Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-12-03
2003-09-02
Gerstl, Robert (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
Reexamination Certificate
active
06613943
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to 4-acylamino-2-hydroxy-5-substituted-acylanilide compounds and a method of using them as common intermediates for the preparation of phenolic cyan couplers for color photography.
BACKGROUND OF THE INVENTION
Widely used cyan-dye forming couplers in color photography are 4-substituted-2,5-diaminophenol derivatives. Most of these couplers have been made from 4-halo-2-aminophenols as basic raw materials. Both amino and phenol groups are so reactive and sensitive that blocking both functional groups are required prior to introduction or manipulation of other substituents in the molecule. Formation of oxazole ring is the most commonly used for the blocking purpose. After the blocking, a nitro group is introduced at 6-position of benzoxazole (or 5-position of aminophenol ring) and 5-halo group of benzoxazole (or 4-halo group of aminophenol) is replaced, if necessary, with other groups by nucleophilic replacement reaction. The benzoxazole ring is then opened by hydrolysis, and a photographically useful group is placed on unblocked amine. Reduction of 5-nitro group gives 5-amino-2,4-disubstituted-phenol. Such an aminophenol is difficult to handle because of its reactivity and sensitivity and it is necessary to use it without isolation in the final step. The final step is usually a reaction between 5-amino group and a photographically useful ballasting acyl halide. Such a synthetic route using benzoxazole intermediates has been common and traditional in the synthesis of phenolic cyan couplers and well documented in the literature. Examples are U.S. Pat. No. 4,579,813; U.S. Pat. No. 4,743,595; JP60-091355; and M. Ono, et al, Heterocycles (1988), 27(4), 881-4.
Since 2-amino-4-chloro-5-nitrophenol has been commercially available in a bulk quantity, it has been used exclusively as a raw material in making 2-equivalent phenolic cyan couplers having a coupling-off group other than the halogen at 4-position. The phenolic OH group in the raw material is usually blocked by O-benzylation prior to replacement of 4-chlorine with other coupling-off group. A photographically useful functional group, typically a urea, is formed on unblocked amine. Reduction of 5-nitro group accomplishes deblocking at the same time to generate 5-amino-2,4-disubstituted-phenol. It is usually not isolated and used in the final ballasting reaction. This synthetic sequence starting from 2-amino-4-chloro-5-nitrophenol has been widely used in the preparation of 2-equivalent phenolic cyan couplers. Examples are U.S. Pat. Nos. 4,775,616; 4,849,328; 4,923,791; 5,045,442; and 5,962,198.
A common feature of these two known synthetic routes is to form ‘Urea First and Ballast Amide Last’. There are many significant disadvantages, however, in the preparation of 2-eq phenolic cyan couplers in that manner.
(1) Benzene ring of benzoxazoles is not activated for nitration so that a harsh reaction condition should be employed. For example, a large amount of concentrated sulfuric acid and a pre-formed nitronium ion mixture are usually used. Use of such a large amount of concentrated acid as a reaction medium make it difficult to handle during the reaction and to treat waste after the reaction. This is a disadvantage in safety, yield, and cost
(2) Hydrolysis of oxazole ring is difficult. A polar solvent such as N,N-dimethyl formamide, N,N-dimethyl actamide, N-methyl pyrolidone, and dimethyl sulfoxide and a high temperature of over 100° C. are often required. Use of such a polar solvent is costly and environmentally unfavorable. Such a high temperature required for hydrolysis of benzoxazole containing a nitro group may impose a safety concern. This is a disadvantage in environment, safety, yield and cost.
(3) 2-Amino-4-halo-5-nitrophenol is thermally unstable as most of the low molecular weight aromatic nitro compounds are. Safety is a big issue in using such a thermally unstable compound. There are lots of limits for material usage and in reaction condition. This is a disadvantage in safety, yield, and cost.
(4) When 2-amino4-chloro-5-nitrophenol is blocked by 0-benzylation, 2-amino group is also benzylated although it is in some small extent. Presence of a small amount of impurity has a big impact on isolation and reduces the yield of product substantially. This is a disadvantage in yield and cost.
(5) Reaction of putting something on the amine at 2-position is difficult because of deactivation effect of the nitro group present at para position. It is usually required to employ either an activated reagent such as a carbamoyl chloride or an isocyanate, or a harsh condition such as a high boiling solvent and a high reaction temperature. Use of such an activated reagent may be costly and environmentally unfavorable. Necessity of employing such a harsh condition for a small molecule containing a nitro group may impose a safety concern. This is another disadvantage in environment, safety, yield and cost.
(6) Something put on the amine may cause other difficulties in the subsequent reduction step. For instances, if something put on the amine is an urea, its solubility may be limited and a polar solvent such as tetrahydrofuran or N,N-dimethylformamide that is costly and environmentally unfavorable may be necessary. If a group put on the amine contains a reducible substituent such as halogen, carbonyl, cyano, or nitro group, the subsequent reduction step is complicated and unwanted by-products or impurities may be generated. Generation of such by-products or impurities in the reduction has a big impact on the subsequent steps. Particularly, the reduced intermediate, an aminophenol derivative, is too sensitive to handle and it is necessary to be used in the final step without isolation. The final step of the synthetic sequence is a ballasting step. A ballasted compound is usually difficult to crystallize and purify. Presence of by-products or impurities makes it even worse. Such a difficult and unclean final step reaction hurts greatly the yield of final product. A drop in the yield of final step has a big impact on the cost of manufacturing the coupler. This is another disadvantage in yield and cost.
(7) All of the difficulties and limitations described above make the cost of manufacturing the coupler so high. It is a major reason why only a limited number of 2-equivalent phenolic cyan-dye forming couplers have been commercialized.
It is therefore desirable to develop a new intermediate and synthetic route that alleviates the difficulties and limitations associated with the prior art and helps to simplify and reduce the cost of manufacturing phenolic cyan-dye forming couplers.
SUMMARY OF THE INVENTION
The present invention provides 4-acylamino-2-hydroxy-5-substituted-acylanilides of the general formula I:
wherein
R is hydrogen or an alkyl group,
Y is a group linked to the rest of the compound by a —O—, —S—, or —N— atom;
and
R′ is a ballast group.
In another aspect this invention relates to a method of making 2-equivalent phenolic cyan-dye forming couplers, the method comprising the step of deblocking the 2-acyl group by hydrolysis and preferrably then acylating to append a substtituent such as a photographically useful group on the amine at the 2-position.
The compounds of Formula I and the method provide a common intermediate from which a variety of 2-equivalent phenolic cyan-dye forming couplers can be prepared using a simple process and from readily available intermediates.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides new intermediates and new synthetic method involving ‘Ballast Amide First and Urea Last’. Advantages of making couplers with the new intermediates and the new synthetic method are multifold.
(1) N-Acyl amine present at 2-position exerts an induction effect to activate 5-position of the ring. Therefore, nitration can be done cleanly using a dilute nitric acid in environmentally favorable solvent such as water or acetic acid. This is an advantage in environment, safety, yield, and cost.
(2) Presence of an N-acyl group also assists to reduce thermal insta
Eastman Kodak Company
Gerstl Robert
Kluegel Arthur E.
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