GB2073734A - Blocked Electron Transfer Agents - Google Patents

Abstract

Derivatives of 3-pyrazolidones are disclosed as photographic developing agents in U.K. Specification 1,093,281 and in U.S. Patents 3,312,550 and 3,453,109. The invention provides compounds of formula: <IMAGE> wherein R is a blocking group, wherein the group R.CO hydrolyses in alkaline aqueous solution and wherein R<1> is H or alkyl. Hydrolysis of the group R.CO produces an electron-transfer agent for developing a colour transfer photographic material. The compound is preferably incorporated in a dye-receiving element. It has the advantage of being stable in the presence of mordants.

Description

SPECIFICATION Blocked Electron Transfer Agents This invention relates to new chemical compounds and to new preparative methods. This invention also relates to photographic developing agents, particularly to electron transfer agents such as can be used in colour image transfer processes.

Derivatives of 3-pyrazolidones are disclosed as photographic developing agents in many patent specifications such as, for example, U. 1,093,281 and U.S. Patents 3,312,550 and 3,453,109. Still more 1 -phenyl-3-pyrazolodones are described and claimed in U.S. Application Serial No. 948063 filed 2 October 1 978 and European Application No. 79200530 filed 24 September 1 979.

In U.K. specification 1,093,281 there are described and claimed compounds of general formula I.

wherein R1 is a hydroxyalkyl group, R2 is hydroxyalkyl, alkyl or a substituted alkyl group in which the alkyl group or residue contains up to 4 carbon atoms and R3 is an aryl or substituted aryl group.

Specification 1,093,281 also described the preparation of various specific compounds of formula I e.g.

in which R, is methyl, R2 is hydroxymethyl and R3 is phenyl.

In U.S. Patent 3,312,550 certain photographic elements comprising a light-sensitive silver halide layer are described which contain a 3-pyrazolidone of formula I

in which the various R groups represent substituents such as H, alkyl, acyl, heterocyclic or aryl groups.

The list of typical substituents given in column 4 lines 70-75 of U.S. Patent 3,312,550 includes carboxylic acid acyl such as acetyl, benzoyl, nitrobenzoyl and haloacyl.

In U.S. Patent 3,453,109 there is described a method of producing a relief image by developing an unhardened silver halide emulsion with a composition containing a compound of formula

wherein R1 is H or a lower alkyl group such as hydroxymethyl, hydroxyethyl, hydroxypropyl, methyl, ethyl, propyl and the like.

In column 2 lines 27-33 of U.S. Patent 3,453,109 are described groups represented by R including methyl, ethyl, propyl and butyl substituted with carboxy or sulpho groups.

U.S. Patent 4,076,529 describes various photographic elements which are useful in colour diffusion transfer processes and which contain various non-diffusible redox dye-releasing compounds.

These compounds are cross-oxidised in an alkaline processing medium by oxidised electron transfer agents and, upon oxidation, react with the alkali and release a diffusible dye. The oxidised electron transfer agent is produced as the electron transfer agent itself (ETA) reduces the exposed silver halide to silver and, on cross-oxidising the redox dye-releasing compound, the oxidised electron transfer agent is converted back to the ETA.

There is now an interest in using colour image transfer processes for making colour prints from colour originals and in one printing process the exposed light-sensitive material containing the dyereleasing compounds (hereinbelow called the 'donor') is passed through an alkaline aqueous bath and then laminated with a receiving sheet containing a mordant for the dyes. The ETA may be dissolved in the bath or incorporated either in the donor or in the receiving sheet. In each of these locations the ETA undergoes unwanted changes.

Thus, in the bath, the aerial oxidation reduces the activity of the developer in a fairly short time and the oxidation products may cause random dye release from the donor by reaction with the dye carrier.

If the ETA is incorporated in the donor it may be leached out into the processing bath, where, besides being subject to aerial oxidation, it will alter the amount of ETA in subsequent donors passing through the same bath, thus preventing accurate process control.

The above disadvantages are eliminated by incorporation of the ETA into the receiver, but here ETAs have been found to be unstable to prolonged keeping especially in the presence of certain mordants which are otherwise highly desirable because they improve dye stability. After a few months keeping the amount of ETA may be so depleted as to reduce considerably the dye yield when the receiver sheet is used to make a print. This disappearance in the activity of the ETA is believed to be brought about by aerial oxidation to fully oxidised inactive species such as

We have found that 4-methy-4-hydroxymethyl-1 -phenyl-pyrazolidin-3-one and closely related ETAs can be stabilised for incorporation in a dye receiving element by acylation with certain blocking groups, especially those possessing a tertiary carbon atom linked to the carboxy group of the acylating reagent. Particularly high stability has been conferred when the acylation occurs in the 4hydroxymethyl group.

