Process for the preparation of N,N′-carbonyldiazoles...

Details Process for the preparation of N,N′-carbonyldiazoles... Process for the preparation of N,N′-carbonyldiazoles...

2001-07-17

2002-10-15

McKane, Joseph K. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C548S313700, C548S335100, C548S365100

Reexamination Certificate

active

06465658

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to improved processes for the preparation of N,N′-carbonyldiazoles by reaction of azolide salts with phosgene and for the preparation of azolide salts.
It is already basically known that N,N′-carbonyldiazoles can be obtained if azoles are reacted with phosgene (see DE-B 10 33 210, Chem. Ber. 96, 3374 (1963), Org. Synth. Coll. Vol. IV, 201-204 (1968), and EP-A 692,476).
It is disadvantageous in all these processes that half of the azole employed is consumed as scavenger for the hydrogen chloride formed, and therefore only a maximum of 50% of the azole employed can be converted into the desired carbonyidiazole. This is a severe disadvantage, since azoles are expensive products and large azole consumption thus causes high production costs. Furthermore, the azole hydrochlorides are partially obtained in the form of a tacky precipitate, which can be separated off from the carbonyidiazole prepared only with difficulty. Finally, the azole hydrochloride formed as by-product must be disposed of, which causes additional costs.
The process for the synthesis of N,N′-carbonyidiimidazole in accordance with U.S. Pat. No. 4,965,366 attempts to avoid these disadvantages by reacting imidazole with chlorotrimethylsilane in a first reaction step to give trimethylsilylimidazole. An amine (for example, 1,2-diaminoethane) is added at this step in order to scavenge the hydrogen chloride, and the resultant amine hydrochloride is filtered off and either fed to recovery of the amine or disposed of. The trimethylsilylimidazole formed in the reaction furthermore has to be purified by distillation before the further reaction. In the next step, the trimethylsilylimidazole is reacted with phosgene. In this reaction, chlorotrimethylsilane is re-formed, and can, after purification, be reused in the reaction. Disadvantages in this process are the many synthesis and purification steps and the fact that chlorotrimethylsilane is difficult to handle due to its hygroscopic and corrosive properties. In total, three assistants have to be employed for this N,N-carbonyldiimidazole synthesis, namely chlorotrimethylsilane, 1,2-diaminoethane, and sodium hydroxide solution. In addition, the amine, the imidazole, and the solvent required for the trimethylsilylimidazole synthesis have to be dried in a complex procedure.
SUMMARY OF THE INVENTION
A process has now been found for the preparation of N,N′-carbonyl-diazoles of the formula (I)
in which
X
1
, X
2
, and X
3
independently of one another are each CR
1
or nitrogen,
where R
1
is hydrogen or C
1
-C
6
-alkyl, and
R
2
is hydrogen,
or in which
X2 is as defined above, and
X
1
and X
3
are CR
1
, where the R
1
of each X
1
is hydrogen or C
1
-C
6
-alkyl, and the R
1
of each X
3
, together with R
2
of the same diazole ring, forms a —CH═CH—CH═CH— bridge,
comprising reacting azolide salts of the formula (II)
in which
M
⊕
is an equivalent of an alkali metal or alkaline earth metal cation or a quaternary onium ion of the formula (III)
[Y R
3
R
4
R
5
R
6
]
⊕
  (III),
 in which
Y is phosphorus or nitrogen, and
R
3
, R
4
, R
5
, and R
6
independently of one another are each C
1
-C
20
-alkyl, phenyl, benzyl, or ethylbenzyl, and
the other symbols are as defined for the formula (I),
with phosgene in an aromatic compound or an ether as solvent.
DETAILED DESCRIPTION OF THE INVENTION
Preferably in the formulas (I) and (II), X
1
and X
2
, independently of one another, are CH, N, or CCH
3
, X
3
is CH, and R
2
is hydrogen, or X
1
is CH, X
2
is CH, N, or CCH
3
, and X
3
is CR
1
, where R
1
and R
2
together form a —CH═CH—CH═CH— bridge.
In the formula (II), M
⊕
