In German Patent Nr. 828,986, a process for the preparation of amidostyrylstilbene- disulphonic acid derivatives is described, which comprises reaction of diazotised 4-amino-4'- nitro-stilbene-2, 2'-disulphonic acid with cinnamic acids, reduction of the nitro-group and, finally, amidation of the resulting amine. This process is disadvantageous since, firstly substituted cinnamic acids are not readily available and, in particular, since the so-called Meerwein reaction of diazotised aromatic amines with unsaturated compounds results in, notoriously, poor yields.

Surprisingly, a novel process for the preparation of a wide variety of amidostyrylstilbene- disulphonic acid derivatives has now been found, which allows such compounds to be readily obtained in excellent yields.

Accordingly, in a first aspect, the invention provides a process for the preparation of a compound of formula in which X represents a group of the formula whereby, in formula (2), Ri is hydrogen, C-C4-alkyl which is unsubstituted or substituted by 1 to 3 halogen atoms, Ci-C4-alkyl-Ci-C4-alkoxy, phenyl which is unsubstituted or substituted by C1-C4-alkyl, nitro, halogen, S03M or COOM, amino, mono-C1-C4-alkylamino or phenylamino, whereby the phenyl group is unsubstituted or substituted by C1-C4-alkyl, nitro, halogen, S03M or COOM; in formula (3), R2 and R3 are hydrogen or together form a 6-membered unsaturated or saturated condensed ring, unbridged or bridged by 1 or 2 carbon atoms, the bond between these substituents being of single-or double-bond character; in formula (4), R4 represents hydrogen, C1-C4-alkyl, nitro, halogen, S03M or COOM; in formula (1), Y represents phenyl which is unsubstituted or substituted by Ci-C4-alkyl, nitro, halogen, S03M or COOM or represents a heteroaromatic residue and, in any of the above formulae, M represents hydrogen, an alkaline-or alkaline earth-metal cation, or a cation formed from an amine, characterized by the following reaction sequence: a) Treatment of 4-amino 4'-nitrostilbene-2, 2'-disulphonic acid or salts thereof with an acylating agent resulting in the introduction of the group X; b) reduction of the nitro group to an amino group; c) diazotisation of the resulting aminostilbene compound and d) subsequently reacting the resulting diazonium salt with a compound of formula Y-CH=CH2 (9) in a solvent and in the presence of a palladium catalyst and an inorganic salt, resulting in the introduction of the group Y, X and Y being as previously defined.

Step a) of the above reaction sequence is carried out in a suitable. solvent ter, in the presence of a base such as an alkaline or alkaline earth metal salt such as Li-, K-, Na-, Ca-, or Mg-acetate, bicarbonate, carbonate, hydroxide etc., sodium carbonate being particularly suitable. As acylating agent, appropriate derivatives of the corresponding mono- or dibasic carboxylic acids, such as anhydrides or halogenides, particularly acid chlorides, may be employed. Examples of such acylating agents are acetic or propionic anhydride, acetyl or propionyl chloride, optionally substituted benzoic acid anhydrides or benzoyl chlorides, mono-, di-or trichlor or fluoro acetic anhydrides or acetyl chlorides, optionally substituted phthalic anhydrides, succinic anhydride or optionally substituted benzene sulphonyl halides, particularly chlorides, such as benzene sulphonyl chloride or p-toluene sulphonyl chloride For the reduction step b), any suitable process for the reduction of an aromatic nitro- compound to the corresponding aromatic amine is suitable as described, for example, in Houben and Weyl, providing further reduction of either the olefinic double bond or the aromatic rings does not occur. Particularly suitable, in this case, is reduction by metals such as iron or tin in the presence of mineral acids such as hydrochloric or acetic acid, the so- called Bèchamp Reduction with iron and acetic acid being most preferred.

The diazotisation step c) of the process is carried out in the presence of a strong mineral acid and a diazotising reagent. Suitable strong mineral acids are, for example, hydrochloric acid, sulphuric acid, methane sulphonic acid or tetrafluoroboric acid, sulphuric acid being particularly preferred, whilst suitable diazotising reagents are, for example, sodium nitrite, Ci-C5-alkyl nitrites or nitrosyl sulphuric acid, sodium nitrite being especially suitable. The temperature at which the diazotisation reaction is carried out is dependent on the amine of formula (2), but, in general, lies within the range of between-10 and 30°C,-5 to 25°C or 0 to 25°C being preferred.

