ITMI982175A1 - PHOTOCROMATIC COMPOUNDS, PROCEDURE FOR THEIR PREPARATION AND THEIR USE IN POLYMERIC MATERIALS. - Google Patents

Description

"PHOTOCROMATIC COMPOUNDS, PROCEDURE FOR THEIR PREPARATION AND THEIR USE IN POLYMER MATERIALS"

DESCRIPTION

The present invention relates to photochromic compounds.

More particularly, the present invention relates to silylated photochromatic compounds, a process for their preparation and their use in polymeric materials.

A further object of the present invention are the polymeric compositions containing said photochromic compounds and the photochromatic articles obtained from their processing.

Photochromic compounds are substances that have the characteristic of reversibly changing color and / or degree of light transmission when exposed to sunlight or artificial light in the band that goes from UV to visible, or to some types of electromagnetic radiation, returning to their state of original color and transmission when the initial light source is removed.

Substances endowed with photochromic characteristics are numerous and belong to different classes of both organic and inorganic compounds such as, for example, those described in the texts "Photochromism", by G. H. Brown (Ed.), Vol. Ili of the Weissberger series "Techniques of Organic Chemistry ", Wiley Interscience, New York (1971) and in" Photochromism: Molecules and Systems ", by H. Diirr and H. Bouas-Laurent (Ed.), Vol. 40 of the series" Studies in Organic Chemistry ", Elsevier ( 1990).

Among the organic photochromatic compounds, particularly known and used, are those belonging to the classes of spiro-indolino-oxazines, spiro-pyranes and chromenes.

The above compounds are capable of imparting photochromic characteristics to polymerized organic materials used, for example, in the manufacture of photochromic lenses for spectacles, special inks, toys, and in many other applications.

By way of example we can cite the US patents 3,562,172, USA 3,578,602, USA 4,215,010, USA 4,342,668, USA 5,055,576, USA 5,110,922, USA 5,186,867, EP 146,135, EP 134,633, EP 141,407, EP 245,020, IT 1,233,348 and IT 1,238,694.

The Applicant has now found new silylated photochromic compounds which have good photochromic characteristics, good fatigue resistance and good colorability characteristics.

Therefore, the object of the present invention is photochromic compounds having general formula (I):

in which:

X represents an oxygen atom; an atom of sulfur; an atom of selenium; an NH group; or an NRa group wherein Ra represents a linear or branched C1-C10 alkyl group; a benzyl group, called benzyl group optionally substituted, with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X <f>) 3 groups in which X 'is selected from fluorine, chlorine and bromine, groups hydroxyl groups, linear or branched C1-C10 alkyl groups, linear or branched C1-C6 alkoxyl groups, carboxyl groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group;

R'1 represents a linear or branched C1-C10 alkyl group, said alkyl group optionally substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C {X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2, 2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amino groups, N, N-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2, 2, 6, 6-tetramethylpiperidine group;

R'2 represents a hydrogen atom; an OH group; or a photochromic compound having general formula (II):

R 'represents a linear or branched C1-C10 alkyl group; a linear or branched C2-C10 acyl group; a linear or branched C2-C10 heteroalkyl group in which the heteroatom is selected from nitrogen, oxygen, sulfur and selenium; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group;

R '' represents a hydrogen atom; a halogen atom selected from fluorine, chlorine and bromine; a linear or branched C1-C6 alkyl group; a linear or branched C1-C6 alkoxy group; a phenyl group; a phenoxy group;

P 'represents one of the following groups having general formula (III), (IV) or (V):

R and R7, the same or different from each other, represent a linear or branched C1-C10 alkyl group, said alkyl group possibly substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups wherein X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxy groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amino groups, Ν, Ν-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group;

R1 and R2, the same or different from each other, represent a linear or branched C1-C10 alkyl group, said alkyl group possibly substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups wherein X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxy groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C10 alkenyl group; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (Χ ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2, 6,6-tetramethylpiperidine group; a linear or branched C1-C6 alkoxy group; an amino N-alkyl (C1-C6) group; a Ν, Ν-dialkyl (C1-C6) amino group; or, R1 and R2, considered together with the carbon atom to which they are bonded, represent a C4-C10 cycloalkyl group, said cycloalkyl group possibly substituted with halogen atoms selected from fluorine, chlorine and bromine, or with hydroxyl groups, alkoxy groups Linear or branched C1-C6, carboxylic groups, cyano groups, amino groups, amino N-alkyl (C1-C6) groups, N, N-dialkyl (C1-C6) amino groups; a Ν, Ν-dialkyl (C1-C6) amide group; an aryl group selected from phenyl and biphenyl; a cyan group;

