PHOTOGRAPHIC COLOR COUPLERS, PHOTOGRAPHIC MATERIALS CONTAINING THEM AND METHOD OF FORMING DYE IMAGES

Abstract: Novel photographic dye-forming couplers comprise an imidazo[1,2-b]pyrazole nucleus which reacts at its 3-position with an oxidized aromatic primary amino color developing agent. These couplers are monomeric or polymeric and are useful in photographic materials and processes and have improved absorption and solubility characteristics.

Description: PHOTOGRAPHIC COLOR COUPLERS. PHOTOGRAPHIC .MATERIALS CONTAINING THEM AND METHOD OF FORMING DYE IMAGES This invention relates to a new class of photographic color couplers comprising an iaidazo- [1.2-b]pyrazole nucleus, to photographic materials containing them and to a method of forming a dye image in such photographic materials. A number of nitrogen-containing heterocyclic compounds have been proposed for color couplers. Pyrazolone couplers, for example, are widely used as magenta dye-forming couplers. Other couplers are described in Bailey and Williams. "The Photographic Color Development Process" in the Chemistry of Synthetic Dyes. ed. K. Venkatara an, Academic Press. Inc., New York and London. Volume 4. 341 (1971). Further couplers are the pyrazolo[3,2-c.]-s.-triazoles and imidazo[1.2-b.]-ε-triazoles described in The Theory , of the Photographic Process, ed. T.H. James. Macmillan. New York, page 358 (1977) and Research Disclosure No. 16216. 1977. 73-75 respectively. Research Disclosure 24531 (September 1984) published by Industrial Opportunities Ltd.. The Old Harbourmaster's. 8 North Street, E sworth. Hants POlO 7DD. U.K. contains, inter alia, a reference to couplers of the general formula: wherein X. is hydrogen or a coupling-off substi- tuent while R», R4 and Rs are hydrogen or one of a number of specified βubstituents. Structural formulae of specific couplers within this general formula are listed but no examples of their prepara¬ tion or use are given. The present invention provides novel dye- forming color couplers. According to the present invention there is provided a photographic color coupler which comprises an imidazo[1.2-b]pyrazole nucleus and which reacts at its 3-position with an oxidized aromatic primary amino color developing agent. Preferred couplers have the general formula: N N --X in which Ri and R2 are each hydrogen or a substituted or unεubstituted alkyl, a substituted or unsubstituted aryl. substituted or unβubstituted ' heterocyclic, hydroxy. nitrile, sulfone . acylamido. sulfonamide , sulfamoyl . alkoxycarbonyl, aryloxycarbonyl or nitro group, an amino or substituted amino group, a carbamoyl or substituted carbamoyl group, a non-coupling-off alkoxy group or a non-coupling-off phenolic stabilizer moiety. Rx is any of the groups which Ri and R2 may represent but is not hydrogen, and X is hydrogen or a group which splits off during coupling, and in which one of the substituents Ri. R2 or Rs optionally contains an ethylenically unsaturated polymerisable group. It is known that pyrazolotriazole (PTs) and pyrazolobenzimidazole (PBIs) dyes have better absorption characteristics (viz. less blue absorp- tion) than the corresponding pyrazolone dyes. The dyes from the couplers of the present invention also have good absorption properties, and since they have only two fused rings compared with the PBIs which have three, they have, in consequence, better solu- bility and thus are easier than PBIs to disperse in photographic emulsions. Furthermore, the couplers of the present invention in comparison with PT couplers have one extra site to carry an additional substit- tuent. This extra substituent can be used through electronic and steric effects to finely control parameters such as pK and reactivity. Hence higher activity couplers can be obtained from this new series of compounds. The absorption λaax can also be varied; the examples below show λaax variations from 