Thus certain electron transfer agents of this invention have the general formula

wherein R is a blocking group preferably possessing a tertiary carbon atom adjacent to the carboxylic ester group and R' is H or one or more simple alkyl groups such as methyl or ethyl.

Blocked ETAs of this type have been found to be stable to prolonged keeping when incorporated in a receiver together with mordant. Blocked ETAs of the above general structure in which R possesses anchimeric assistance to hydrolysis in alkaline solution have high stability and also give a higher dye yield than those without anchimeric assistance to hydrolysis.

U.K. application 7934892 filed on 8 October 1979 and the corresponding European application described and claims in claim 1 inter alia a photographic recording material comprising a layer containing . . . a photographic reagent wherein said ... reagent contains a blocking group ... which in said reagent is joined to an oxygen, sulphur, nitrogen, phosphorus or selenium atom, which blocking group under alkaline conditions is uniformly cleavable from said reagent by an intramolecular nucleophilic displacement reaction within said blocking group.

According to claim 21 of U.K. 7,934,892 said photographic reagent has the structure: PR-G'-E-X-NuP wherein PR-G' is the residue of a photographic reagent, G' being an oxygen, sulphur, selenium, phosphorus or nitrogen atom; E is an electrophilic group; NuP is a precursor of a nucleophilic group which, under alkaline conditions, is converted uniformly to a nucleophilic group; and X is a linking group for spatially relating E and NuP to enable, after conversion of NuP to a nucleophilic group, an intramolecular nucleophilic displacement reaction which cleaves the bond between G' and E.

According to claim 22 PR-G' is the residue of a development inhibitor, a silver halide developing agent, an electron transfer agent or a coupler.

U.K. 7,934,892 also describes carboxylic acid derivatives which can be used to acylate cyan dyes which derivatives may be represented by the following formulae:

(A) (B) (c) ( D) wherein each R=alkyl, aryl, or similar such group rendering steric hindrance or the two R's together complete a ring.

NuP=nucleophilic precursor (or masked nucleophile) which nucleophile is not oxidisable by oxidised developing agent, X=leaving group, e.g. Cl, OH, OR' (where R'=alkyl or aryl).

The carboxylic derivatives which are used include those more specifically represented by the following structures in which X=CI: Derivatives of General Formula (A)

wherein R is as above defined and R' is alkyl, for example CH3.

wherein R" is alkyl, substituted alkyl, aryl or substituted aryl, for example

wherein R is as above defined, n=0 or 1 and R"=alkyl e.g., CH3.

Derivatives of General Formula (B)

Derivatives of General Formula (C)

Derivatives of General Formula (D)

Such acid chlorides exhibit steric hindrance at the site of the carbonyl function and incorporate a masked nucleophile which can be activated at high pH.

Compounds (awl), (A2), (A3) and (D1) are new compounds.

Certain blocked electron transfer agents of the present invention can be prepared using carboxylic derivatives described above.

The following Examples 1, 2, 5 and 7 to 15 are examples of compounds of the invention and of their methods of preparation.

Examples are also given demonstrating the use of the compounds of the invention in dye imagereceiving materials. The preferred mordant in such receiving materials is a polyvinylimidazole partially (e.g. 10%) quaternised with chloroethanol. Such mordants are described in U.K. Specification 1,468,460 and Research Disclosure 12045 April 1974.

The Examples demonstrate preferred values of R' in the general formula of the compounds of the invention namely H, CH3 and C2H5 and preferred values of R, namely (CH3)3C-, C6H5CH20-,

The starred groups are groups which provide anchimeric assistance in the alkaline hydrolysis of the compounds of the invention. The first starred group may be modified by the replacement of each Cm, with another alkyl, e.g. C1~4, group.

The Examples also demonstrate the novel preparative method provided by this invention which comprises reacting a 4-hydroxymethyl-pyrazolidin-3-one with an acyl chloride in an inert solvent in the absence of a base at reflux. The inert solvent is preferably benzene or toluene. The reaction is continued until HCI ceases to be evolved.

In the Examples Me=CH3, Et=C2H5, PrA=isopropyl, Ph=phenyl, HMP means 4-hydroxymethyl-4- methyl-l -phenylpyrazolidin-3-one, TLC means thin layer chromatography and Rf means, in paper-strip chromatography, the proportion of the total length of climb of a solution that is reached by a spot characteristic of one of the constituents present.