The palladium (II) compound used as a catalyst in step d) of the process is PdCts, PdBr2, Pd (NO3) 2, H2PdC14, Pd (OOCCH3) 2, [PdCI4] Na2, [PdC14] Li2, [PdC14] K2, palladium (II) acetylacetonate, palladium (II) dibenzylideneacetone (dba) or solvates thereof, <BR> <BR> <BR> dichloro- (1, 5-cyclooctadiene) palladium (lI), dichlorobis- (acetonitrile) palladium (II), dichlorobis- (benzonitrile) palladium (ll), 7C-allylpalladium (ll) chloride dimer, bis- (-methallyl palladium (II) chloride) or -allylpalladium (II) acetylacetonate, PdCl2, Pd (dba Pd (OCOCH3) 2. or PdC12 being preferred.

The quantity of palladium catalyst used is in an amount of 0.01 to 5 mole %, based on the diazonium salt, preferrably 0.1 to 1%.

Step d) of the process may be effected in water as solvent or may be conducted in a two- phase solvent system comprising water and a water-immiscible organic solvent such as halogenated hydrocarbons in the presence of a phase transfer catalyst. Alternatively, an organic solvent may be empioyed, whereby the organic solvent is one or more of an alcohol ; ketone; carboxylic acid; sulfone ; sulfoxide ; N, N-tetrasubstituted urea; N-alkylated lactam or N-dialkylated acid amide; ether; aliphatic carboxylic acid ester or lactone ; nitrile ; and a glyme.

The inorganic salt used in step d) of the process is a Li-, Na-, K-, NH4-, Mg-or Ca--salt of a carboxylic acid, preferably lithium-, potassium-or sodium acetate, bicarbonate or carbonate, whereby sodium or potassium acetate, or sodium or potassium bicarbonate are especially suitable, the inorganic salt being used in excess.

The reaction step d) of the process is carried out at a temperature of between 10 and 100°C, preferably at between 10 and 80°C and most preferably at between 20 and 70°C, In a second aspect of the invention, there is provided a process for the preparation of the compound of formula (1) characterized by the following reaction sequence: a) treatment of 4-amino 4'-nitrostilbene-2, 2'-disulphonic acid or salts thereof with an acetylating agent; b) reduction of the nitro group to an amino group; c) diazotisation of the resulting aminostilbene compound; d) subsequently reacting the resulting diazonium salt with a compound of formula Y-CH=CH2 (9) in a solvent and in the presence of a palladium catalyst and an inorganic salt, resulting in the introduction of the group Y, e) hydrolysis of the acetyl group and, finally, f) treatment of the resulting amino compound with an acylating agent resulting in the introduction of the group X, X and Y being as previously defined.

Step a) of the above reaction sequence is carried out in a suitable solvent such as water, in the presence of a base such as an alkaline or alkaline earth metal salt such as Li-, K-, Na-, Ca-, or Mg-acetate, bicarbonate, carbonate, hydroxide etc., sodium carbonate being particularly suitable. As acetylating agent, acetic anhydride or acetyl chloride, preferably the former may be used.

Steps b), c) and d) of this reaction sequence are carried out as described above for the prior reaction sequence, whilst the hydrolysis step e) is preferably carried out in aqueous medium in the presence of an inorganic base. As inorganic base, hydroxides of Li, K, or, especially, Na may be used. Alternatively, hydrolysis may be performed in the presence of strong mineral acid such as hydrochloric or sulphuric acid.

The final step f) of the reaction sequence is preferably carried out in a dipolar aprotic solvent such as dimethylsulphoxide, dimethylacetamide, N-methylpyrrolidone or, more preferably, dimethylformamide or, alternatively, in glacial acetic acid. As acylating agents optionally substituted phthalic anhydrides, succinic or maleic anhydrides, bicyclo (2,2,1)-5-heptene-2,3- dicarboxylic acid anhydride or optionally substituted benzoyl chlorides may be employed, whereby, in the latter case, reaction is preferably performed in water and in the presence of an inorganic base.

Either of these variations of the process of the invention are particularly suitable for the preparation of a compound of formula (1), whereby X represents a group of formula (2), in which R1 is hydrogen, C1-C4-alkyl which is unsubstituted or substituted by 1 to 3 halogen atoms, C1-C4-alkyl-C1-C4-alkoxy, phenyl which is unsubstituted or substituted by Ci-C4-alkyl, nitro, halogen, SO3M or COOM, amino, mono-Ct-C4-alkylamino or phenylamino, whereby the phenyl group is unsubstituted or substituted by C1-C4-alkyl, nitro, halogen, S03M or COOM and Y and M are as defined previously and, more especially, for the preparation of a compound of formula (1), in which R1 represents hydrogen, C1-C4-alkyl, CC13, CHC12, CH2CI, CF3, CHF2, CH2F or phenyl which is unsubstituted or substituted by C1-C4-alkyl, nitro, chloro, SO3M or COOM ; Y represents phenyl which is unsubstituted or substitutea''- Ikyl, chloro, SO3M or COOM, preferably unsubstituted phenyl, or pyridyl and M) usly defined.