529-620 nm. Examples of substituents Ri. Ra and Rs include alkyl radicals which may have a straight or branched chain and may be substituted and preferably contain 1-22 carbon atoms, e.g. methyl, ethyl, n-propyl, isopropyl, sec-butyl, tert-pentyl, n-hexyl or 2-aminoethyl; aryl radicals which may be substi¬ tuted, e.g. phenyl, 4-methylphenyl; heterocyclic radicals e.g. pyridyl or thienyl; aaino, aethylamino, diethylamino, phenylamino; acylamido radicals e.g. ethylcarbonamido. n-decylcarbonamido. phenylethylcar- bonamido. phenylcarbonamido: non-coupling alkoxy group or a non-coupling phenolic stabilizer moiety. e.g.. as described in U.S. Patent 3,519,429 (equiv¬ alent U.K. Specification 1,183.515). It is preferred that Rs represents a substituent which cannot be replaced by oxidized color developing agent, that is, not a coupling-off group. Examples of radicals which X may represent which split off during color development include: a halogen atom, e.g. F. C£. Br or I; -S0 3 H; -COOH; R4-0 or R4-S- wherein R4 is an alkyl. aryl or heterocyclic radical which may bear substituents e.g. phenyl. tolyl, tetrazolyl; amino or substituted amino. e.g. aethylamino, diethylamino or phenylamino, or any of the substi- tuted amino groups described in British Specification 1.520.551; acyloxy; βulfonyloxy ; or heterocyclic, for example hydantoin, imidazopyra- zoles. pyrazolo-triazoles. imidazo-s.-triazoles. a phthalimido or benzotriazole. Further groups that X may represent are the radicals of a photographically useful compound which compound is released on coupling. Examples of such compounds include development inhibitors, development accelerators, developing agents, electron transfer agents, color couplers and azo dyes. Examples of such X groups include: -S-alkylene-COOH Rs I wherein Rs is aromatic, heteroaromatic. or alkyl. e.g. phenyl. ethyl, t-butyl or pyridyl. In some applications Rs may be a ballasting group which would render the coupler, and after coupling. * the coupling-off group, nondiffusible. The alkylene group may be straight chain or branched and. again, could be a ballasting group. Alternatively the radical of the photo¬ graphically useful compound (PUC) may be linked via a group which aids the release of the compound by means of anchimeric assistance. An example of such a group is: (CH 2 ) n -N-C0-PUC iso-propyl Other similar groups are described in British Patent Specification 2.010.818. If the present couplers are to be incorpor¬ ated into a photosensitive photographic material, they will normally contain a ballast group to render them nondiffusible. Examples of such ballast groups include alkyl groups of 8-22 carbon atoms. The ballast may be attached directly or indirectly in the 2. 6 of 7-position in formula (I). A preferred class of the present couplers have the formula: N N *-X wherein R» is a substituted or unsubstituted alkyl group of 1-22 carbon atoms. B.7 is a substituted or unsubstituted alkyl or alkylcarba oyl group in which the alkyl group has 1-22 carbon atoms, and Rs is hydrogen or an alkyl or aryl group either of which is substituted or unsubstituted. and X is as defined above. Another preferred class of color couplers comprise an imidazo[l,2-b_]pyrazole nucleus which reacts at its 3-position with an oxidized aromatic primary amino color developing agent and which ■ -:- contains an ethylenically unsaturated polymerizable group. A preferred group of such color couplers: have the general formula (I) above and contain a substituent comprising a polymerizable ethylenically unsaturated group. Such a group may be attached directly or indirectly to the fused ring nucleus of the coupler. Such couplers have the general foraula: X in which Ri and Ra are each hydrogen or a substituted or unsubstituted alkyl. a substituted or unsubstituted aryl, a substituted or unβubβtituted heterocyclic, hydroxy, nitrile, sulfone , acylamido, sulfonaroide . sulfamoyl . alkoxycarbonyl, aryloxycar- bonyl or nitro group, an amino or substituted amino group, a carbamoyl or substituted carbamoyl group, a non-coupling-off alkoxy group or a non-coupling-off phenolic stabilizer moiety. Rs is any of the groups which Ri and Ra may represent but' is not hydrogen, and X is hydrogen or a group which splits off during coupling, and in which one of the substituents Ri, R2 or Rs contains an ethylenically unsaturated polymeri¬ zable group. When indirectly linked the polymerizable group is attached via a linking group which may contain alkyl or aryl moieties, groups of the formula -0-. -S-. -CO-. -S0 2 -. -NH-. -NHCO-. -NHS0 2 -. -CONH- and -SO„NH- or any combination thereof. 2 In particular the polymerizable couplers may be of general formula (I) in which Ri r R2 has the formula: ~ * \•» -•t — H - C0CR4 » CH2 (IV) or in which Rs has the formula: - CONH \ •»-•7- NH - C0CR4 - CH2 (V) wherein R4 is hydrogen or methyl. The present couplers, especially those without polymerisable groups, may be prepared using the following routes: Scheme 1 An alternative method of obtaining couplers of formula I wherein Rs is -CN is : Scheme 2 CCft RiCOCH CN s CN 2 NaOAc Ri CC1 s NH i Hydrazine hydrate o ( I I I ) H Coupler (III) may also be used to prepare amides containing a ballast group via an intermediate aldimine thus: Scheme 3 Coupler (III)→ The method of preparation described above allow the present couplers to be prepared efficiently in the minimum number of steps and in good yields. The poly eriβable couplers may be prepared by one of the following reaction scheaes: Scheme 4 Rs Rs C1COC - * • CH R« CH or N N- Using the starting compound, the procedure is analo- gous to Scheme 1. Scheme 5 N N- \ The following Table I lists specific exam- pies of couplers according to Formula I. TABLE I N N — Coupler No . X R 1 Rl 1 -H - Bu -Me -CN -H -t •- •' Bu •C0 2 Et 3 -H -H - -CN Bu 4 -H ■ H -t -CONH 2 Bu 5 -H -H -t -C0 2 Et Bu -OPh -t Bu -C0 2 Et w ω ■ J ■u • ω ω o •N N υ o o o I i w e o_) I I 3 3 øa CO 3 β α * I •U I I X I X XI I X I υ X I I TABLE I (con't) Coupler No. X R 1 R 2 R_ • m • / \ 11 -H -NO 2 -Ph -C0 2 Et c 1 _w 33 14 -OPh -Ph -NHCOC 1 6 H 33 -CN 15 -CΛ -NHPh -CA \ »m • / \ \ υ z I P-l C X o ϋ O i // ^ o // . X U - ϋ - O — - W -• •- O X \ / \ / w • -=• t- I β < - I • • oil • • •:_.• / \ TABLE I (con't) Coupler No. X R^ R^ R^ OMe / 17 -N-N- « ^-OMe - « ζ ^-CONH-CH-Ci 2 H 2 s- -Me -Me O TABLE I (con't) Coupler No, R 1 Ph t- herein Is tertiary-butyl. Me herein lβ methyl. Et herein Is ethyl. Ph herein is phenyl. A specific preparation is as follows: Scheme 6 t BuCOCH Br H Substituent X (the leaving group in 2-equiv- alent couplers) may be introduced into the appropri¬ ate intermediate or added to the preformed imidazo- [1.2- pyrazolβ viz. for incorporation during ring formation: Scheme 7 or for incorporation on the preformed coupler: Scheme 8 N N • N N « N ca The present polymerizable compounds may be polymerized alone or with one or more comonomers to form a polymeric color coupler. The present inven¬ tion also provides such couplers. A preferred polymeric color coupler of the present invention has the formula: wherein Rs is hydrogen or methyl, R7 is alkyl of 1-5 carbon atoms which may be substituted. R« is the radical of a coupler of formula (la), n is 50-100*. and m is 0-50%. Preferred comonomer units are derived from ethylacrylate. butylacrylate and/or ethoxyethyl acrylate. The dye-forming couplers of this invention can be used in the ways and for the purposes that dye-forming couplers have been previously used in the photographic art. They may be dissolved in process¬ ing solutions (unballasted) or incorporated into photographic materials (normally ballasted). Typically, the couplers are incorporated in silver halide emulsions and the emulsions coated on a support to form a photographic element. Alterna¬ tively, the couplers can be incorporated in photo¬ graphic elements adjacent the silver halide emulsion where, during development, the coupler will be in reactive association with development products such as oxidized color developing agent. Thus, as used herein, the term "associated therewith" signifies that the coupler is in the silver halide emulsion layer or in an adjacent location where, during processing, it will come into reactive association with silver halide development products. The photographic elements can be a single color elements or multicolor elements. In a multi¬ color element, the magenta dye-forming couplers of this invention would usually be associated with a green-sensitive emulsion, although they could be associated with an emulsion sensitized to a different region of the spectrum, or with a panchromatically sensitized, orthochromatically sensitized or unsensi- tized emulsion. Multicolor elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders, as known in the art. A typical multicolor photographic element would comprise a support bearing a cyan dye image- forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, at least one of the magenta dye-forming couplers being a coupler of this invention, and a yellow dye image-forming unit comprising at least one blue- sensitive silver halide emulsion layer having associ¬ ated therewith at least one yellow dye-forming coupler. he element can contain additional layers. such as filter layers. In the following discussion of suitable materials for use in the emulsions and elements of this invention, reference will be made to Research Disclosure. December 1978. Item 17643. published by Industrial Opportunities Ltd., The Old Harbourmaster's, 8 North Street, Emsworth, Hants POlO 7DD. U.K., the disclosures of which are incor¬ porated herein by reference. This publication will be identified hereafter as "Research Disclosure". The silver halide emulsion employed in the elements of this invention can be either negative- working or positive-working. Suitable emulsions and their preparation are described in Research Disclo¬ sure Sections I and II and the publications cited therein. Suitable vehicles for the emulsion layers and other layers of elements of this invention are described in Research Disclosure Section IX and the publications cited therein. In addition to the couplers of this inven¬ tion, the elements of the invention can include additional couplers as described in Research Disclo- sure Section VII. paragraphs D, E, F and G and the publications cited therein. The couplers of this invention and any additional couplers can be incor¬ porated in the elements and emulsions as described in Research Disclosures of Section VII. paragraph C and the publications cited therein. The photographic elements of this invention or individual layers thereof, can contain brighteners •I (see Research Disclosure Section V), antifoggants and stabilizers (see Research Disclosure Section VI). antistain agents and image dye stabilizer (see Research Disclosure Section VII, paragraphs I and J). light absorbing and scattering materials (see Research Disclosure Section VIII). hardeners (see Research Disclosure Section XI). plasticizerβ and lubricants (see Research Disclosure Section XII), antistatic agents (see Research Disclosure Section XIII). matting agents (see Research Disclosure Section XVI) and development modifiers (see Research Disclosure Section XXI). The photographic elements can be coated on a variety of supports as described in Research Disclo¬ sure Section XVII and the references described therein. Photographic elements can be exposed to actinic radiation, typically in the visible region of the spectrum, to form a latent image as described in Research Disclosure Section XVIII and then processed to form a visible dye image as described in Research Disclosure Section XIX. Processing to form a visible dye image includes the step of contacting the element with a color developing agent to reduce developable silver halide and oxidize the color developing agent. Oxidized color developing agent in turn reacts with the coupler to yield a dye. Preferred color developing agents are p-phenylene diamines. Especially preferred are 4-amino-N,N-diethylaniline hydrochloride. 