Example 1 4-Methyl- 1 -phenylpyrazol idin-3-one-4-yl methylpivalate 4-Hydroxymethyl-4-methyl-1 -phenylpyrazolidin-3-one (HMP) (8.24 g, 0.04M) was dissolved in refluxing benzene (100 ccs) and pivaloyl chloride (4.82 g, 0.04M) added. Refluxing was continued until hydrogen chloride evolution almost ceased, (3 hours). Rotary evaporation of the benzene solution at 500 left a brown solid (11.51 g), which was recrystallized from ethanol (25 ccs) to give a white solid MP 120--125 OC (7.1 8 g, 62%). A second crop of crystals was recrystallised once more from ethanol to give a white solid MP 117-121 (0.88 g, 8%).

C,6H22N203 requires: C 66.18, H 7.64, N 9.65% found: C 66.07, H 7.65, N 9.60%.

Example 2 4-Benzyloxycarboxymethyl-4-methyl-l -phenylpyrazolidin-3-one 4-Hydroxymethyl-4-methyl-1 -phenylpyrazolidin-3-one, (10.31 g, 0.05M), and triethylamine, (5.5 g, 0.055 M), were dissolved in tetrahydrofuran (80 ccs) and stirred at room temperature while benzyl chloroformate, (8.53 g, 0.05M), was dripped in over 1 hour. The mixture was stirred for 6 days and the precipitated triethylamine hydrochloride filtered off. Evaporation of the filtrate left a yellow syrup, (18.47 g). Seed crystals of the desired compound were obtained by chromatographing a small sample of the syrup on a 'Florisil' column, eluting with 10% ethyl acetate in benzene and monitoring the eluent by T.L.C. on silica eluting with 30% ethyl acetate in benzene. After eluting two minor products giving spots on T.L.C. Rf 0.84 and 0.77 the column eluant was changed to pure ethyl acetate and the main product eluted to give a spot Rf 0.39 on T.L.C. On evaporation this fraction gave a gum which after standing for a week crystallised.

The crude syrup obtained from the reaction was dissolved in ethanol (100 ccs), seeded with these crystals, and allowed to evaporate slowly at room temperature. After some days white needle crystals MP 110-1 120C (3.37 g, 20%) were obtained in two crops.

C,6H22N203 requires: C 67.04, H 5.92, N 8.23% found: C 67.08, H 6.06, N 8.2% Example 3 4Hydroxymethyl-4-methyl-I -phenyl-2-pyrazolin-3-yl pivalate 4-Benzyloxycarboxymethyl-4-methyl-1-phenylpyrazolidin-3-one (1.7 g, 0.005 M), obtained in Example 2 above, and triethylamine (0.55 g, 0.0055 M) were stirred at room temperature in tetrahydrofuran (7 ccs), while pivaloyl chloride, (0.62 g, 0.0051 M), was dripped in over a few minutes.

After stirring at room temperature for 5 days the precipitated triethylamine hydrochloride was filtered off and the filtrate rotary evaporated at 500C leaving a pale yellow syrup (2.2 g). This was dissolved in tetrahydrofuran (40 ccs) and hydrogenated at room temperature and pressure using 10% palladium on charcoal (0.4 g) as catalyst. After 121 hours the catalyst was filtered off through kieselguhr and the filtrate rotary evaporated at 800C leaving a viscous pale yellow liquid (1.44 g, 99%).

C1gH20N204 requires: C 66.18, H 7.64, N 9.65% found: C 65.52, H 7.62, N 8.65%.

The mass spectrum gave a molecular ion at 290 as required.

Examples 4 and 5 4-Hydroxymethyl-4methyl-1-phenyl-2-pyrazolin-3-yl N-methyl-N-(2-methylphthalimid-4-yl) carbamate. 4-Methyl-I -phenylpyrazolidin-3-one-4-ylmethyl N-methyl-N-(2-methylphthal imid-4- yl)carbamate) - 4-Hydroxymethyl-4-methyl-1-phenylpyrazolidin-3-one, (4.15 g, 0.02 M) was dissolved in hot triethylamine and N-methyl-N-(2-methylphthalimid-4-yl)carbamoyl chloride (5.05 g, 0.02 M) added.

The mixture was refluxed 2 hours and the excess triethylamine rotary evaporated off. The residue was extracted with tetrahydrofuran when triethylamine hydrochloride remained undissolved and was filtered off. Evaporation of the filtrate left a brittle yellow glass (7.87 g). This mixture was separated by high pressure liquid chromatography on a silica column eluting with dichloromethane and an increasing proportion of ethyl acetate, under a pressure of about 8 atmospheres. The first fractions gave on evaporation 2-methyl-4-methylaminophthalimide, a yellow, fluorescent solid MP 1 28-1 500C. The next fraction gave a very small amount of 4-methyl-1 -phenylpyrazol-4-yl N-methyl-N-(2methylphthalimid-4-yl)carbamate contaminated with other products. The next fractions on evaporation yielded a brittle pale yellow glass consisting of 4-hydroxymethyl-4-methyl-1 -phenyl-2-pyrazolin-3-yl N-methyl-N-(2-methylphthalimid-4-yl)carbamate, (2 g, 24%), Example 4.