R3, R4, R5 and R6, the same or different from each other, represent a hydrogen atom; a halogen atom selected from fluorine, chlorine, bromine and iodine; a linear or branched C1-C6 alkyl group, said alkyl group optionally substituted with 1-6 halogen atoms selected from fluorine, chlorine and bromine, or with C (X'3) groups in which X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxyl groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X'3) groups in which X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a hydroxyl group; a linear or branched C1-C6 alkoxy group; an amino group; an amino N-alkyl (C1-C6) group; a Ν, Ν-dialkyl (C1-C6) amino group; a piperidine, piperazine or morpholine group; a C1-C6 carboxyalkyl group; a C2-C6 carboxyalkenyl group; a carboxyamide group; an N-alkyl (C1-C6) carboxyamide group; a Ν, Ν-dialkyl (C1-C6) carboxyamide group; a cyan group; a nitro group; a sulfonic group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with N, N-dialkyl (C1-C6) amino groups, linear or branched C1-C6 alkoxyl groups, hydroxyl groups, linear or branched C1-C6 alkyl groups ; an acyl group of the alkyl ketone, ary ketone or benzyl ketone type; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group, said alkenyl group optionally substituted with one or two N, N-dialkyl- (C1-C6) -4-aniline groups; an N-2,3-dihydroindoline group; a linear or branched C1-C6 thioether group;

two consecutive substituents between R3 and R6 can represent the melting points with other aromatic, heterocyclic or quinonic rings;

P represents a monocyclic or polycyclic aromatic nucleus, belonging to one of the following types: benzene represented by the general formula (VI); naphthalene represented by the general formula (VII); quinolinic represented by the general formula (VIII); isoquinoline represented by the general formula (IX); coumarin represented by the general formula (X); quinazoline represented by the general formula (XI); phenanthrene represented by the general formula (XII); anthracenic represented by the general formula (XIII); or a group having a general formula (XIV);

whose :

at least two contiguous substituents between R8 and R13, R14 and R21, R22 and R28, R29 and R35, R36 and R41, R42 and R47, R48 and R57, R58 and R67, R68 and R75, represent the points of fusion with the ring oxazine or pyranic, the other substituents having the meaning described for the substituents R3, R4, R5 and R6;

X1 represents an oxygen atom; an atom of sulfur; an atom of selenium; an NH group; an NRa group in which Ra represents a linear or branched C1-C10 alkyl group;

Y represents CH or a nitrogen atom; or R'2 represents a compound having general formula (XV):

where R t r r

and R 10, the same or different from each other, represent a hydrogen atom; a linear or branched C1-C10 alkyl group, said alkyl group optionally substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxyl groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amino groups, Ν, Ν-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (Χ ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group;

provided that at least one of the substituents R'2 represents a photochromic compound having general formula (II) and at least one of the substituents R'2 represents a compound having general formula (XV).

Photochromic compounds having general formula (I) preferred for the purpose of the present invention are those in which:

X represents an oxygen atom;

- R'1 represents a methyl;

R'2 represents an OH group; a photochromic compound having general formula (II); a compound having general formula (XV);

R 'represents a linear or branched C1-C4 alkyl group; a linear or branched C2-C4 acyl group; a linear or branched C2-C4 heteroalkyl group in which the heteroatom is selected from nitrogen, oxygen, sulfur and selenium; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group;

R '' represents a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, or a phenyl group;

Y represents a nitrogen atom; or CH;

P 'represents one of the groups having general formula (III), (IV) or (V) in which:

R and R7, the same or different from each other, represent one of the following groups: methyl, ethyl, isopropyl, 2-allyl, 2-metallyl, 2-hydroxyethyl, 2-carboxymethyl, phenyl, 4-N, N-dimethylaminoanilino, 4- methoxybenzene, 4-cyanobenzene;

R1 and R2, the same or different from each other, represent a methyl or phenyl group; or, considered together with the carbon atom to which they are bonded, they represent a cyclohexyl group;

