
benzenediazonium-2-carboxylate is
2.55–2.88 g. (
86–97%).
(Caution! Danger of detonation! See above.) (Note
13).
10. The checkers added the slurry via a
large, medium-bore, glass funnel with fire-polished edges. In one of three runs a small, sharp report was heard, apparently from a source above the liquid in the beaker; the yield of
biphenylene in this run did not differ significantly from that obtained in the other runs.
11. The checkers found it necessary to heat the condenser with a
microburner from time to time to prevent clogging with
biphenylene. The submitters have reported that this can be avoided by connecting the Claisen head via an
adapter to a
two-necked receiving flask fitted with an
upright water-cooled condenser and cooled by immersion in ice-water.
12. For convenient preparation and workup of larger amounts of
biphenylene, several runs can be combined after the decomposition of the
benzenediazonium-2-carboxylate. Thus the submitters obtained
19.1 g. (
25%) of air-dried
biphenylene by combining four batches. They found that the use of larger amounts of
1,2-dichloroethane resulted in a moderate increase in yield; by combining four batches, each prepared in 2.
75 l. of 1,2-dichloroethane in a
4-l. beaker, they obtained
22.8 g. (
30%) of product.
13. The checkers transferred the solvent-moist product to a
tared Petri dish by means of gentle puff of compressed air through the stem of the funnel; solid adhering to the filter paper and funnel was transferred to the dish with the aid of a
soft rubber policeman, which was also used to spread the product over the surface of the dish. The product was then air-dried for 30 minutes in the hood.
3. Discussion
4. Merits of the Preparation
These procedures illustrate facile methods for the preparation of
benzenediazonium-2-carboxylate and its derivatives
15 and of
biphenylene and certain biphenylene derivatives.
13 The latter preparation is far more convenient and proceeds in much better yield than do previous, syntheses, which involve more steps, less accessible intermediates, and more complicated techniques.
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
Perfluorobutyric or trifluoroacetic acid
2,2'-biphenyliodonium iodide
o,o'-biphenylenemercury
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
magnesium (7439-95-4)
silver oxide (20667-12-3)
1,2-dichloroethane (107-06-2)
cuprous oxide
ethylene glycol (107-21-1)
cupric chloride (7758-89-6)
amyl nitrite (463-04-7)
Anthranilic Acid (118-92-3)
lithium (7439-93-2)
Isoamyl nitrite (110-46-3)
trichloroacetic acid (76-03-9)
Tetrahydrofuran (109-99-9)
phthaloyl peroxide
Benzenediazonium-2-carboxylate,
benzene-diazonium-2-carboxylate (1608-42-0)
Biphenylene (259-79-0)
dibenzomercurole
diphenyliodonium-2-carboxylate (1488-42-2)
1,2,3-benzothia-diazole-1,1-dioxide (37150-27-9)
1-aminobenzotriazole (1614-12-6)
o-fluoro-bromobenzene (1072-85-1)
phosphorus pentoxide (1314-56-3)
Benzenediazonium, o-carboxy-, hydroxide
o-bromoiodobenzene (583-55-1)
lead tetraacetate
2,2'-dicarboxydiazoaminobenzene
2,2'-dibromobiphenyl
2,2'-biphenyl-dimagnesium dibromide
2,2'-diiodobiphenyl
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