4-amino- 3-methyl-N-ethyl-N-β-(methanesulfonaraido)- ethylaniline sulphate hydrate, 4-amino-3-methyl-N- ethyl-N-β-hydroxyethylaniline sulphate, 4-amino- 3-β-(methanesulfonamido )ethyl-N,N-diethylaniline hydrochloride and 4-amino-N-ethyl-N-(2-methoxy- ethyl)-m-toluidine di-p-toluene sulfonate. With negative-working silver halide emul- sionε this processing step leads to a negative image. To obtain a positive (or reversal) image. this step can be preceded by development with a non-chromogenic developing agent to develop exposed silver halide. but not form dye, and then uniform fogging of the element to render unexposed silver halide developable. Alternatively, a direct positive emulsion can be employed to obtain a positive image. Development is followed by the conventional steps of bleaching, fixing, or bleach-fixing, to remove silver and silver halide. washing and drying. In assessing the usefulness of the present couplers, a number of properties can be determined. The wavelength of maximum absorption of a dye solution (λmax) and the half bandwidth (HBW) can be determined by well known procedures. For the purposes of determining pK. it is assumed that the coupler C-H. where C is the radical of the coupler is ionized, thus: [C~][H + _ a [CH] and pK is minus log, Λ K . a -"lO a In determining solution activity, measure¬ ments are taken of the rate at which coupler is consumed under specified test conditions: where [D ] is the concentration of oxidized color developer. Alternatively: d[C] dt k c -α[C][D oχ ] whence .it can be seen that α « t : ■C -, " . ] -. In Table II below, the values of pKa, log Kc and log K -α are given, c The following examples are included for a better understanding of the invention. Example 1 (Coupler 2) Following the method of scheme 1 above, the compound of the formula: H (8.1 g: 0.03 moles) was mixed with bromopinacolone (5.2 g; 0.06 moles), tetramethylgυanidine (3.24 g; 0.03 moles) and acetonitrile (162 ml). The mixture was heated to reflux and maintained at that tempera¬ ture for 20 hours. Solvent removal and column chromatography [silica; ethyl acetate (75%)/petrol 60-80 (25*)] afforded the desired product as a yellow solid: 81\ yield, mpt. 187-188°C. C H N Found 59.3 5.8 15.4 Requiresf 59.2 5.5 15.3 tAnalysis for 0.5M water of crystallization 3-Arainopyrazoles may be obtained from one of several general methods which are outlined in the following references: 1) L.C. Behr. F. Fusco and CH. Jarboe "Pyrazoles. pyrazolines. pyrazolidines. indazoles and condensed rings", ed. R.H. Wiley, Interscience. New York, 1967; 2) M.H. Elnagdi et al, J. Heterocycl. Chem. 1979, 16., 1109; 3) R. Gompper and W. Tδpft. Chem. Ber.. 1962. £5.. 2861. 2871, 2877. α-Haloketones are described throughout the literature, however several general texts contain references to their preparation. Amongst these general texts are: 1) R.D. Chambers and S.R. James in "Comprehensive Organic Chemistry." ed. DHR Barton and W.D. Ollis. Pergamon Press, Oxford. 1979. vol. 1. p. 491; 2) M. and L.F. Fieser in "Reagents for Organic Synthesis". Wiley. New York. 1974. vol. 4. p. 138; 3) "The Chemistry of the Carbon-Halogen Bond, part 2". ed. S. Patai. Wiley. New York. 1973; 4) "Organic Reactions", ed. R. Adams et al. Wiley. New York. 1947, 4th printing, vol. 1. p. 1; 5) "Organic Reactions", ed. J. Baldwin et al, Wiley, New York, 1975, p. 423. Example 2 A number of other compounds are prepared by the method of Example 1 except for Couplers (1) and (3) in which the pyrazole was obtained by the method shown in scheme (2). The λmax EtOAc. and half- band width are given for the derived dye. where the developer moiety is that derived from the developer 4-N-ethyl-N-(β-methanesulfonamidoethyl)amino-o- toluidine sesquisulfate (CD3). Solution activity parameters log k -α and log k - at pH 10 and 20°C and pKa measurements were also recorded for representative imidazo- [1.2-b]pyrazoles. Solution activity was measured using the βtop-flow method of Tong [e.g. L.K.J. Tong. J. Phyε. Chem.. 1954. ____. 