Furthermore, either of the above variations of the process are particularly suitable for the preparation of a compound of formula (1), whereby X represents a group of formula R4, Y and M being as defined previously and, more especially, for the preparation of a compound of formula (1), in which R4 represents hydrogen and Y represents phenyl which is unsubstituted or substituted by C1-C4-alkyl, chloro, SO3M or COOM, preferably unsubstituted phenyl, or pyridyl.

In addition, either of the above variations of the process are particularly suitable for the preparation of a compound of formula (1), whereby X represents a group of formula (4), in which R4 is hydrogen, C1-C4-alkyl, nitro, halogen, S03M or COOM, preferably hydrogen or methyl, and Y and M are as defined previously and, more especially, for the preparation of the compound in which Y represents phenyl which is unsubstituted or substituted by Ci-C4- alkyl, chloro, S03M or COOM, preferably unsubstituted phenyl, or pyridyl.

In any of the preceding compounds, M is preferably hydrogen, Li, Na, K, Ca, Mg, ammonium, quaternary ammonium with Cl-Ca-alkyl groups, primary, secondary or tertiary ammonium with Ci-C8-alkyl groups or mono-, di-or triethanolamino, more preferably, hydrogen, Na or K.

As previously mentioned, some of the compounds prepared according to the process of the invention are novel.

Consequently, a further aspect of the invention is a compound of formula in which X represents a group of the formula whereby, in formula (3), R2 and R3 are hydrogen or together form a 6-membered unsaturated or saturated condensed ring, unbridged or bridged by 1 or 2 carbon atoms, the bond between these substituents being of single-or double-bond character; in formula (4), R4 represents hydrogen, C1-C4-alkyl, nitro, halogen, SO3M or COOM ; in formula (1 a), Y represents phenyl which is unsubstituted or substituted by Ci-C4-alkyl, nitro, halogen, SO3M or COOM or represents a heteroaromatic residue and, in any of the above formulae, M represents hydrogen, an alkaline-or alkaline earth-metal cation, or a cation formed from an amine.

Preferred compounds of formula (1a) are those in which X represents a group of formula R4, Y and M being as previously defined, in particular, those in which R4 represents hydrogen, Y represents phenyl which is unsubstituted or substituted by C1-C4-alkyl, chl ^ M or COOM, more preferably, unsubstituted phenyl, or pyridyl and M is as previously defined.

A further group of preferred compounds are those of the above formula (1 a), whereby X represents a group of formula (4), in which R4 is hydrogen, Ci-C4-alkyl, nitro, halogen, S03M or COOM, preferably hydrogen or methyl, and Y and M are as defined previously, especially those in which Y represents phenyl which is unsubstituted or substituted by C1-C4-alkyl, chloro, SO3M or COOM, most especially, unsubstituted phenyl, or pyridyl and M is as previously defined.

In any of the above compounds of formula (la), M is preferably hydrogen, Li, Na, K, Ca, Mg, ammonium, quaternary ammonium with C1-C8- alkyl groups, primary, secondary or tertiary ammonium with C1-C8-alkyl groups or mono-, di- or triethanolamino, especially hydrogen, Na or K.

In dissolved or finely divided states, the compounds of formula (1 a) display a more or less pronounced fluorescence. They are therefore used, according to the invention, for optically brightening synthetic or natural organic materials.

Examples of such materials which may be mentioned, without the review given below being intended to express any limitation thereto, are textile fibres from the following groups of organic materials, insofar as optical brightening thereof enters into consideration: (a) Polyamides which are obtainable as polymerisation products by ring opening, for example those of the polycaprolactam type, (b) polyamides which are obtainable as polycondensation products based on bifunctional or polyfunctional compounds capable of undergoing a condensation reaction, such as hexamethylenediamine adipate and (c) natural textile organic materials of animal or vegetable origin, for example based on cellulose or proteins, such as cotton or wool, linen or silk.

The organic materials to be optically brightened can be in diverse stages of processing and are preferably finished textile products. They can, for example be in the fc goods, textile filaments, yarns, twisted yarns, nonwovens, felts, textile fabrics, text tes or knitted fabrics.