C22H22N405 requires: C 62.55, H 5.25, N 13.26% found: C 61.55, H 5.05, N 12.97%.

The mass spectrum gave a molecular ion at 422 as required.

Further elution of the column gave after a few minor products a fraction which in evaporation yielded 4-methyl-I -phenylpyrazolidin-3-one-4-ylmethyl N-methyl-N-(2-methylphthalimid-4-yl) carbamate as a brittle pale orange glass (1.5 g, 18%) Example 5.

C22H22N405 requires: C 62.55, H 5.25, N 13.26% found: C 61.70, H 5.26, N 12.96%.

The mass spectrum gave a molecular ion at 422 as required.

Examples 6 and 7 4-Hydroxymethyl-4-methyl-1 -phenyl-2-pyrazolin-3-yl Isodehydroacetate and 4-Methyl-I - phenylpyrazolidin-3-one-4-ylmethyl Isodehydroacetate Isodehydroacetyl chloride Isodehydroacetic acid (10.1 g, 0.06 M) was refluxed for 20 minutes in thionyl chloride (20 ccs), and excess thionyl chloride removed by rotary evaporation. Last traces of thionyl chloride were removed by adding benzene to the residue and rotary evaporating again. The brown solid residue, (11.2 g), was recrystallised from 40-60 petroleum ether (200 ccs), decanting the hot solution from an insoluble brown tar. On cooling, off white needles MP 53-570C (9.7 g), were deposited. A second crop with the same MP (0.65 g) was obtained. Total yield 10.35 g, 92%.

C8H7ClO3requires: C 51.49, H 3.78, Cl 19.00% found: C 51.56, H 3.86, Cl 19.09%.

4-Hydroxymethyl-4-methyl-1-phenyl-2-pyrazolin-3-yl Isodehydroacetate'and 4-Methyl-1- phenylpyrazolidin-3-one-4-ylmethyl Isodehydroacetate 4-Hydroxymethyl-4-methyl-1-phenylpyrazolidin-3-one, (4.12 g, 0.02 M) was dissolved in hot toluene (25 ccs) and a solution of isodehydroacetyl chloride, (3.73 g, 0.02 M), in 35 ccs of warm toluene added. The mixture was refluxed till hydrogen chloride evolution ceased, (3 hours), and the toluene solution was then decanted from an insoluble gum on the flask walls. The toluene was rotary evaporated off at 700C leaving a viscous yellow oil, (5.15 g). This mixture was resolved into four fractions by high pressure liquid chromatography on a silica column eluting with dichloromethane and an increasing proportion of ethyl acetate under-about 8 atmospheres pressure.

The first fraction contained an acylated derivative of oxidised HMP obtained as a crystalline solid which after recrystallisation from methanol gave cream needles MP 136-1 390C.

The second fraction on evaporation gave an amber glass which proved to be a diacylated derivative of HMP.

Evaporation of the third fraction gave 4-hydroxymethyl-4-methyl-1 -phenyl-2-pyrazolin-3-yl isodehydroacetate as a brown oil (0.66 g, 9%), Example 6.

C19H20N2O5 requires: C 64.03, H 5.66, N 7.86% found: C 62.73, H 5.75, N 7.04%.

The mass spectrum gave a molecular ion at 365 as required.

The fourth fraction on evaporation yielded 4-methyl-1-phenylpyrazolidin-3-one-4-ylmethyl isohydroacetate as a yellow glass, (1.14 g, 16%), Example 7.

C1gH20N205 requires: C 64.04, H 5.66, N 7.86% found: C 63.05, H 5.82, N 7.23%.

The mass spectrum gave a molecular ion at 356 as required.

Example 8 4-M ethyl3-oxo-l -phenylpyrazol idin-4-ylmethyl 3-ethoxycarbonyl-2,2-dimethylpropionate 3-Ethoxycarbonyl-2,2-dimethylpropionyl chloride This compound was prepared according to the method of H. E. Baumgarten and D. C. Gleason described in J. Org. Chem. 16,1658-68(1951).

Preparation of 4-Methyl-3-oxo-1-,phenylpyrazolidin-4-ylmethyl 3-ethoxycarbonyl-2,2dimethylpropionate. C19H26N2O5

3-Ethoxycarbonyl-2,2-dimethylpropionyl chloride (0.1 mole) was added to a solution of 4methyl-3-oxo-1 -phenylpyrazolidin-4-ylmethanol (20.6 g, 0.1 mole) in dry toluene heated under reflux.