R3, R4, R5 and R6, the same or different from each other, represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or one of the following groups: methyl, isopropyl, hydroxyl, methoxy, N , N-dimethylamino, piperidino, morpholino, carboxyl, carboxymethyl, N, N-dimethylcarboxyamide, cyano, nitro, methylketone, phenylketone, phenyl;

P represents one of the groups having general formula from (VI) to (XIV), in which:

(a) two contiguous substituents between R8 and R13, R14 and R21, R22 and R28, R29 and R35, R36 and R41, R42 and R47, R48 and R57, R58 and R67, R68 and R75, independently represent the melting points with the oxazine or pyran ring; and the other substituents each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or one of the following groups: methyl, isopropyl, hydroxyl, methoxy, 2-hydroxyethyl, 2- ( meth) allyl, (meth) acryl, piperidino, morpholino, N, N-dimethylamino, carboxyl, carboxymethyl, N, N-dimethylcarboxamido, cyano, nitro, methylketone, ethylketone, phenylketone, methylthiol;

(b) two contiguous substituents between R8 and R13, R1 and R21, R22 and R28, R29 and R35, R36 and R41, R42 and R47, R48 and R57, R58 and R67, R68 and R75, other than those reported in point ( a), represent the melting points with a benzene or quinone ring;

- X1 represents an oxygen atom; an atom of sulfur; an atom of selenium; an NH group; R '' 'represents a hydrogen atom; a methyl;

R '' '1, R' '' 2, R '' '3 and R' '' 4 represent a methyl;

R '' '5, R' '' 6, R '' '7, R' '9 and R "'10 represent a hydrogen atom;

R '' 'a represents a C3-C8 1-alkenyloxy group.

Specific examples of preferred compounds according to the present invention are:

Compound having formula (Ia):

Compound having formula (Ib):

Compound having formula (Ic):

A further object of the present invention is a process for the preparation of photochromatic compounds having general formula (I).

Photochromic compounds having general formula (I) can be prepared by condensation of photochromatic compounds having general formula (II):

in which the substituents R ', R' ', P, P' and Y have the same meanings described above, and of compounds having general formula (XV):

where in which R '' ', R' '' 1, R '' '2, R' '' 3, R '' '4, R' "5, R '" 6, R' "7, R" '8, R' "9 and R '" 10 have the same meanings described above, with silylated tetramers having general formula (I'a):

in which the substituents R'i and X have the same meanings described above, in the presence of an inert organic solvent such as, for example, acetone, acetonitrile, ethyl alcohol, isopropanol, toluene, dioxane, xylene, or a mixture of said solvents , at a temperature comprised between 50 ° C and 100 ° C, preferably between 60 ° C and 80 ° C, for a time comprised between 1 hour and 10 hours, preferably between 2 hours and 5 hours. The reaction product thus obtained is generally purified on a silica column, and subsequent crystallization from a solvent such as, for example, acetone, toluene, pentane, heptane, diethyl ether, or by repeated precipitation with methanol and dried with toluene.

Photochromic compounds having general formula (II) are obtained by condensation of isoindoline compounds having general formula (XVI), or of indolinic compounds having general formula (XVII), or of compounds derived from propargyl alcohol having general formula (XVIII), or of compounds derived from α, β-unsaturated aldehydes having general formula (XIX), with nitrous compounds or aldehyde compounds having general formula (XX), or with hydroxy-aryl compounds having general formula (XXI), to give the respective photochromatic compounds having general formula (XVIa), (XVIIa) and (XVIIIa), reported in Schemes 1-4:

DIAGRAM 1

in which the substituents R, from R1 to R7, R '', Y and P have the same meanings described above and Y 'represents a group NO or CHO.

Said condensation reaction is carried out in the presence of an inert organic solvent such as, for example, ethyl alcohol, isopropanol, toluene; acetonitrile, or a mixture of said solvents, and in the presence of an amine such as, for example, triethylamine, morpholine, piperidine, or of an acid such as, for example, paratoluenesulfonic acid, sulfuric acid, acid alumina, or a metal complex such as, for example, titanium (IV) tetra-ethoxide, at a temperature between 50 ° C and 100 ° C, preferably between 60 ° C and 75 ° C, for a time between 1 hour and 10 hours, preferably between 2 hours and 3 hours. The reaction product thus obtained is generally purified by elution on a silica column and subsequent crystallization from a solvent such as, for example, acetone, toluene, hexane, heptane, pentane, diethyl ether, dichloromethane.