The brighteners defined above are of particular importance for the treatment of textile fabrics. The treatment of textile substrates is advantageously carried out in an aqueous medium in which the particular optical brighteners are present in a finely divided form (suspensions, so-called microdispersions and in some cases solutions). Dispersing agents, stabilisers, wetting agents and further auxiliaries can optionally be added during the treatment.

The treatment is usually carried out at temperatures of from about 20° to 140°C, for example at the boiling point of the bath, or in the region thereof (about 90°C). For the finishing, according to the invention, of textile substrates it is also possible to use solutions or emulsions in organic solvents, as are used in dyeing practice in so-called solvent dyeing (pad-thermofix method and the exhaustion dyeing process in dyeing machines).

The optical brighteners which can be used according to the present invention can also be employed, for example, in the following use forms: (a) In mixtures with so-called"carriers", wetting agents, softeners, swelling agents, antioxidants, light stabilisers, heat stabilisers and chemical bleaching agents (chlorite bleach and bleaching bath additives).

(b) In mixtures with crosslinking agents and finishing agents (for example starch or synthetic finishing agents) and also in combination with very diverse textile finishing processes, especially synthetic resin finishes (for example crease resistant finishes such as"wash-and- wear","permanent press"and"no-iron"), and also flame resistant finishes, soft handle finishes, anti-soiling finshes or anti-static finishes or antimicrobial finishes.

(c) As additives to various soaps and washing agents.

(d) In combination with other substances having an optical brightening action.

If the brightening process is combined with textile treatment or finishing methods, the combined treatment can in many cases advantageously be effected with the aid of corresponding stable formulations which contain the compounds having an optical brightening action in a concentration such that the desired brightening effect is obtained.

In certain cases, the full effect of the brightener is achieved by an after-tre liS can be, for example, a chemical treatment (for example acid treatment), a thermal treatment (for example heat) or a combined chemical/heat treatment.

The amount of the optical brighteners to be used according to the invention, relative to the material to be optically brightened, can vary within wide limits. A distinct and durable effect can already be achieved with vary small amounts and in certain cases, for example, with amounts of 0.03% by weight. However amounts of up to about 0.5% by weight can also be used. For most cases of interest in practice, amounts of between 0.05 and 0.5% by weight relative to the material to be brightened, are preferably of interest.

The optical brighteners are also especially suitable as additives for washing baths or to industrial and household washing agents and they can be added in various ways. They are appropriately added to washing baths in the form of their solutions in water or organic solvents or also in a state of fine division as aqueous dispersions or slurries. They, or their components, are advantageously added to household or industrial washing agents at any phase of the manufacturing process of the washing agent, for example to the so-called "slurry"prior to spray-drying of the washing powder or during the preparation of liquid washing agent combinations. The compounds can be added both in the form of a solution or dispersion in water or other solvents and also without auxiliaries in the form of a dry brightener powder. However, they can also be sprayed, in the dissolved or pre-dispersed form, onto the finished washing agent.

Washing agents which can be used are the known mixtures of detergent substances, such as, for example, soap in the form of chips and powders, synthetic products, soluble salts of sulphonic acid half-esters of higher fatty alcohols, arylsulphonic acids, which are substituted by higher alkyl and/or polysubstituted by alkyl, carboxylic acid esters with alcohols of medium to higher molecular weight, fatty acid acylaminoalkyl-or aminoaryl-glycerol- sulphonates, phosphoric acid esters of fatty alcohols and the like. So-called"builders"which can be used are, for example, alkali metal polyphosphates and alkali metal polymeta- phosphates, alkali metal pyrophosphates, alkali metal salts of carboxyethylcellulose and other"soil redeposition inhibitors", and also alkali metal silicates, alkali metal carbonates, alkali metal borates, alkali metal perborates, nitrilotriacetic acid, ethylenediamine-tetraacetic acid and foam stabilisers, such as alkanolamides of higher fatty acids. Fu'-Lh he washing agents can contain, for example: antistatic agents, superfatting sl n agents, such as lanolin, enzymes, antimicrobial agents, perfumes and dyestuffs.

The brighteners have the particular advantage that they are also effective in the presence of active chlorine donors, such as, for example, hypochlorite and can be used without substantial loss of the effects in washing baths with non-ionic washing agents, for example alkylphenol polyglycol ethers. Also in the presence of perborate or peracids and activators, for example tetraacetylglycoluril or ethylenediamine-tetraacetic acid are the new brighteners very stable both in pulverulent washing agent and in washing baths.