The mixture was heated for 52 hours (Note 1).

The mixture was evaporated under reduced pressure and the residual oil dissolved in ethyl acetate. This solution was passed through a short 'Florisil' column to remove any residual HMP. The eluate was evaporated under reduced pressure to give an oil which was purified by column chromatography (Note 2).

The yield was 14.2 g (theoretical yield=36.2).

Notes 1) TLC analysis, (SiO2/glass, ethyl acetate/60-800 petrol 1:1 as eluant) showed some residual HMP.

2) 83 cmx2.5 cm SiO2 column using methylene chloride with an increasing proportion of ethyl acetate up to 50%, as eluant.

Example 9 4-Methyl-3-oxo-I -phenylpyrazolidin- 4-ylmethyl 4-(N-methyltrifluoroacetamido)-2,2dimethylbutyrate. 4(N-Methyltrifluoroacetamido)-2,2-dimethylbutyryl chloride The latter compound was prepared according to the method described in Example 13 of U.K.

Specification 7934892.

4-Methyl-3-oxo-1 -phenylpyrazol idin-4-yl methyl 4(N-methyltrifluornacetamido)-2,2- dimethylbutyrate. C20H26F3N3O4

4-(N-Methyltrifluoroacetamido)-2,2-dimethylbutyrylchloride (0.042 moles) was added to a solution of 4-methyl-3-oxo-1 -phenylpyrazolidin-4-ylmethanol (9.2 g, 0.045 mole) in dry toluene (60 ml) at reflux (Note 1). The mixture was heated for 13 hours (Note 2).

The solution was evaporated under reduced pressure to give an oil (20 g) which was purified by column chromatography (Note 3) to give the product.

The yield was 11.0 g (theoretical yield=1 8.0 g).

Notes 1) A solid separated from solution but gradually dissolved on further heating.

2) TLC analysis (SiO2/glass, ethyl acetate/6O-8O0C petrol 1:1 as eluant) showed only a trace of starting material.

3) 83 cmx2.5 cm SiO2 column using methylene chloride with an increasing proportion of ethyl acetate up to 50% as eluant.

Example 10 4-Methyl-3-oxo-l -phenylpyrazolidin-4-yl methyl-2-(N-isopropyltrifluoracetamidomethyl)phenylcarbonate 2-(N-lsopropylaminomethyl)phenol The compound was prepared as described in J. Heterocyclic Chem. 1976 13 667.

N-(2-Hydroxybenzyl )-N-isopropyltrifluoracetamide 2-(N-lsopropylaminomethyl)phenol (11 g, 0.0667 M), and dimethylaniline (16.2 g, 0.133 M), were stirred in tetrahydrofuran solution (200 ccs), while trifluoracetic anhydride (15.4 g, 0.0733 M), was dripped in over 1 5 minutes. After stirring a further 2 hour the solution was poured into dilute hydrochloride acid (1 I), and the oil which precipitated extracted with ethyl acetate. The ester layer was washed with brine, dried over magnesium sulphate, filtered, and evaporated below 400C leaving a red oil containing some -trifluoracetic acid. Water (200 ccs), was added and the mixture stirred rapidly till crystallisation took place. The crystals MP 90-91 0C (1 1 g, 63%) were collected and dried.

C12H,4F3NO2 requires: C 55.17, H 5.40, F 21.82, N 5.36% found: C55.13, H5.46, F21.30, N5.26% 2-(N-lsopropyltrifluroacetamidomethyl)phenyl chloroformate A solution of N-(2-hyd roxybenzyl)-N- isopropyltrifluoracetamide (2.61 g, 0.1 M), and dimethylaniline (1.21 g, 0.01 M), in toluene (5 ccs), was dripped into a stirred solution of phosgene (12.5%w/w), in toluene (12 ccs, 0.014 M of phosgene), at 0--5 OC over 4 hour. The solution was allowed to warm up to room temperature and stirred 48 hours. The precipitate of dimethylaniline hydrochloride was filtered off and the filtrate dried over magnesium sulphate. Filtration and rotary evaporation at 5O0C of the toluene solution left a yeliow-green oil (3.23 g, 1 00%) which was used in the next step without further purification.

