Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-07-25
2004-04-27
Ford, John M. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06727359
ABSTRACT:
Throughout this application, various references are referred to within parenthesis. Disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.
FIELD OF INVENTION
This invention relates to a process for preparing a chemical substance. 6-Methyl-3,4-dihydro-1,2,3-Oxathiazin-4-one dioxide is the compound expressing as the following molecular formula (hereinafter Acesulfame)
Because of the acidic hydrogen on the nitrogen atom, the compound is able to form salts (with bases). The non-toxic salts, for example the sodium, Na, potassium, K and calcium, Ca salt, can, because of their sweet taste, be used as sweeteners in the foodstuffs sector, the K salt (“Acesulfame K”) being of particular importance.
BACKGROUND OF THE INVENTION
Acesulfame-K (AK) is a kind of synthesized high-degree and healthier sweetener. It tastes like cane sugar but 200 times sweeter than the latter. Because of the remarkable characters, such as strong sweet, good stability, fresh taste, fine flavor, no bitter metallic and chemical feeling, cheaper price, safety and no side effect after a large number of toxic tests, AK is a favorite in the international market. Since 1980′s, in many developed countries such as America and Europe, Ak. has widely been used in the production of foods, medicine and cosmetics. These years, with AK more widely being used in beverage and medicine, AK is widely accepted by more and more clients as an important new kind of healthier sweetener.
A number of different processes are known for the preparation of AK and its non-toxic salts. Forty-five patents of Acesulfame filed in five countries were reviewed.
See the following list.
BP
CN
DE
EP
US
Total
4
14
10
3
14
45
The description of the processes for preparing Acesulfame in these patents may be summarized below:
(1) Using fluoro or chlorosulfonyl isocyanate (XSO
2
NCO with x=Cl or F) reacted with tertiary-butylacetoacetate. In the processes, the intermediate fluoro or chlorosulfonyl isocyanate was produced necessarily to use potassium cyanate, that is a very poisonous substance. It is very easy to cause a person working at the post to be seriously hurt, or even death if the safety measures were not perfectly observed. Therefore, this process is not suitable for large industrial production. Additionally, this reaction needs to carry out at lower temperature, thus it is necessary to take much energy that making the productive costs increase. As mentioned above, the process is disuse in industry at present.
(2) Reactions of sulfurylfluoride and acetoacetamide.
(3) Reactions of diketene and sulfamoyl fluoride (H
2
NSO
2
F). In methods (2) and (3) it is difficult to produce sulfurylfluoride and sulfamoyl fluoride in industry. It is necessary to use hydrofluoride for producing the above two substances. A common work lacks perfect safe guard to protect workers against the health hazard of HF. Therefore the above two methods aren't suitable to produce Acesulfame in industry.
(4) The reaction of ring closure of acetoacetamide-N-sulfonic acid with sulfur trioxide at lower temperature was applied to prepare Acesulfame.
But in this process the quantity of sulfur trioxide is as much as four to five times of acetoacetamide-N-sulfonic acid while produced 1 ton of Acesulfame therefore 2 tons of waste sulfuric acid was given here, it was very difficult for manufacturers to treat so large amount of waste acid. The reaction of ring closure must be carried out at lower temperature so it needs to take a lot of energy to reduce the temp of reactants. Additionally, sulfur trioxide is very easy to polymerize turning into various forms of Polymers. At room temperature these polymers are in solid form. Thus the concentration of Sulfur trioxide is difficult to control during the period of practical operation. As a result it leads to the unsteady yield of products desired. Sulfurtrioxide is also a strong oxidant as it absorbed water to turn into sulfuric acid which has strong corrosive action to iron or steel equipments. Judging from this the process isn't a good way for preparing Acesulfame.
In CN patent No.1092066 the synthetic methods of Acesulfame are shown in the following reaction equations:
In the above equation (2) sodium azide was used to react with p-chlorophenoxide sulfonylchloride for preparing p-chlorophenoxide sulfonylazide. After completion of the reaction, solvent was required to distill off, but at this moment attention must be paid to the temperature of distillation. If the distilling temperature exceeded 25° C., it was surely to lead to a terrible explosion. It is a dangerous factor that exists in this synthetic process.
In the above equation (3) p-chlorophenoxide sulfonylazide was reduced to amino-group with sodium tetrahydroborate (NaBH
4
), but this reductive agent sparingly dissolves in tetrahydrofuran. Under this condition the reductive time, was very long that caused the reductive effect bad, therefore it made the yield of the product unsteady according to the above mention in CN patent 1092066. The two defects of the synthetic processes of Acesulfame must be modified to the reaction equations (2) and (3). Therefore, we have done many experiments in order to find a good way to replace the above reaction equations (2) and (3).
This object has been achieved according to the invention by a modification of the process of China patent publication No.1092066.
Our group found an advertisement in a German Journal in which Acesulfame-K was described in 1983. In 1992, our group had synthesized Acesulfame-K. The result led to filing a patent application in China in 1992.
However, the above synthetic method of Acesulfame-K was not satisfactory. Below describes an improved method for Acesulfame-K.
Acesulfame-K's patents:
No.
Country
Patent No.
1
B.P
1326861
2
B.P
1340911
3
B.P
1452099
4
B.P
1456689
1
DE
2453063 A
1
2
DE
3410233 A
1
3
DE
3410439 A
1
4
DE
3410440 A
1
5
DE
3429039 A
1
6
DE
3531357 A
7
DE
3531358 A
1
8
DE
3527070 A
1
9
DE
3531357 A
10
DE
19859663 A
1
1
EP
0217024
2
EP
0218076
3
EP
2327804
1
USP
3689485
2
USP
3689486
3
USP
3917589
4
USP
3926981
5
USP
3926976
6
U.S.P
3993689
7
U.S.P
4052453
8
U.S.P
4563521
9
U.S.P
4607100
10
U.S.P
5103046
11
U.S.P
5011982
12
U.S.P
1326861
13
U.S.P
1452099
14
U.S.P
1456689
1
CN
85104257
2
CN
85104277
3
CN
85106284
4
CN
86105339
5
CN
86105506
6
CN
86105877
7
CN
90108023
8
CN
90107999
9
CN
93102657
10
CN
85104278
11
CN
1092066 A
12
CN
1257865
13
CN
1154965
14
CN
1336363
15
CN
8610550
Some main differences in preparing Acesulfame-K between German, US patents and our invention are:
Synthetic schemes are different:
1 USP, DE:
2 Our Invention:
B, Raw materials used as synthetic components are different between USP, DE patent and Our Invention:
In USP:
These substances must be manufactured by producer. One can't easily obtain them from market. If one needs to produce (b), (c), NaCN, HF, two poisonous substances must be used in producing processes.
In Our invention:
These substances are very easy to be bought from market.
C, The waste substances occurred in our synthetic ways are less than that of US patent in preparing Acesulfame-K.
In our invention:
All solvents can be recovered from each step, and be reused in precedent steps. By product, Potassium Chlorophenoxide can be easily separated from Acesulfame-k and be reused in the first step.
In US Patent:
The waste substances produced in synthetic Acesulfame-k are more than ours. Such as SO
3
+H
2
O→H
2
SO
4
in U.S. Pat. Nos. 5,011,982 and 5,103,046, those amounts are large, and can't be reusable. Because it contained a lot of impurities and its color is dark brown. So it becomes a big problem to process for producers.
SUMMARY OF THE INVENTION
This invention provides a meth
Liu Haiming
Tian Nianshou
BDL Corporation
Chan Albert Wai-Kit
Elkins Mark
Ford John M.
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