The brighteners according to the invention are added in amounts of 0.005 to 2% or more and preferably of 0.03 to 0.5%, relative to the weight of the liquid or pulverulent ready-to-use washing agent. When they are used to wash textiles made of cellulose fibres, polyamide fibres, cellulose fibres with a high grade finish, wool and the like, wash liquors which contain the indicated amounts of the optical brighteners according to the invention impart a brilliant appearance in daylight.

The washing treatment is carried out, for example, as follows : The indicated textiles are treated for 1 to 30 minutes at 5° to 100°C and preferably at 25° to 100°C in a wash bath which contains 1 to 10 g/kg of a composite washing agent containing builders and 0.05 to 1% relative to the weight of the washing agent, of the brighteners claimed. The liquor ratio can be 1 : 3 to 1: 50. After washing, the textiles are rinsed and dried in the customary manner. The wash bath can contain, as a bleach additive, 0.2 g/l of active chlorine (for example in the form of hypochlorite) or 0.1 to 2 g/l of sodium perborate.

The brighteners according to the invention can also be applied from a rinsing bath with a "carrier". For this purpose the brightener is incorporated in a soft rinsing agent or in another rinsing agent, which contains, as the"carrier", for example, polyvinyl alcohol, starch, copolymers on an acrylic basis or formaldehyde/urea or ethylene-urea or propylene-urea derivatives, in amounts of 0.005 to 5% or more and preferably of 0.2 to 2%, relative to the rinsing agent. When used in amounts of 1 to 100 ml, and preferably of 2 to 25 ml, per litre of rinsing bath, rinsing agents of this type, which contain the brighteners according to the invention, impart brilliant brightening effects to very diverse types of treated textiles.

A further application of the compounds of the invention is for the brightenit either in the pulp mass during paper manufacture or in the size-press, which has been described in British Patent Specification 1,247,934, or preferably in coating compositions. When brighteners of the present invention are employed in such formulations papers brightened with them exhibit a very high degree of whiteness.

The compounds obtained by the process of the present invention are particularly advantageous in that they exhibit not only extremely high whitening ability, but, in addition, in many cases highly desirable water solubilities and also possess excellent white aspects in the solid state.

The following Examples serve to illustrate the invention; parts and percentages are by weight, unless otherwise stated.

Example 1 Step a) In 100 ml of water, 41 g of the mono-sodium salt of 4-amino-4'-nitrostilbene disulphonic acid are slurried to an orange-brown suspension of pH 2.1.50 g of sodium carbonate are then added slowly to the suspension with stirring, foaming being kept under control. 10.6 g of acetic anhydride are then added dropwise over 20 minutes with stirring, whereby the temperature rises to 28°C and the pH drops to 3.8-4.0. After stirring for a further 1 hour, approximately 200 ml of a yellowish-brown suspension of the acetylated compound are obtained which are used directly for the next step.

Step b) 24 g of iron filings are stirred into 40 ml of water and heated to 80°C. In order to etch the iron, 0.5 mi of 80% acetic acid are added and the mixture stirred for 15 minutes. The temperature is then raised to 100°C and the suspension from the previous step a) added.

The redox potential rises from an initial 145 mV to 160 mV. Following the addition of the total educt, the mixture is stirred for a further 10 minutes, cooled to 60°C and the pH adjusted to 8-8.5 by addition of 4.5 g of 50% sodium hydroxide solution. The mixture is then clarified over a pre-heated suction filter and washed with a small amount of water. There are obtained approximately 280 mi of a brownish solution having a nitrite valuE''mately 15%, the solution being used directly for the next step.

Step c) 20 g of concentrated sulphuric acid are stirred into a mixture of 20 g of water and 150 g of ice and the solution obtained in step b) above, to which 20.2 g of 37% sodium nitrite solution were previously mixed, added gradually over 90 minutes with stirring, the temperature being maintained below 15°C by external cooling. After stirring for a further 1 hour below 15°C, the nitrite excess is checked and, if necessary, destroyed by the addition of a little sulphamic acid. The suspension is immediately filtered with suction to yield approximately 100 g of reddish filter-cake which is washed with 50 ml of water.