The isoindolinic compounds having general formula (XVI) can be prepared according to processes known in the art described, for example, in: "Tetrahedron" (1966), Vol. 22, p. 2481; "Journal of Organic Chemistry" (1979), Vol. 44, p. 1519; «Angewandte Chemie International» (1968), Vol. 7, p. 373.

The indolinic compounds having general formula (XVII) can be prepared by reaction of 2,3,3-trimethylindolenine compounds with an alkyl or (meth) allyl halide as described, for example, in the Japanese patent application JP 03/176467.

The isoindolinic compounds having general formula (XVI) and the indolinic compounds having general formula (XVII), usually, are conserved in the form of salts such as, for example, iodides, bromides, chlorides, since the free base is very oxidable at 'air.

Compounds derived from propargyl alcohol having general formula (XVIII) can be prepared by reaction of ketone compounds with sodium acetylide in xylene or with a lithium acetylide / ethylenediamine complex as described, for example, in US patents 5,585,042 and 5,238,981.

Compounds derived from α, β-unsaturated aldehydes having general formula (XIX) can be prepared according to processes known in the art as described, for example, in Japanese patent application JP 48/016481; or in «Organic Synthesis» (1970), Vol. 50, p. 66.

The nitro compounds having general formula (XX) can be prepared by reaction of phenolic compounds with nitrous acid or with butyl nitrite, as described, for example, in the Italian patent IT 1,176,858.

The aldehyde compounds having general formula (XX) can be prepared by the reaction of phenolic compounds with paraiormaldehyde, hexamethylenetetramine, or acetic acid, followed by the addition of an aqueous solution of 60% -70% sulfuric acid, as described, for example, in the German patent DE 2,425,430.

The hydroxy-aryl compounds having general formula (XXI) are usually commercially available products such as, for example, β-naphthol or phenol.

Specific examples of isoindoline compounds having general formula (XVI), or of indolinic compounds having general formula (XVII), are the following:

Specific examples of nitrous compounds having general formula (XX) are the following:

The compounds having general formula (XV) can be prepared according to processes known in the art described, for example, in US 4,684,726, US 4,946,880 and US 5,051,458.

A specific example of a compound having general formula (XV) is the following:

The photochromic compounds having general formula (I) object of the present invention are products, oily or crystalline, colorless or slightly yellow colored.

Their solutions in common organic solvents such as, for example, benzene, toluene, methanol, ethanol, when not exposed to light sources, are colorless or slightly yellow colored. These solutions, if exposed to a light source, both visible and ultraviolet, take on a blue color. The coloring quickly decays when the light source is removed.

The photochromatic compounds having general formula (I) can be applied on the surface or incorporated in bulk into the desired articles, by means of techniques already known in the art and described below.

Some polymeric photochromatic products can be obtained with molding techniques such as, for example, injection or compression, starting from polymers in which one or more photochromic compounds having general formula (I) are homogeneously dispersed in mass.

Alternatively, the photochromic compounds having general formula (I) can be dissolved in a solvent together with the polymeric material such as, for example, polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, cellulose acetate butyrate or epoxy resin, polysiloxane, urethane. The mixture thus obtained is deposited on a transparent support to form, after evaporation of the solvent, a photochromic coating.

The photochromic compounds having general formula (I) can also be added to a polymerizable monomer such as, for example, a (meth) acrylic or allyl carbonate monomer, so that, after polymerization carried out in the presence of a suitable initiator such as, for example, azo-bis- (isobutyronitrile) in the case of the (meth) -acrylic monomer or of a peroxyketal in the case of the allyl carbonate monomer, they are uniformly incorporated in the resin formed.

Finally, the photochromatic compounds having general formula (I), can be applied to a transparent substrate such as, for example, polycarbonate, polymethyl methacrylate or polydethylene glycol bis (allyl carbonate), by surface impregnation obtained by contacting the substrate, at a suitable temperature, with a solution or dispersion containing one or more photochromatic compounds having general formula (I), operating according to a methodology described, for example, in US patent No. 5,130,353.