is preferably one mol of lithium, sodium, or potassium cations or ½ mol of magnesium cations or 1 mol of a quaternary onium ion of the formula (III), where Y is phosphorus or nitrogen and R
3
, R
4
, R
5
, and R
6
are C
1
-C
8
-alkyl, or R
3
, R
4
, and R
5
are C
1
-C
6
-alkyl and R
6
is C
4
-C
20
-alkyl, phenyl, benzyl, or ethyl. In particular, M
⊕
is 1 mol of lithium, sodium, or potassium cations.
Particular preference is given to the use of sodium imidazolide or potassium imidazoline or the corresponding 1,2,4-triazolides, pyrazolides, or benzimidazolides, and particular preference is given to the preparation of N,N′-carbonyidiimidazole, N,N′-carbonyldi(1,2,4-triazole), N,N′-carbonyl-dipyrazole, or N,N′-carbonyldibenzimidazole.
In the process according to the invention, from 0.25 to 0.60 mol, for example, of phosgene can be employed per mole of azolide salt of the formula (II). This amount is preferably from 0.45 to 0.55 mol.
Suitable solvents are aromatic compounds, such as benzene, toluene, xylenes, monochlorobenzene, dichlorobenzenes and trichlorobenzenes, and ethers, such as acyclic and cyclic mono- and oligoethers, for example, diethyl ether diisopropyl ether, methyl tert-butyl ether, dibutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxane. It is also possible to employ mixtures of these solvents with one another. Preference is given to 2-methyltetrahydrofuran and aromatic solvents, particularly benzene, toluene, xylenes, monochlorobenzene, dichlorobenzenes, and mixtures of these solvents. The preferred solvents can be dried in a simple manner, for example, by azeotropic distillation. A water content of the solvent of less than 0.1% is preferred.
The process according to the invention can be carried out, for example, at temperatures in the range from 10 to 120° C. Preference is given to temperatures in the range from 20 to 110° C., particularly those in the range from 40 to 100° C. The reaction temperature is preferably selected at least sufficiently high that the N,N′-carbonyldiazole of the formula (I) formed does not precipitate during the reaction.
Azolide salts of the formula (II) are accessible, for example, in accordance with J. Am. Chem. Soc. 102, 4182 or EP-A 352,352. However, these processes are inconvenient and complex since either reagents which are difficult to handle are required (for example sodium hydride or butyllithium) or the azolide salt must be isolated and purified. However, a particularly favorable process for the preparation of azolide salts of the formula (II) has also been found, the details of which are described below. In the process according to the invention for the preparation of N,N′-carbonyldiazoles of the formula (I), azolide salts of the formula (II) that have been prepared by the process according to the invention for the preparation of azolide salts of the formula (II) are preferably employed. This has the advantage, for example, that the azolide salt of the formula (II) does not have to be isolated but instead can be employed in the form of the reaction mixture obtained in its preparation according to the invention, if desired after removal of the solvent of the formula (VII) by distillation.
It is advantageous to carry out the process according to the invention for the preparation of N,N′-carbonyldiazoles in the presence of a phase-transfer catalyst. Suitable phase-transfer catalysts are, for example, those of the formulas (VIII) to (X):
in which
R
3
, R
4
, R
5
, and R
6
are as defined for the formula (III),
R
10
in each case independently of the others is C
1
-C
20
-alkyl, phenyl, benzyl, or ethylbenzyl,
R
11
independently of R
10
is as defined for R
10
, or
R
10
and R
11
together form a (—CH
2
—)
n
bridge, where n is an integer from 1 to 10,
R
12
is NR
10
R
11
, C
1
-C
20
-alkyl, phenyl, benzyl, orethylbenzyl, and
Z
−
is Cl
−
, Br
−
, I
−
, OH
−
, HSO
4
−
, BF
4
−
, or PF
6
−
.
Azoles of the formula (IV) (see below) can also be employed as phase-transfer catalysts.
Based on one mole of azolide salt of the formula (II), it is possible to include, for example, from 0.0001 to 0.2 mol, preferably from 0.00

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