Step d) The approximately 100 g of filter-cake obtained in step c) are slurried in 200 g of glacial acetic acid and cooled to 15°C. Then, 300 g of acetic anhydride are gradually added dropwise over 2 hours with stirring. 29 g of sodium bicarbonate are then added in portions, care being taken to avoid excess foaming. Then, 0.2 g of Pd (dba) 2 and 14 g of styrene are added to the mixture. Gas evolution from the reddish-brown suspension commences immediately and the temperature rises. Gas evolution continues for 1 to 2 hours, the temperature being maintained at 40°C. Consumption of the diazonium salt is followed by testing with an alkaline H-acid solution, whereby no violet colouration is observed when reaction is complete. The yellowish suspension is cooled, the product separated by suction filtration, washed with glacial acetic acid, dried and finally purified by recrystallisation from water/salt. After drying, there are obtained 32 g of the compound of formula (101), characterised by the following'H-NMR spectral data, recorded in deutero- dimethylsulphoxide : 2.1 3H, s amide methyl group 7.26 1 H, t, J=8 Hz aromatic H 7.26 2H, q, J=17 Hz vinyl H's (overlapping) 7.35 2H, t, J=8 Hz aromatic H's 7.60 5H, m aromatic H's (overlapping) 7.70 1 H, d, J=8 Hz aromatic H 7.97 1 H, s aromatic H adjacent to sulphonic acid group 8.03 1 H, s aromatic H adjacent to sulphonic acid group 8.08 2H, q, J=17 Hz vinyl H's between sulphonic acid groups 10.9 1H, s N-H Example 2 Step a) In 100 mi of water, 41 g of the mono-sodium salt of 4-amino-4'-nitrostilbene disulphonic acid are slurried to an orange-brown suspension of pH 2.1. The pH of the suspension is then adjusted to 7-8 by the slow addition of 50 g of sodium carbonate, with stirring, foaming being kept under control. 20.6 g of toluene-p-sulphonyl chloride are then added gradually over 20 minutes, with stirring, at room temperature. The temperature rises to 28°C and the pH is maintained at 7-8 by dropwise addition of sodium hydroxide solution. After stirring for a further 1 hour, approximately 200 ml of a yellowish-brown suspension of the tosylated compound are obtained which are used directly for the next step.

Step b) 24 g of iron filings are stirred into 40 ml of water and heated to 80°C. In order to etch the iron, 0.5 ml of 80% acetic acid are added and the mixture stirred for 15 minutes. The temperature is then raised to 100°C and the suspension from the previous step a) added.

The redox potential rises from an'initial 145 mV to 160 mV. Following the addition of the total educt, the mixture is stirred for a further 10 minutes, cooled to 60°C and the pH adjusted to 8-8.5 by addition of 4.5 g of 50% sodium hydroxide solution. The mixture is thQr rrified over a pre-heated suction filter and washed with a small amount of water. obtained approximately 280 ml of a brownish solution having a nitrite value of approximately 15%, the solution being used directly for the next step.

Step c) 20 g of concentrated sulphuric acid are stirred into a mixture of 20 g of water and 150 g of ice and the solution obtained in step b) above, to which 20.2 g of 37% sodium nitrite solution were previously mixed, added gradually over 90 minutes with stirring, the temperature being maintained below 15°C by external cooling. After stirring for a further 1 hour below 15°C, the nitrite excess is checked and, if necessary, destroyed by the addition of a little sulphamic acid. The suspension is immediately filtered with suction to yield approximately 100 g of reddish filter-cake which is washed with 50 mi of water.