The photochromic compounds having general formula (I) object of the present invention have the characteristic of being able to be incorporated in mass 0 by one of the techniques described above, in various organic polymers such as, for example, high density polyethylene (HDPE), polyethylene a low density (LDPE), ethylene-vinyl acetate copolymer, polyethers amides, polypropylene, polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, cellulose acetate butyrate, epoxy resins, polysiloxane or urethane, polycarbonate, polyethylene glycol bis (allyl carbonate) , polyesters, polystyrene, vinyl polychloride, polyethylacrylate, silicone polymers.

Therefore, a further object of the present invention are the polymeric compositions comprising the aforementioned polymeric materials and the aforementioned photochromic compounds having general formula (I) and the photochromatic articles obtained from their processing.

The photochromatic compounds having general formula (I) object of the present invention are added to the aforesaid polymeric compositions in quantities ranging from 0.01% to 5% by weight, preferably from 0.1% to 2% by weight, on the weight of said polymer compositions.

The photochromic compounds having general formula (I) object of the present invention can also be added to compositions for covering or painting ("coating compositions"), such as, for example, paints, lacquers, varnishes or lacquers based on hybrid polysiloxanes and / or gels silica, plastic-based compositions. Therefore, a further object of the present invention are the compositions for covering or painting ("coating compositions"), such as, for example, paints, lacquers, varnishes or lacquers based on hybrid polysiloxanes and / or silica gel, compositions based on plastics, comprising said photochromic compounds.

The photochromic compounds having general formula (I) object of the present invention are added to the aforesaid compositions for covering or painting in a quantity comprised between 0.01% and 5% by weight, preferably between 0.1% and 2% by weight, by weight. of said compositions for covering or painting.

The paints or lacquers based on hybrid polysiloxanes and / or silica gel are obtained by means of the "sol-gel" process described, for example, by M. Nogami, Y. Abe in: "Journal of Materials Science" (1995), Vol. 30, pp. 5789-5792.

The above compositions for covering or painting can be applied to the substrate (metal, plastic, wood, etc.) through conventional methods such as, for example, brush ("brushing"), spray, pouring ("pouring"), dipping ("dipping" ) or electrophoresis.

The photochromic compounds having general formula (I) object of the present invention can optionally be used in the presence of the usual additives for organic polymers such as, for example, phenolic antioxidants, sterically hindered amines, benzotriazoles, benzophenones, phosphites or phosphonites.

The photochromic compounds having general formula (I) object of the present invention which, as already mentioned above, are colorless or slightly yellow colored, can be used as they are, in mixture with each other, or in combination with other suitable organic photochromic compounds in a way to obtain, after activation, the formation of colors such as brown and gray. For this purpose, the photochromatic compounds belonging to the class of spiro-indolino-oxazines or spiro-pyranes described in the art are particularly useful, such as, for example, in US patent No. 5,066,818.

In order to better understand the present invention and to put it into practice, some illustrative examples are given below which are not to be considered in any way limiting the scope of the invention itself.

EXAMPLE 1

Preparation of the compound having formula (XVIIa) -1:

In a 250 ml flask, equipped with reflux cooler and mechanical stirrer, 16 g of 2,7-dihydroxynaphthalene, 7.0 g of sodium nitrate, 100 ml of water and 4.0 g of sodium hydroxide are charged.

The above mixture is stirred, under a nitrogen atmosphere, until dissolution. Subsequently, 10.7 g of sulfuric acid diluted in 30 ml of water are added dropwise and the reaction temperature is maintained between 0 ° C and 5 ° C. After 30 minutes at said temperature, the reaction raw product is filtered, washed with water and dried in air. 18.6 g of a dark brown powder corresponding to 2,7-dihydroxy-1-nitrous-naphthalene are obtained.

18.6 g of 2,7-dihydroxy-1-nitrous-naphthalene are mixed with 17 g of 1,3,3-trimethyl-2-methylene-indoline and 30 ml of isopropyl alcohol: the mixture obtained is kept for 3 hours at reflux.

At the end of the reaction the solvent is removed by distillation under vacuum and, subsequently, 40 ml of toluene and 2.0 g of activated carbon are added. Said mixture is heated to 70 ° C for 15 minutes: the reaction raw product is filtered, concentrated and cooled.

The precipitated crude product is filtered obtaining 7.0 g of a white solid product corresponding to the Compound having formula (XVIIa) -1 which is identified by gas-mass (molecular weight = 344).