C3H3CIF3NO3 requires: C 48.23, H 4.05, Cl 10.95, N 4.33% found: C 49.64, H 4.36, Cl 10.24, N 4.39% 4-Methyl-3-oxo-1 -phenylpyrazolidin-4yl methyl 2-(N-isopropyltrifluoracetamidomethyl)phenyl carbonate 2-(N-lsopropyltrifluoracetamidomethyl)phenyl chloroformate (3.02 g, 0.00933 M), and 4 Hydroxymethyl-4-methyl-1-phenylpyrazolidin-3-one (1.92 g, 0.00933 M), were refluxed in toluene (25 ccs) for 4 hours until hydrogen chloride evolution ceased. On cooling crystals of 2-(Nisopropylaminomethyl)phenyl hydrochloride (0.46 g; 24%), separated and were filtered off. Evaporation of the filtrate left a viscous oil (4.53 g). This was chromatographed on a 'Florisil' column (400 g), eluting with 30% ethyl acetate in cyclohexane and monitoring the eluant by thin layer chromatography on a silica plate eluting with 50% ethyl acetate in cyclohexane. The first 400 ccs from the column contained a mixture giving three spots on the thin layer plate Rf 0.81, 0.76 and 0.55. The next 200 ccs contained more of the third component (Rf 0.55), whilst the next 200 ccs contained nothing. The next 200 ccs contained the desired product giving a single spot on the thin layer plate Rf 0.40. The column eluant was changed to 50% ethyl acetate in cyclohexane and the next litre contained more of the desired product giving a single spot on thin layer chromatography Rf 0.40. The subsequent eluant from the column contained mixtures. The eluants containing the desired product were combined and rotary evaporated at 600C leaving a pale yellow gum (1.8 g, 41%), which on standing for a few days crystallised. A sample recrystallized from ethyl acetate gave a MP 1 48-1 5O0C.

C24H26F3N305 requires: C 58.41, H 5.31, F 11.55, N 8.52% found: C 58.31, H 5.39, F 11.25, N 8.50%.

Example 11 4Methyl-3-oxo-l -phenylpyrazolidin-4-ylmethyl benzoate 4-Hydroxymethyl-4-methyl-1-phenylpyrazolidin-3-one, (10 g, 0.0485 M), and benzoyl chloride (6.82 g, 0.0485 M), were refluxed in toluene (100 ccs), for 6 hours and then cooled to room temperature. After standing for three days white needle crystals MP 1 50-1 550C (2.72 g), separated and were collected. Concentration of the filtrate to about 25 ccs yielded a second crop (2.70 g), MP 135-1 500C. Evaporation of the mother liquor left a viscous liquid which deposited a small third crop of sticky crystals. Recrystallisation of the first two crops once and the third crop twice from toluene gave white needles MP 1 57-1 590 (4.08 g, 27%).

C,8H18N203 requires: C 69.66, H 5.85, N 9.03% found: C 69.43, H 5.83, N 9.06%.

Example 12 4-Methyl-3-oxo-1 -(4-tolyl)pyrazolidin-4-yl methyl pivalate Pivaloyl chloride (2.41 g, 0.02 M) and 4-hydroxymethyl-4-methyl-1-(4-tolyl)pyrazolidin-3-one (4.41 g, 0.02 M), were refluxed in toluene (30 ccs) for 2 hours when the evolution of hydrogen chloride had become negligible. A little solid was filtered from the reaction solution and the filtrate rotary evaporated at 7O0C leaving an oil (6.33 g), which crystallised on standing 60 hours. Recrystallisation from alcohol (7 ccs), gave minute white needles MP 11 5-11 80C (3.86 g, 63%).

C,7N23N203 requires: C 67.08, H 7.95, N 9.21% found: C 66.89, H 8.03, N 9.24%.

Example 13 I -(4-Ethylphenyl)-4-methyl-3-oxopyrazolidin-4ylmethyl pivalate Pivaloyl chloride (2.41 g, 0.02 M), and 1-(4-ethylphenyl)-4-hydroxymethyl-4-methylpyrazolidin- 3-one (4.69 g, 0.02 M), were refluxed in toluene (25 ccs) for 2+ hours till hydrogen chloride evolution ceased. On cooling a trace of solid was filtered off, and the filtrate rotary evaporated leaving an oil (6.95 g), which crystallized. Recrystallisation from alcohol (7 ccs), gave colourless transparent prisms MP 102-1040C (4.41 g, 69%), in three crops.

Cr8H26N203 requires: C 67.89, H 8.23, N 8.80% found: C 67.77, H 8.27, N 8.64%.