Step d) The approximately 100 g of filter-cake obtained in step c) are slurried in 200 g of glacial acetic acid and cooled to 15°C. Then, 300 g of acetic anhydride are gradually added dropwise over 2 hours with stirring. 29 g of sodium bicarbonate are then added in portions, care being taken to avoid excess foaming. Then, 0.2 g of Pd (dba) 2 and 14 g of styrene are added to the mixture. Gas evolution from the reddish-brown suspension commences immediately and the temperature rises. Gas evolution continues for 1 to 2 hours, the temperature being maintained at 40°C. Consumption of the diazonium salt is followed by testing with an alkaline H-acid solution, whereby no violet colouration is observed when reaction is complete. The yellowish suspension is cooled, the product separated by suction filtration, washed with glacial acetic acid, dried and finally purified by recrystallisation from water/salt. After drying, there are obtained 42 g of the compound of formula (102), characterised by the following'H-NMR spectral data, recorded in deutero- dimethylsulphoxide : 2.32 3H, s methyl group 7.06 1 H, d, J=8 Hz aromatic H 7.10 2H, q, J=17 Hz vinyl H's (overlapping) 7.28 3H, t, J=8 Hz aromatic H's 7.32 3H, m aromatic H's (overlapping) 7.52 1 H, s aromatic H adjacent to sulphonic acid group 7.60 6H, m aromatic H's (overlapping) 8. 00 2H, q, J=17 Hz vinyl H's between sulphonic acid groups 8.10 1 H, s aromatic H adjacent to sulphonic acid group 10.9 1H, s N-H Example 3 By substituting the 10.6 g of acetic anhydride for 15.4 g of benzoyl chloride in step a) of example 1 and otherwise proceeding in an identical manner in steps b), c) and d), there are obtained 35 g of the compound of formula (103), characterised by the following'H-NMR spectral data, recorded in deutero-dimethylsulphoxide : 7.35 1 H, t, J=8 Hz aromatic H 7.35 2H, q, J=16 Hz vinyl H's (overlapping) 7.45 2H, t, J=8 Hz aromatic H's 7.62 3H, m aromatic H's (overlapping) 7.75 4H, m aromatic H's (overlapping) 7.96 2H, d aromatic H's 8.07 1 H, s aromatic H 8.10 2H, d, J=4 Hz aromatic H 8.18 2H, q, J=16 Hz vinyl H's between sulphonic acid groups 8.30 1 H, s aromatic 10.431H, s N-H Example 4 Step e) The crude product obtained in steps a) to d) of Example 1, either moist or dried, is slurried in 250 mi of 20% sodium hydroxide solution and heated to 120°C with stirring. The mixture is stirred for 3 hours at this temperature, cooled to 60°C, the pH adjusted to 7 by addition of 60% sulphuric acid and, finally, filtered. There are obtained approximately 90 g of a yellowish-green filter-cake which, after drying, yields 36 g of the intermediate 4-amino-4'- styryl-stilbene-2, 2'-disulphonic acid salt with an active content of 90%.