EXAMPLE 2

Preparation of the compound having formula (XVIIa) -2:

6.9 g of Compound (XVIIa) -1 obtained as described in Example 1, 25 ml of toluene, 25 ml of acetonitrile and 4 ml of triethylamine obtaining a not completely homogeneous solution. Said solution is kept under nitrogen flow to avoid oxidizing the product.

The aforesaid solution is heated to 20 ° C and a solution of 1.8 g of acryloyl chloride in 10 ml of toluene is added by dropping, obtaining a crystalline precipitate. After 10 minutes, 50 ml of water and 5.0 g of sodium carbonate are added, the mixture is stirred and the two phases are separated.

The organic phase is concentrated under vacuum to obtain a dark oil which is cooled.

The precipitated crude product is filtered obtaining 6.3 g of a white solid product corresponding to the Compound having formula (XVIIa) -2 which is identified by gas-mass (molecular weight = 398.

EXAMPLE 3

Preparation of the 3, 3-dimethyl-N-nethyl-allyl-2-methylene-indoline iodide having formula (XVII ') -A:

In a closed 100 ml tube, 7.2 g of 2,3,3-trimethylindolenine, 8.1 g of potassium iodide, 5.4 g of allylamine hydrochloride, 20 ml of water and 12 ml of acetonitrile are loaded.

The above mixture is heated to 90 ° C for 8 hours. At the end, the crude obtained is washed with water, toluene and hydrochloric acid up to pH 7.

The aqueous phase is further washed with toluene, treated with aqueous sodium hydroxide (30% solution) until reaching pH 14 and with toluene. The organic phases obtained are concentrated and dried.

A pink-brown oil is obtained (yield: 8.3 g) corresponding to the iodide of 1,1-dimethyl-N-methyl-allyl-2-methylene-indoline having formula (XVII ') - A. The free base, corresponding to the compound having formula (XVII '), is identified by gas-mass (molecular weight = 213). EXAMPLE 4

Preparation of the compound having formula (XVIIa) -3:

1.7 g of the 1,1-dimethyl-N-methyl-allyl-2-methylene-endoline iodide obtained as described in Example 3 are charged into a 250 ml flask, equipped with reflux refrigerant and mechanical stirrer, 1.04 g of 1-nitrous-2-naphthol, 1 g of triethylamine and 8 ml of toluene.

The above mixture is heated to 90 ° C and kept at this temperature, under stirring, under a nitrogen atmosphere, for 6 hours. The reaction crude obtained is pulled to dryness and repeatedly extracted with boiling heptane added with 1 g of activated carbon. The heptane extracts are concentrated and boiled with another 0.6 g of activated carbon.

The reaction raw product obtained is filtered and subsequently purified by passing over a silica column eluting with a toluene / hexane mixture in a 1/1 ratio.

An almost pure photochromic product (yellow-white solid) is obtained which is further purified by crystallization from toluene.

After crystallization, 1.2 g of a white solid product are obtained corresponding to the compound having formula (XVIIa) -3 which is identified by gas-mass (molecular weight = 368).

EXAMPLE 5

Preparation of the 1,1,4,7-tetramethyl-N-allyl-3-methylene-isoindoline iodide having formula (XVI ') - A:

In a 100 ml flask, equipped with reflux cooler and mechanical stirrer, 40 g of acetonylacetone, 16 g of allylamine hydrochloride, 20 ml of water and 12 ml of ethyl alcohol are charged.

The above mixture is heated to 80 ° C, under a nitrogen atmosphere, for 24 hours. At the end, the mixture is cooled and subsequently extracted with 30 ml of hexane. The aqueous phase obtained is treated with aqueous sodium hydroxide (30% solution) until reaching pH 14: a yellow-white precipitate is thus formed which is quickly filtered and washed with 30 ml of water and 10 ml of hexane.

The product is dried under vacuum and stored in a nitrogen atmosphere: the yield is 31.5 g. Said product is identified as 1,3,4,7-tetramethyl-N-allyl-isoindoline by gas-mass (molecular weight = 213).

A quantity equal to 31.5 g of the aforesaid product is placed in a stainless steel autoclave from

100 ml together with 20 ml of toluene and 23.8 g of methyldide. The autoclave is heated to 85 ° C and everything is kept at this temperature, under a nitrogen atmosphere, for 6 hours. At the end, the autoclave is cooled to room temperature and the crude is filtered obtaining a crystalline precipitate which is washed with 20 ml of ethyl acetate and finally with 20 ml of hexane.

