Organic compounds -- part of the class 532-570 series – Organic compounds – Nitrogen attached directly or indirectly to the purine ring...
Reexamination Certificate
2000-02-23
2001-02-20
Shah, Mukund J. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitrogen attached directly or indirectly to the purine ring...
C558S138000, C564S014000
Reexamination Certificate
active
06191276
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of phosphoramidates, and more particularly to their preparation from nitrogen bases and diaryl chlorophosphates.
The use of sterically hindered phosphoramidates such as N,N′-bis[di-(2,6-xylenoxy)phosphoryl]piperazine (hereinafter sometimes “XPP”) as flame retardant additives for synthetic resins, especially thermoplastic resins such as polycarbonates, ABS resins and blends thereof, has been discovered to have particular advantages including improved high temperature stability of the resulting blends. Reference is made, for example, to U.S. Pat. No. 5,973,041 and to copending, commonly owned applications Ser. Nos. 09/235,679 and 09/364,915.
XPP and analogous compounds may be conveniently prepared by the reaction of a diaryl chlorophosphate, such as di-(2,6-xylyl) chlorophosphate, with a heterocyclic compound containing two basic N-H groups, such as piperazine. According to the prior art as illustrated by Talley,
J. Chem. Eng. Data,
33, 221-222 (1983), this reaction is conducted in chloroform as solvent, in the presence of triethylamine as an acid acceptor. The triethylamine is employed in stoichiometric amount or in excess, and reacts with the by-product hydrogen chloride to drive the reaction to completion.
The Talley paper describes the preparation of a number of analogous compounds including those derived from such nitrogen compounds as benzylamine, cyclohexylamine, aniline, ethylenediamine and p-phenylenediamine as well as piperazine. Reported yields were as high as 90% for the reaction with aniline, and as low as 61% for the reaction with p-phenylenediamine. Piperazine afforded XPP in a yield of only 68%, one of the lowest reported.
If the use of XPP as a flame retardant additive is to be commercially feasible, it is necessary to improve its yield by a significant amount. Also, it is desirable to minimize the use of the relatively toxic solvent chloroform and stoichiometric amounts of triethylamine on a commercial scale.
It is of interest, therefore, to develop high-yield methods employing relatively harmless materials for the preparation of XPP and analogous compounds.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that a relatively inexpensive basic inorganic compound, calcium oxide, may be employed as an acid acceptor in the preparation of XPP and analogous compounds, provided at least one dipolar aprotic solvent is employed entirely or in part. When so employed, product yield is high and the reaction is rapid.
Accordingly, in one embodiment the invention is a method for preparing a sterically hindered phosphoramidate which comprises contacting a sterically hindered diaryl chlorophosphate with a basic nitrogen compound containing at least two basic N-H groups in the presence of calcium oxide as an acid acceptor and at least one dipolar aprotic solvent.
In another embodiment the invention is a method for preparing a phosphoramidate which comprises contacting a diaryl chlorophosphate with a basic nitrogen compound containing at least two basic N-H groups in the presence of calcium oxide as an acid acceptor and at least one dipolar aprotic solvent, said phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
Within the context of the present invention a sterically hindered phosphoramidate is one in which at least one aryl substituent linked to heteroatom-phosphorus has at least one substituent on the aryl ring ortho to the aryl-heteroatom-phosphorus linkage. The sterically hindered diaryl chlorophosphates employed in the method of this invention include those having the formula
wherein Ar is an aromatic group, each R
1
is independently alkyl, aryl or halo, Q
1
is oxygen of sulfur, Q
2
is oxygen, sulfur, or NR
1
, and n has the value of 1 up to the number of free valency sites on the aromatic ring and at least one R
1
substituent on the aryl ring is ortho to the heteroatom-phosphorus linkage. Preferably, Ar is a phenyl ring and n has the value of 1-5. Preferably, each R
1
is C
1-4
primary or secondary alkyl; most preferably, methyl, and n is 2 with each substituent ortho to the phosphorus linkage. Thus, preferred chlorophosphates are di-(2,4,6-trimethylphenyl) chlorophosphate and di-(2,6-dimethylphenyl) chlorophosphate, also known as di-(2,6-xylyl) chlorophosphate.
Any compound, acyclic or cyclic, containing at least two basic N-H groups may be employed. Suitable compounds include those of the formula
R
2
NH—CH
2
CH
2
—NHR
2
, (II)
wherein each R
2
is a C
1-4
primary or secondary alkyl radical or both R
2
radicals taken together are ethylene. Illustrative acyclic compounds are N,N′-dimethylethylenediamine and N,N′-diethylethylenediamine. Heterocyclic compounds are generally preferred; they are illustrated by piperazine and 1,2,3,4-tetrahydroquinoxaline, both unsubstituted and substituted. Piperazine is most preferred.
In a preferred embodiment, the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C. In particular. the method of the invention may be used to produce a phosphoramidate of the formula III:
wherein each Q
1
is independently oxygen or sulfur; and each of A
1-4
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue. In an especially preferred embodiment of the invention, each Q
1
is oxygen, and each A
1-4
moiety is a 2,6-dimethylphenoxy moiety or a 2,4,6-trimethylphenoxy moiety. These phosphoramidates are piperazine-type phosphoramidates. In the above formula wherein each Q
1
is oxygen, and each A
1-4
moiety is a 2,6-dimethylphenoxy moiety, the glass transition temperature of the phosphoramidate is about 62° C. and the melting point is about 192° C.
In another preferred embodiment, the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula IV:
wherein each Q
1
is independently oxygen or sulfur; and each of A
5-9
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue; and n is from 0 to about 5. In a more preferred embodiment, each Q
1
is oxygen, and each A
5-9
moiety is independently phenoxy, 2,6-dimethylphenoxy, or 2,4,6-trimethylphenoxy, and n is from 0 to about 5.
In another embodiment the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula V:
wherein each Q
1
is independently oxygen or sulfur; and each of A
10-15
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue. In a more preferred embodiment, each Q
1
is oxygen, and each A
10-15
moiety is independently phenoxy, 2,6-dimethylphenoxy, or 2,4,6-trimethylphenoxy. trimethylphenoxy.
In another embodiment the method of the invention may be used to produce a phosphoramidate having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula VI:
wherein each Q
1
is independently oxygen or sulfur; each of A
16-19
is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or
Balasubramanian Venkataraman
Brown S. Bruce
General Electric Company
Johnson Noreen C.
Shah Mukund J.
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