Step f) The product obtained in step e) above is slurried in 150 ml of dimethylformamide, mixed with 10 g of phthalic anhydride and heated to 140°C with stirring. After stirring for 4 hours at this temperature, the solvent is removed on a rotary evaporator and the residue recrystallised from 5% aqueous sodium chloride. There are obtained 40 g of the compound of formula (104), characterised by the following 1H-NMR spectral data, recorded in deutero- dimethylsulphoxide : 7.30 1 H, t, J=8 Hz aromatic H 7.30 2H, q, J=16 Hz vinyl H's (overlapping) 7.40 2H, t, J=8 Hz aromatic H's 7.48 1 H, d, J=8 Hz aromatic H 7.48 4H, m aromatic H's (overlapping) 7.85 1 H, d, J=8 Hz aromatic H 7.95 5H, m aromatic H's (overlapping) 8.03 1 H, s aromatic H adjacent to sulphonic acid group 8.22 2H, q, J=16 Hz vinyl H's between sulphonic acid groups Example 5 Step f) 36 g of the hydrolysis product, 4-amino-4'-styryl-stilbene-2, 2'-disulphonic acid salt with an active content of 90%, obtained in step e) of Example 4 are slurried in 250 ml of glacial acetic acid, 12 g of bicyclo (2,2,1)-5-heptene-2,3-dicarboxylic acid anhydride added and the mixture heated to 118°C. After being allowed to react for 3 hours at this temperature, the product is separated by filtration and dried. There are obtained 42 g of the compound of formula (105), characterised by the following'H-NMR spectral data, recorded in deutero- dimethylsulphoxide : 1.16 2H, s aliphatic H's 2.10 1 H, s aliphatic H 3.50 2H, s aliphatic H's a to amide 6.30 2H, s vinyl H's in bicyclic ring system 7.10 1 H, t, J=8 Hz aromatic H 7.28 1 H, t, J=8 Hz aromatic H 7.28 2H, q, J=16 Hz vinyl H's (overlapping) 7.40 2H, t, J=8 Hz aromatic H's 7.65 1 H, s aromatic H adjacent to sulphonic acid group 7.75 5H, m aromatic H's (overlapping) 8.03 1 H, s aromatic H adjacent to sulphonic acid group 8.15 2H, q, J=16 Hz vinyl H's between sulphonic acid groups Example 6 Step f) 36 g of the hydrolysis product, 4-amino-4'-styryl-stilbene-2, 2'-disulphonic acid salt with an active content of 90%, obtained in step e) of Example 4 are slurried in 200 ml of water, whereby an orange-brown suspension of pH 7-8 results. If necessary, the pH is adjusted to 7-8 by the slow addition of sodium carbonate to the stirred suspension, care being taken to avoid foaming. After warming to 50°C, 14.4 g of 4-nitrobenzoyl chloride are added gradually over 1 hour at this temperature, the pH being maintained at 7-8 by addition of sodium hydroxide solution. The mixture is stirred for a further 3 hours, approximately 250 ml of a yellowish-orange suspension being obtained which is salted out by addition of 16 g of sodium chloride, cooled to room temperature, separated by filtration and the resulting filter- cake dried. There are obtained 36 g of the compound of formula (106), characterised by the following'H-NMR spectral data, recorded in deutero-dimethylsulphoxide : 7.25 1 H, t, J=8 Hz aromatic H 7.25 2H, q, J=16 Hz vinyl H's (overlapping) 7.35 2H, t, J=8 Hz aromatic H's 7.68 5H, m aromatic H's (overlapping) 7.92 1H, d, J=8 Hz aromatic H 8.05 1 H, s aromatic H adjacent to sulphonic acid group 8.12 2H, q, J=16 Hz vinyl H's between sulphonic acid groups 8.28 1 H, s aromatic H adjacent to sulphonic acid group 8.28 2H, d, J=8 Hz aromatic H's adjacent to sulphonic acid group 8.35 2H, d, J=8 Hz aromatic H's adjacent to sulphonic acid group 10.82 1H, s N-H Example 7 Step f) 36 g of the hydrolysis product, 4-amino-4'-styryl-stilbene-2, 2'-disulphonic acid salt with an active content of 90%, obtained in step e) of Example 4 are slurried in 250 ml of glacial acetic acid, 10 g of phthalic anhydride added and the mixture heated to 118°C. After being allowed to react for 3 hours at this temperature, the product is separated by filtration and dried. There are obtained 42 g of the compound of formula (107), characterised by the following'H-NMR spectral data, recorded in deutero-dimethylsulphoxide : 7.22 1 H, t, J=8 Hz aromatic H 7.22 2H, q, J=16 Hz vinyl H's (overlapping) 7.38 2H, t, J=8 Hz aromatic H's 7.58 2H, t, J=8 Hz aromatic H's 7.62 5H, m aromatic H's (overlapping) 7.74 1 H, t, J=8 Hz aromatic H 7.86 1 H, d, J=8 Hz aromatic H 8.03 1 H, s aromatic H adjacent to sulphonic acid group 8.12 2H, q, J=16 Hz vinyl H's between sulphonic acid groups 8.18 1 H, s aromatic H adjacent to sulphonic acid group 10.45 1H, s N-H Example 8 Step f) 36 g of the hydrolysis product, 4-amino-4'-styryl-stilbene-2, 2'-disulphonic acid salt with an active content of 90%, obtained in step e) of Example 4 are slurried in 250 ml of dimethylformamide, 6 g of succinic anhydride added and the mixture heats After being allowed to react for 3 hours at this temperature, the product is separ ation and dried. There are obtained 40 g of the compound of formula (108), characterised by the following'H-NMR spectral data, recorded in deutero-dimethylsulphoxide : 2.40 4H, s cycloaliphatic H's 7.25 1 H, t, J=8 Hz aromatic H 7.25 2H, q, J=16 Hz vinyl H's (overlapping) 7.38 2H, t, J=8 Hz aromatic H's 7.58 2H, t, J=8 Hz aromatic H's 7.60 4H, m aromatic H's (overlapping) 7.70 2H, d, J=8 Hz aromatic H's 8.00 1 H, s aromatic H 8.03 1 H, s aromatic H adjacent to sulphonic acid group 8.07 2H, q, J=16 Hz aromatic H's between sulphonic acid groups ApplicationExamples A wood-free base paper containing neither optical brightener nor dyestuff and having a brightness of 83.8 is used as test substrate.

To a coating colour containing 60 parts of calcium carbonate and 40 parts of kaolin are added 9 parts of SBR-latex and 0.25 parts of a polymeric acrylic acid. Additionally, in Examples 9,10 and 11, 1 part of polyvinyl alcohol is added, whilst in Example 12,1 part of carboxymethyl cellulose is added. The pH of the coating colour is then adjusted to 9.0 with sodium hydroxide solution and 0.2 parts of the appropriate compound are stirred in. With the aid of a laboratory hand-coater, sufficient coating is applied in order that, after drying and climatizing, a coat weight of 12 g/m2 results.

Whiteness and fluorescence according to CIE and ISO, respectively, are then measured.

The results are shown in the following Table 1: Table 1 Example Nr. Compound Nr. Whiteness Fluorescence None 70. 3 0. 0 9 (101) 90. 4 6. 9 10 (102 85. 8 11 (105) 87. 7 12 (108) 89. 7 6. 9