43.6 g of product are obtained corresponding to the iodide of 1,1,4,7-tetramethyl-N-allyl-3-methylene-isoindoline having formula (XVI ') - A. The free base, corresponding to Compound (XVI '), is identified by gas-mass (molecular weight = 227).

EXAMPLE 6

Preparation of the compound having formula (XVIa) -4:

COCH-, CH.

II

(XVIa) -4

In a 250 ml flask, equipped with a coolant

under reflux and mechanical stirrer, 4 g of the 1,1,4,7-tetramethyl-N-allyl-3-methylene-isoindoline iodide obtained as described in Example 5, 2,6 g of 1-nitrous -2-naphthol-6-propan (1) one, 2.3 g of triethylamine and 60 ml of toluene.

The above mixture is heated to 70 ° C and kept at this temperature, under stirring, under a nitrogen atmosphere, for 1 hour. The reaction crude obtained is filtered and subsequently purified by passing over a silica gel column, eluting with a heptane / ethyl acetate mixture in a 1/1 ratio.

An almost pure photochromic product (yellow solid) is obtained which is further purified by crystallization from toluene.

After crystallization, 2 g of a white solid product are obtained corresponding to the compound having formula (XVIa) -4 which is identified by gas-mass (molecular weight = 438).

EXAMPLE 7

Preparation of the compound having formula (Ia):

0.20 g of Aldrich 2,4,6,8-tetramethylcyclotetrasiloxane (95%), a catalytic quantity of the platinum-divinyltetramethyl-disiloxane complex, are charged into a 100 ml flask, equipped with reflux refrigerant and mechanical stirrer. 10 ml of anhydrous toluene. The mixture is kept at 80 ° C, under stirring and in a nitrogen atmosphere, for 5 minutes.

Subsequently, 0.36 g of the Compound having formula (XV ') dissolved in 10 ml of anhydrous toluene are added: the mixture obtained is kept at 100 ° C for 1 hour.

Subsequently, 0.7 g of Compound (XVIIa) -2 are added, obtained as described in Example 2, dissolved in 30 ml of anhydrous toluene: the mixture obtained is kept at 80 ° C for 4 hours. At the end the solvent is eliminated by evaporation under vacuum.

The reaction raw product obtained is purified by repeated precipitations with methanol and dried with toluene.

0.60 g of a product (brown solid) corresponding to the Compound having formula (Ia) are obtained which is identified by liquid chromatography coupled to a mass spectrometer (molecular weight = 1456.5) and NMR spectrum. The NMR data obtained are reported below:

<29> Si-NMR: OSi (CHn) 2O- at -20 ppm.

EXAMPLE 8

Preparation of the compound having formula (Ib):

0.20 g of Aldrich 2,4,6,8-tetramethylcyclotetrasiloxane (95%), a catalytic quantity of the platinum-divinyltetramethyl-disiloxane complex, are charged into a 100 ml flask, equipped with reflux refrigerant and mechanical stirrer. 10.0 ml of anhydrous toluene. The mixture is kept at 80 ° C, under stirring and in a nitrogen atmosphere, for 5 minutes.

Subsequently, 0.36 g of the Compound having formula (XV ') dissolved in 10 ml of anhydrous toluene are added: the mixture obtained is kept at 100 ° C for 1 hour.

Subsequently, 0.60 g of Compound (XVIIa) -3 are added, obtained as described in Example 4, dissolved in 40 ml of anhydrous toluene: the mixture obtained is kept at 80 ° C for 5 hours. At the end the solvent is eliminated by evaporation under vacuum.

The reaction raw product obtained is purified by repeated precipitations with methanol and dried with toluene.

0.48 g of a product (brown oil) corresponding to the Compound having formula (Ib) are obtained which is identified by liquid chromatography coupled to a mass spectrometer (molecular weight = 1238.5) and NMR spectrum. The NMR data obtained are reported below:

<29> Si-NMR: OSi (CHn) 2O- at -20 ppm.

EXAMPLE 9

Preparation of the compound having formula (Ic):

0.26 g of Aldrich 2,4,6,8-tetramethylcyclotetrasiloxane (95%), a catalytic quantity of the platinum-divinyltetramethyl-disiloxane complex, are charged into a 250 ml flask, equipped with reflux refrigerant and mechanical stirrer. 20 ml of anhydrous toluene. The mixture is kept at 80 ° C, under stirring and in a nitrogen atmosphere, for 5 minutes.