Example 14 4-Methyl-3-oxo-1 -(4-tolyl)pyrazolidin-4-ylmethyl 2,2-di methyl-4-Nmethyltrifluoracetamidobutyrate 4-Hydroxy-4-methyl-1-(4-tolyl)pyrazolidin-3-one (1.98 g, 0.009 M), and 4-(Nmethyltrifluoracetamido)-2,2-dimethylbutyryl chloride (2.34 g, 0.009 M), were refluxed overnight in toluene (12 ccs), when hydrogen chloride evolution had ceased. A little solid was filtered from the cooled solution which after rotary evaporation at 600C gave a viscous oil (4.1 g). This was chromatographed on a 'Florisil' column (350 g) eluting with 30% ethyl acetate in cyclohexane in 500 ccs fractions, and monitoring the fractions by thin layer chromatography on silica plates eluted with 50% ethyl acetate in cyclohexane. After eluting two minor components the desired product first appeared in fraction 4. The column eluant was changed to ethyl acetate when the bulk of product was eluted in fractions 5 and 6, giving a spot on the thin layer plate Rf 0.29. Further elution of

Examples 3, 4 and 6 do not fall within the invention but are included merely for comparison.

Compound 1 6 is the parent E.T.A. of Examples 12 and 14, and compound 1 7 is likewise the parent of Examples 13 and 15. Compounds 16, 17 and HMP are all included for comparative purposes.

Examples

Method of Use (1) Coating Procedure The electron transfer agent (ETA) was coated in single layer mordanted receivers of the following structure where the numbers

GEL (2000), MORDANT (2000), E.T.A. (150), BGE (100) Resin Coated Paper are in units of mg/m2. The E.T.A. was coated at a rate equal to the molar equivalent of 1 50 mg/m2 of 4 methyl-4-hydroxymethyl-1 -phenyl-3-pyrazolidinone. The coating stocks were adjusted to pH 5.5 with hydrochloric acid and deoxygenated with oxygen-free nitrogen. The solvent used for the E.T.A. was methanol where possible, otherwise cyclohexanone or ethyl acetate was used at a rate of 4% of the final coating stock. A weighed sample of E.T.A. was dissolved in the solvent (previously deoxygenated) and then dispersed in the coating melt (400C) by soniprobing for 2 minutes. The surfactant NG. was used at 12% to assist dispersion and coating. The mordant used was polyvinylimidazole partially quaternised (10%) with chloroethanol. BGE is 'Araldite' diluent and its active component is 1,4-butane diol-diglycidyl ether.

(2} Incubation After being allowed to dry down and harden (about 2 days) the coatings were cut into 1 inch strips and were exposed to an atmosphere of 1 200F and 75% RH for 3 days. (3 days was found on some earlier coatings to be roughly equal to 1 year on the shelf under ambient darkroom conditions.

This correlation is approximate and may vary with the E.T.A. used). NG.=nonylphenoxy (polyglycidol)IO.

(3) Processing (a) After incubation the coating strips were processed side by side with a control or unincubated coating on the same standard negative donor sheet. The donor sheet was of the following structure:

GEL (645) AgX (430) Mag.RDR (645) GEL (1000) Estar Support Mag.RDR is the magenta redox dye-releasing compound. Magenta RDR(c) described in U.K. Application 7,904,691. The donor was given a standard exposure through a step-wedge of 0.3 increments. The receiver and donor-sheets were laminated together by means of nip rollers after the donor had been soaked in processing activator for 8 seconds. Both functions were performed by means of a shallow tray processing machine. The laminate was left for 1 minute at room temperature (23 OC) and then peeled apart. The negative was fixed for 2 minutes in rapid-fix and washed for 5 minutes and dried. The receiver was washed for 5 minutes and dried. The processing solutions used had the compositions (1) and (2) shown below.

Processing Solution (1) Component Concentration Sodium Hydroxide 40 g/l Potassium Bromide 5 g/l 5-Methyl Benzotriazole 3.6 g/l The processed strips were measured for developed silver density using red light (status A) and for dye density using green light (status A).

Examples The silver and dye densities of a series of compounds coated and processed as described above are shown in Tables (1) and (2). The decrease in density of incubated samples indicates some loss of E.T.A. by oxidation. A stable E.T.A. is one which shows little density loss as compared with HMP. The results in Table (2) were for coatings with non-quaternized polyvinylimidazole and ESTAR support and are directly comparable with those in Table (1).

Table (1) Monopack Test Silver Densities Dye Densities Example Control In cuba ted Control Incubated HMP 0.255 0.09 1.92 0.28 (1) 0.160 0.170 0.64 0.60 (4) (2')* 0.190 0.175 1.16 1.21 (5) 0.245 0.235 1.70 0.70 (6) 0.130 0.04 0.84 0.16 (7) 0.170 0.110 1.02 0.45 (8) 0.245 0.22 0.96 0.85 (9) 0.270 0.210 1.25 0.85 (10) (2')* 0.130 0.140 1.01 1.13 (12) 0.290 0.200 0.60 0.58 (13) 0.170 0.130 0.49 0.39 (16) 0.300 0.185 1.75 0.19 (17) 0.340 0.09 1.49 0.51 Background Silver density=0.04 Background Dye density=0.15 *(2' means a 2 minute lamination as compared with the standard 1 minute lamination).

