Process for preparing a sulfinate

Details Process for preparing a sulfinate Process for preparing a sulfinate

2001-06-26

2002-06-04

Vollano, Jean F. (Department: 1621)

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

Organic compounds

Sulfinic or sulfenic acids or salts thereof

Reexamination Certificate

active

06399815

ABSTRACT:

FIELD OF THE INVENTION
This invention is related to a process for preparing a sulfinate which is useful for a synthetic intermediate of an organic compound.
BACKGROUND OF THE INVENTION
It is common practice that sulfones be synthesized by oxidation of sulfides or sulfoxides, by alkylation of salts of sulfinic acids, by a Friedel-Crafts reaction between aromatic compounds and sulfonyl halides, by dehydrated condensation of aromatic compounds with sulfonic acids, by a reaction of Grignard reagents and esters of sulfonic acids, or by an addition of sulfonyl halides or sulfinic acids to unsaturated compounds. Of these reactions, oxidation of sulfides or sulfoxides and alkylation of salts of sulfinic acids are frequently used because they produce sulfones at a high yield. Said oxidation of sulfides or sulfoxides gives results in a high reaction yield. But unfortunately, multi-step reactions are needed to synthesize said sulfides or said sulfoxides used as raw materials and, at the same time, said sulfides or sulfoxides give off a strongly unpleasant odor. In effect, the use of this reaction has several drawbacks in respect to environmental aspect, handling aspect, and cost. In contrast to this reaction, said alkylation of salts of sulfinic acids is superior to the other preparation methods from an industrial point of view, because said salts of sulfinic acids can be synthesized with comparative ease and they have no unpleasant odor.
It is also common practice that sulfinic acids or their salts be synthesized by reduction of sulfonyl chlorides and by a reaction of sulfur dioxide with Grignard reagents or diazonium salts. Of these reactions, reduction of sulfonyl chlorides is most widely used. The reducing reagents for sulfonyl chlorides can be selected from: Zn(F. C. Whitmore, et al., Org. Synth., I, 492 (1941)); sodium sulfite(S. Smiles, et al, Org. Synth., I, 7 (1941)); sodium hydrogensulfite(R. Mercanton, et al., Helv. Chim. Acta., 28, 538 (1945)); or sodium sulfide(E. Fromm, et al., Ber., 42, 3821 (1909)). Of these reagents, sodium sulfite or sodium hydrogensulfite are often used and reaction yields are quite satisfactory.
It is well known that free sulfinic acids are unstable, and also that they disproportionate in solid or in solution to produce thiosulfonates and sulfonic acids. On the other hand, salts of sulfinic acids are so stable that they are suitable to be handled in the industrial settings. Neutralization of sulfinic acids obtained by the reduction of the above-mentioned sulfonyl chlorides with inorganic bases is commonly used to synthesize sulfinic acids. As for inorganic bases, sodium hydroxide and sodium hydrogencarbonate are often used. However, when sodium hydroxide is used, sulfonic acids are formed as by-products due to its strong alkalinity. And, when sodium hydrogensulfite is used, carbon dioxide is vigorously produced during neutralization and is quite hazardous. This invention is expected to further improve the process to overcome these synthetic problems in the industry.
Photographic couplers are commonly used in silver halide color photosensitive materials. Said couplers having a sulfonyl group are widely used, such as in unexamined and published Japanese Patent Application Nos. 10-97039 and 2000-19697. Couplers having sulfonyl groups show good color forming reactivity, good color reproduction quality, and good image stability, all of which are important photographic properties, and they are thus suitable for photographic color couplers.
One of the common methods to introduce sulfonyl groups into photographic couplers is to react acid chlorides containing sulfonyl groups with coupler residues containing amino groups in the presence of base catalysts. But, the reaction selectivity of acid chlorides towards amino groups is small due to a high reactivity of acid chlorides, and this will cause a decrease in yield as well as in purity of the product. At the same time, acid chlorides must be handled with extreme care because they are highly corrosive.
SUMMARY THE INVENTION
This invention is presented to solve the above problems. The object of the present invention is to provide a process for preparing a sulfinate which is useful for a synthetic intermediate of an organic compound as well as for a photographic coupler of high yield, high purity, and with ease of production. Another object of this invention is to provide a process for preparing a photographic coupler by the use thereof, again of high yield and ease of production.
The object of the present invention can be achieved by the following processes.
(1) A process for preparing a sulfinate through reduction of a sulfonyl chloride with a sulfite or a hydrogensulfite, in the presence of a hydrogenphosphate.
(2) The process of the above-mentioned process (1) wherein the reduction is accomplished in a mixture of at least one organic solvent and water.
(3) The process of the above-mentioned process (1) wherein the sulfinate is represented by Formula (I),
R
1
SO
2
M  Formula (I)
wherein R
1
is an aryl group ; M is a sodium atom or a potassium atom.
(4) The process of the above-mentioned process (1) wherein said sulfonyl chloride is represented by Formula (II),
R
1
SO
2
Cl  Formula (II)
wherein R
1
is an aryl group.
(5) The process of the above-mentioned process (3) wherein said sodium sulfinate and said potassium sulfinate represented by Formula (I) is one selected from the group consisting of I-1 to I-15.
(6) The process of the above-mentioned process (4) wherein said sulfonyl chloride represented by Formula (II) is one selected from the group consisting of II-1 to II-14.
(7) The process of the above-mentioned process (2) wherein the organic solvent is one selected from the group consisting of methanol, ethanol, isopropanol, butanol, tert-butanol, acetonitrile, ethyl acetate, toluene, dichloromethane, tetrahydrofuran, acetone, and N, N-dimethylformamide.
(8) The process of the above-mentioned process (7) wherein the organic solvent is one selected from the group consisting of ethanol, isopropanol, tert-butanol, and acetonitrile.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is detailed below. The sulfinate, the sulfite, the hydrogensulfite, and the hydrogenphosphate of the present invention comprise a cation of a metal or an ammonium in their molecular structure. Preferably, said cation of a metal or an ammonium is one selected from the group consisting of Na
+
, K
+
, Li
+
, Mg
++
, Ca
++
, NH
4
+
. And more preferably said cation of a metal is Na
+
or k
+
.
Disodium hydrogenphosphate, used in the present invention, is also known as sodium secondary phosphate, disodium phosphate, or sodium dibasic phosphate. It exists in the form of an anhydrous state or with water of crystallization. Dipotassium hydrogenphosphate is also known as potassium secondary phosphate or dipotassium phosphate.
Disodium hydrogenphosphate and dipotassium hydrogenphosphate used in the present invention may be prepared by neutralizing phosphoric acid with either sodium hydroxide, sodium carbonate, potassium hydroxide, or potassium carbonate and further may be used in a buffer solution of pH 9-10.
The sodium sulfinate or potassium sulfinate prepared in the present invention can contain water of crystallization. In case when free sulfinic acids are stable, one can neutralize the sodium sulfnates or potassium sulfinates with mineral acids to isolate the free sulfinic acids.
Sodium sulfite used in the present invention is also known as soda sulfite, and both an anhydrous salt and a water-of-crystallization containing salt are known. Sodium hydrogensulfite is also known as sodium bisulfite or sodium acid sulfite. Sodium sulfite is commercially available in a mixture of sodium hydrogensulfite and sodium pyrosulfite and can be used in the present invention. Potassium sulfite is also known as potassium kali and it is commercially available in a mixture of potassium hydrogensulfite and potassium pyrosulfite and can also be used in the present invention.
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