1090-97 (Comm. 1649)]. The contents of the two input syringes were: Solution A Color developing agent CD3 1 x 10 " mol. Coupler (O.lt ethanolic solution) 10 ml. Solvent buffer* 11 pH adjusted with H 2 S0 4 or NaOH to pH 10 Solution B Potassium ferricyanide 2.1 x 10 mol. Solvent buffer* 11 pH as A *Solvent buffer was Triton X (TX-100) 30 g (3% aqueous solution) sodium carbonate 20 g water 11 pKa Measurements used the method of Albert and Serjeant ("The Determination of lonization Constant", Chapman and Hall, 1971). The word Triton is a trademark. Analytical results, yield, solution activity and pKa data are recorded in Table II. TABLE II EtOAc Coupler REQUIRES FOUND Yield λπax HBW pKa log log k c -α No. C H N C H N % (nm) (nm) kc-α 1 65.3 6.98 27.76 65.4 7.0 27.7 54 538 88 9.5 5.4 — 4- 2 59.2 5.5 15.3 59.3 5.8 15.4 81 546 93 11.8 3.46 - 3 4 57.0 6.7 26.6 57.4 7.0 25.4 14 538 95 >11.8 4.88 - 5 61.2 7.3 17.9 60.1 7.1 17.5 16 536 107 11.8 3.98 5.78 64.3 5.4 12.5 62.9 5.6 11.6 77 538 88 9.5 5.10 7 65.3 6.6 16.3 65.7 6.3 16.0 67 538 97 >11.8 3.78 - TABLE II (con't) EtOAc Coupler REQUIRES FOUND Yield λmax HBW pKa log log k c -α No. C H N C H N % (nm) (nm) k c -α + :- 8 65.4 7.8 9.1 65.5 7.9 9.1 54 538 90 >11.8 3.41 θ 9 53.4 4.7 13.3 53.2 5.2 13.8 61 547 90 10.8 4.16 5.29 10 56.5 4.4 17.6 56.6 4.8 17.3 16 543 89 - • θ 11 61.6 4.1 14.4 61.4 4.1 14.0 45 579 101 11.0 4.86 6.16 12 - 602 108 - ♦Analysis for 0.25M water of crystallization +Analyβlβ for 0.5M water of cryβtalllzatlon ΘAnalyβlβ for 0.75M water of cryβtalllzatlon Example 3 Coupler (8) of the formula: N N • was dispersed in di-n-butyl phthalate (1:1 by weight) and coated in the following format: Bis-vinylsulphonyl- O.OOβg.m -2 methyl ether (BVSME) AgCSt (undyed) 0.538g.m -2 Antifoggant 0.014g.m -2 Coupler 0.69m.mole.m~ a (xg.m "2 ) di-n-butyl phthalate xg.m -2 Gelatin 3.225g.m -2 Poly(ethylene terephthalate) base Check coatings of the known Coupler B instead of Coupler (8) in the same format were prepared for comparative purposes. This compound is typical of a pyrazolone coupler used in a photo¬ graphic product. Coupler (B) Exposed strips were processed to yield a good magenta dye image having an absorption maximum of 555 nm. Dye density measurements obtained from the process strips are given below: λmax dye yield at λ ax (8) 555 1.17 _B) 536 1.21

Claims: WHAT IS CLAIMED IS: 1. A photographic color coupler which comprises an imidazo[l,2-b]pyrazole nucleus and which reacts at its 3-position with an oxidized aromatic primary amino color developing agent. 2. A color coupler as in claim 1 which has the general formula: N N » X (I) in which Riand Ra are each hydrogen or a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, a substituted or unsubstituted heterocyclic. hydroxy. nitrile. sulfone. acylamido. sulfamide, sulfa oyl. alkoxycarbonyl, aryloxycarbonyl or nitro group, an amino or substituted amino group, a carbamoyl or substituted carbamoyl group, a non-coupling-off alkoxy group or a non-coupling-off phenolic stabilizer moiety. Rs is any of the groups which Ri and R2 may represent but is not hydrogen, and X is hydrogen or a group which splits off during coupling. and in which one of the substituents R . R2 or R* optionally contains an ethylenically unsaturated polymerisable group. 