Table (2) Monopak Test Silver Densities Dye Densities Example Control Incubated Control Incubated HMP 0.32 0.13 0.82 0.20 (2) 0.19 0.11 0.35 0.15 (3) 0.24 0.11 0.57 0.11 Processing (b) Processing Solution (2) Component Concentration gll Potassium Hydroxide 33.6 5-Me-Benzotriazole 3.0 Potassium Bromide 2.0 11 Aminoundecanoic Acid 2.0 Multilayer coatings were soaked in solution (2) for 14 seconds at 82.50F and laminated with the receiver coatings (which contained the E.T.A.) for 5 minutes. The multilayer coatings had incorporated timing and acid release layers which adjusted the final pH of the laminate to about 5.0. After peeling apart the receiver was rinsed and air dried. The results for control and incubated samples are shown in Table (3).

Table (3) Multilayer Tests on Incubated Receivers Example Before Incubation After Incubation coated at Dmax Dmax equivalent molar levels B G R B G R HMP 2.52 2.41 2.41 0.69 0.56 0.56 (1) 2.16 2.20 2.10 2.18 2.19 1.82 (8) 2.26 2.29 2.16 1.94 1.93 1.42 (10) 2.00 1.62 1.66 1.98 1.58 1.61 (12) 2.03 1.81 1.85 2.11 1.85 1.46 It can be seen from the results in Tables (1) to (3) that many of the substituted E.T.A.'s are more stable to incubation than HMP although in the monopak tests they are also less active. In the multilayer results the activity of substituted E.T.A.'s is more comparable with HMP in the fresh state and very much superior to HMP after incubation.

Another set of mordanted receiver coatings were made and processed with a multilayer donor negative before and after incubation. The results are shown in Table (4).

Table (4) Multilayer Tests on Incubated Receivers Neutral Scale Densities (Status A) Before Incubation After Incubation Example B G R B G R HMP 2.34 2.41 2.46 0.67 0.39 0.33 (16) 2.22 2.27 2.42 0.26 0.17 0.15 (17) 2.24 2.34 2.45 0.24 0.16 0.15 (9)(EtOAc) 2.04 2.17 2.21 1.97 2.04 2.09 (9)(MeOH) 2.06 2.18 2.23 2.00 2.06 2.10 (1) 1.69 1.85 1.98 1.74 1.88 2.06 (8) 1.88 2.06 2.21 1.64 1.72 1.87 (12) 1.73 1.88 2.14 1.66 1.84 2.15 (13) 1.10 1.05 1.21 0.51 0.42 0.48 (14) 1.70 1.50 1.45 0.46 0.33 0.36 (15) 1.93 2.09 2.22 1.83 1.82 2.01 (11) 1.57 1.67 2.06 1.55 1.60 1.92 Many of the above Examples are more stable to incubation than HMP although several are also less active. Example (9) is the most active compound and is also very stable to incubation. Part of the decrease in dye densities obtained with Example (9) as compared with HMP is due to a slightly matt finish to the surface of the receiver coatings which results in a lower measured density.

Claims (14)

Claims

1. A compound of formula:

wherein R is a blocking group, wherein the group R.CO hydrolyses in alkaline aqueous solution and wherein R1 is H or alkyl.

2. A compound according to claim 1 wherein said blocking group possesses anchimeric assistance to hydrolysis.

3. A compound according to claim 1 wherein the group R is represented by formula (A), (B), (C) or (D) without the group C0X all as defined in U.K. Application 7934892 (2036994).

4. A compound according to claim 2 wherein R has the formula:

5. A compound according to any of claims 1 to 4 wherein R' is H, CH3 or C2H5.

6. A compound according to claim 1 and identified in any one of Examples 1, 2, 5 and 7 to 15.

7. A method of preparing a compound as defined in claim 1 wherein a compound of formula:

is reacted with a compound of formula R.CO.CI in an inert solvent at reflux in the absence of any base.

8. A method according to claim 7 in which the inert solvent is benzene or toluene.

9. A method according to claim 7 or 8 in which the reaction is continued until HCI ceases to be evolved.

1 0. A method according to claim 7 substantially as described in any one of the Examples 1 and 7 to 15.

11. A compound which has been produced by a method according to any of claims 7 to 9.

12. A compound which has been produced by a method according to claim 10.

1 3. A dye receiving element comprising a layer containing a mordant for a diffusible dye and a compound as defined in any one of claims 1 to 6, 11 and 12.

14. An element according to claim 1 3 substantially as herein described.