Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic halides
Reexamination Certificate
2000-03-14
2002-06-04
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic halides
Reexamination Certificate
active
06399822
ABSTRACT:
Phosgene is used in industrial scale as an important starting compound for the production of diisocyanates and polycarbonates among others. A need for phosgene substitutes has arisen as a result of its high toxicity on the one hand and the highly restrictive legislative safety regulations brought about by this with regard to transport, storage and use on the other hand. This need is covered by diphosgene (trichloromethyl chloroformate) that is liquid at standard conditions and crystalline triphosgene (bis(trichloromethyl)carbonate) [H. Eckert, B. Forster, Angew. Chem., 99 (1987) 922-23; Angew. Chem. Int. Ed. Engl., 26 (1987) 894-95; F. Bracher, T. Litz, J. Prakt. Chem., 337 (1995) 516-18; L. Cotarca, P. Delogu, A. Nardelli, V. Sunjic, Synthesis, (1996) 553-76].
In practice, it has been determined that, as was previously the case, it is advantageous to use gaseous phosgene in chemical production processes. Reasons for this are, for one, that known methods can be run with existing plants and, for another, the fact that work is frequently done with an excess of phosgene that has to be removed after the reaction. However, the separation of excess phosgene mentioned in the latter case often turns out to be difficult with less volatile phosgene substitutes, whereas gaseous phosgene can be easily removed [J. S. Nowick et al., J. Org. Chem., 61 (1996) 3929]. However, as a result of the above mentioned legislative safety regulations, phosgene itself is no longer commercially available. Hence, a need exists for a harmless method of production of pure phosgene,
immediately before its use in the reaction, from stable precursors such as the substitutes diphosgene and
especially triphosgene via their regulated and controllable reaction to phosgene.
Such a reaction of diphosgene and triphosgene on reaction catalysts is already known, but serious disadvantages exist with the known reaction catalysts: thus, triphosgene is stochiometrically reacted on metal salts with strong Lewis acid characteristics, such as aluminum chloride or iron chloride, to phosgene, carbon dioxide and carbon tetrachloride according to the following equation [L. Cotarca, Synthesis, (1996) 556]:
Cl
3
C—O—CO—O—CCl
3
→COCl
2
+CO
2
+CCl
4
.
In this case, the yield of phosgene is only a third of the theoretically possible value therewith. Moreover, the resulting side-products can be disturbing in the subsequent reactions of phosgene and the conversion reaction runs uncontrollably to a great extent. On the other hand, triphosgene is completely stable against weaker Lewis acids such as titanocene dichloride and zirconocene dichloride.
Triphosgene can also be reacted to phosgene on activated charcoal. Although the reaction here is nearly quantitative, the reaction is uncontrollable and can even take on an explosive-like character.
Diphosgene and triphosgene can also be reacted to phosgene on Lewis bases such as pyridine, but in this case, the extremely fast conversion reaction is also not controllable.
In light of this background with the above mentioned disadvantages of the known methods for reacting diphosgene and triphosgene to phosgene, the problem of the present invention is to provide a method for the controllable and substantially quantitative production of phosgene from diphosgene and/or triphosgene.
It was surprisingly found that this problem can be solved by reacting diphosgene and/or triphosgene to phosgene on a catalyst comprising one or more compounds with one or more nitrogen atoms with deactivated free electron pair. Triphosgene can be used in the form mentioned above (bis(trichloromethyl)carbonate) as well as in the cyclic form given in the following formula:
In a preferred embodiment, the deactivation of the free electron pair of the nitrogen atom occurs by mesomerism and/or one or more electron-attracting and/or space-filling groups in the vicinity to the nitrogen atom. The term “in the vicinity” means particularly “in the &agr;-, &bgr;-, or &ggr;-position” to the nitrogen atom with deactivated free electron pair, particularly preferred is “in the &agr;-position”.
Preferred examples of compounds with nitrogen atom with deactivated free electron pair are compounds with deactivated imine and/or deactivated amine function.
In a preferred embodiment, they are immobilized by binding to polymers such as polyacrylic acid or polystyrene. The immobilized compounds with deactivated imine and/or amine function are optionally bound to the polymer chain over spacer molecules (so-called “spacer”. Examples for such spacers are alkoxy groups such as triethylene glycol, tetraethylene glycol and polyethylene glycol groups.
Compounds with deactivated imine function are, for example, higher aromatic or heteroaromatic systems as well as compounds with alkyl groups in the vicinity to the nitrogen atom. Preferred compounds with deactivated imine function that can be used in the method according to the invention are poly-(2-vinylpyridine), phenanthridine as well as phthalocyanine (H
2
Pc) and metal phthalocyanines (MePc) whose skeletal structure is depicted below:
The auxiliary group metals of the 4th to 6th period as well as the metals of the 3
rd
to 6
th
period of the main groups 2 to 5 are preferred as metal atoms of the metal phthalocyanine, and particularly, the auxiliary group metals of the 4
th
period (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn).
The metal atoms of the metal phthalocyanine, especially in the case of the auxiliary group metals, can be complexed with one or more additional ligands such as chloro or oxo. The phthalocyanine and/or the metal phthalocyanines can be used in any crystal modifications. Examples for such crystal modifications of metal phthalocyanines are &agr;-CuPc and &bgr;-CuPc.
The above-mentioned preferred compounds with deactivated imine function can optionally be substituted on the carbon skeleton. The substituents include alkyl, cycloalkyl, aryl, halogen, nitro, amino, cyano, carboxy, carbalkoxy, carboxamido as well as heterocyclic groups.
In a preferred embodiment, the phthalocyanine or the metal phthalocyanines can be substituted once or several-fold independently of each other on the benzo groups, wherein the substituents are preferably selected from the above mentioned substituents as well as further phthalocyanines and condensed cyclic or heterocyclic compounds that are themselves optionally substituted.
The compounds with deactivated amine function are preferably selected from deactivated tertiary amine compounds. The deactivation occurs, in a preferred manner, by immobilization by binding the amine compound to polymers, wherein tertiary alkylamines are particularly preferred, and the alkyl groups are the same or different and are selected from methyl, ethyl, propyl and higher linear or branched alkyl groups. An example for a catalyst with deactivated tertiary amine function according to the invention is N,N-dimethylaminomethyl polystyrene.
The catalyst for reacting diphosgene and/or triphosgene is preferably used at a concentration from 0.01 to 10 mol %, particularly preferred is from 0.1 to 2 mol %, with respect to the amount of diphosgene and/or triphosgene. If the catalyst is a catalyst immobilized to a polymer by binding of a compound with nitrogen atom with deactivated free electron pair, then the concentration is calculated based on the amount of substance (in mol) of the compounds with deactivated free electron pair bound to the polymer chain.
In a preferred embodiment of the method, this is carried out with diphosgene and/or triphosgene in the liquid state. The reaction temperature is preferably 80 to 150° C., more preferably 90 to 130° C. and most preferably 100 to 125° C.
Although the method according to the invention can be carried out without solvent, it is also possible to use an inert solvent in the reaction of diphosgene and/or triphosgene.
The present invention also provides a device for the production of phosgene from diphosgene and/or triphosgene as reaction material that comprises a storage vessel for diphosgene and/or tripho
Dirsch Norbert
Eckert Heiner
Gruber Bernhard
Dr. Eckert GmbH
Forohar Farhad
Geist Gary
Meyer Jerald L.
Nath Gary M.
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