3. A color coupler as in claim 2 in which X is a halogen, sulfo. carboxy, R«-0-. R4-S- wherein R is a substituted or unsubsti¬ tuted alkyl or aryl group or an amino or substituted amino group or an acyloxy. sυlfonyloxy or benzotria- zolyl group, or an azo radical rendering the coupler colored. 4. A color coupler as in claim 2 in which the group X. when released from the coupler, forms a photographically useful compound. 5. A color coupler as in claim 4 in which the photographically useful compound is a development inhibitor. 6. A color coupler as in claim 2 in which Ri. Ra and R3 represent a straight or branched chain alkyl group having 1-22 carbon atoms. 7. A color coupler as in claim 1 which is a compound selected from the group consisting of: N N — X Coupler No, X R H!_ 1 -H -t Bu -Me -CN -H " >-N0 2 -t -C0 2 Et ^ __.___. •__' Bu I 3 -H -H -t Bu -CN 4 -H •H -t Bu -CONH 2 5 -H •H -t Bu -C0 2 Et -OPh "") • -•«> • -t Bu -CO.Et 8. A photographic element comprising a support and a photographic silver halide emulsion having associated therewith a color coupler which comprises an imidazo[1.2-b_]pyrazole nucleus and which reacts at its 3-position with an oxidized aromatic primary amino color developing agent. 9. A photographic element as in claim 8 wherein said color coupler has the general formula: N N « N X (I) in which R and Ra are each hydrogen or a substituted or unsubstituted alkyl. a substituted or unsubstituted aryl. heterocyclic. hydroxy. nitrile., « sulfone. acylamido. sulfamide. sulfamoyl. alkoxycar^ bonyl. aryloxycarbonyl or nitro group, an amino or substituted amino group, a carbamoyl or substituted carbamoyl group, a non-coupling-off group alkoxy group or a non-coupling-off phenolic stabilizer moiety. Ra is any of the groups which R and Ra may represent but is not hydrogen, and X is hydrogen or a group which splits off during coupling. 10. A photographic element as in claim 8 wherein X is a halogen, sulfo. carboxy. R4-0-. R4-S- wherein R4 is a substituted or unsubsti¬ tuted alkyl or aryl group or an amino or substituted amino group or an acyloxy, sulfonyloxy or benzotria- zolyl group, or an azo radical rendering the coupler colored. 11. A photographic element as in claim 8 wherein the group X, when released from the coupler, forms a photographically useful compound. 12. A photographic element as in claim 8 wherein the group X. when released from the coupler, forms a photographically useful compound which is a development inhibitor. 13. A photographic element as in claim 9 wherein R . Ra and Rs represent a straight or branched chain alkyl group having 1-22 carbon atoms. 14. A photographic element as in claim 8 wherein said color coupler is a compound selected from the group consisting of: <_ N -X Coupler No. X . R 2 • 1 -H X. y -NO a - Bu -C0 2 Et 2 -H H -t Bu -CN 3 -H H -t Bu ■ CONH 2 4 -H H -t Bu •C0 2 Et am • -OPh / \ y -NO a -t •* -.. y Bu -C0 2 Et 15. A process of forming a dye image in an exposed photographic element comprising a support and a photographic silver halide emulsion, said process comprising developing the photographic element with a silver halide color developing agent in the presence of a color coupler which comprises an imidazo- [l,2-b.]pyrazole nucleus and which reacts at its 3-position with an oxidized aromatic primary amino color developing agent. 16. A process as in claim 15 wherein the color developing agent is a p_-phenylenediamine. 17. A processed photographic element containing a magenta dye image comprised of a magenta dye obtained by coupling of oxidized silver halide color developing agent and a magenta dye-forming coupler which comprises an imidazo[l,2-b]pyrazole nucleus and which reacts at its 3-position with an oxidized aromatic primary amino color developing agent.

Inventors: BAILEY JOSEPH, ROGERS DAVID NEIL, BAILEY, JOSEPH, ROGERS, DAVID, NEIL
Applicants: EASTMAN KODAK CO, KODAK LTD, EASTMAN KODAK COMPANY, KODAK LIMITED
Application year: 1985
Main classification: G03C7
IPC codes: C07D487, G03C7