Subsequently, 0.65 g of the Compound having formula (XV ') dissolved in 25 ml of anhydrous toluene are added: the mixture obtained is kept at 100 ° C for 1 hour.

Subsequently, 0.45 g of Compound (XVIa) -4 are added, obtained as described in Example 6, dissolved in 40 ml of anhydrous toluene: the mixture obtained is kept at 70 ° C for 4 hours. At the end the solvent is eliminated by evaporation under vacuum.

The reaction raw product obtained is purified by repeated precipitations with methanol and dried with toluene.

0.81 g of a product (green oil) are obtained corresponding to the Compound having formula (Ic) which is identified by liquid chromatography coupled to a mass spectrometer (molecular weight = 1308.5) and NMR spectrum. The NMR data obtained are reported below:

<29> Si-NMR: OSi (CHn) 2O- at -20 ppm.

EXAMPLE 10

Evaluation of the photochromic activity.

The photochromic activity in ethanol, at 10 ° C, of the Compounds (Ia) - (Ic) obtained as described in Examples 7-9 is evaluated.

Solutions are prepared at a concentration equal to 10 <-4> M of the different Compounds (Ia) - (Ic) in ethanol and, subsequently, 2 ml of each solution are placed in a 1 cm quartz cell.

The quartz cell containing the solution is placed in a temperature control system, equipped with a magnetic stirrer (the solution is kept under stirring during the measurement). The spectrum of the activated and deactivated shapes and the discoloration kinetics are recorded with a UV / visible diode battery spectrophotometer (HP 8453) equipped with perpendicular optical fibers that give a continuous monochromatic irradiation. The light source is a high pressure Hg lamp and the wavelength of the radiation is determined by monochromatic filters. This system allows to simultaneously monitor the absorbance at all wavelengths.

By using the measurements obtained as described above and a calculation carried out with the GRAFit program of Erithaeus Software Ltd. for the mathematical treatment of the graphs, the following parameters are determined:

t1 / 2 (s): time in which the absorbency of the open merocyanine form is equal to half of the initial absorbance;

kΔ (s <_1>): constant of the speed of the closing thermal reaction of the oxazine ring; λ <ΡΜC> (nm): wavelength of maximum absorption of the open merocyanine form;

colourability: difference between the final absorbance and the initial absorbance of the open merocyanine form.

The data obtained by analyzing the Compounds (Ia) - (Ic) are compared with the data obtained using the Compounds (XVIIa) -2, (XVIIa) -3 and (XVIa) -4: the Compounds (Ia) - (Ic) show an increase in the value of t1 / 2 (s).

The data obtained are reported in Table 1.

TABLE 1

Claims (14)

CLAIMS 1. Photochromic compounds having general formula (I): in which: X represents an oxygen atom; an ato-mo of sulfur; an atom of selenium; an NH group; or an NRa group wherein Ra represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; R'1 represents a linear or branched C1-C10 alkyl group, said alkyl group optionally substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amino groups, Ν, Ν-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; R'2 represents a hydrogen atom; an OH group; or a photochromic compound having general formula (II): R 'represents a linear or branched C1-C10 alkyl group; a linear or branched C2-C10 acyl group; a linear or branched C2-C10 heteroalkyl group in which the heteroatom is selected from nitrogen, oxygen, sulfur and selenium; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; R '' represents a hydrogen atom; a halogen atom selected from fluorine, chlorine and bromine; a linear or branched C1-C6 alkyl group; a linear or branched C1-C6 alkoxy group; a phenyl group; a phenoxy group; P 'represents one of the following groups having general formula (III), (IV) or (V): R and R7, the same or different from each other, represent a linear or branched C1-C10 alkyl group, said alkyl group possibly substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups wherein X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxy groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amino groups, N, N-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; R1 and R2, the same or different from each other, represent a linear or branched C1-C10 alkyl group, said alkyl group possibly substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups wherein X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxy groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C10 alkenyl group; a C00R'a ester group wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-Cm alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6tetramethylpiperidine group; a linear or branched C1-C6 alkoxy group; an amino N-alkyl (C1-C6) group; an N, N-dialkyl (C1-C6) amino group; or, R1 and R2, considered together with the carbon atom to which they are bonded, represent a C4-C10 cycloalkyl group, said cycloalkyl group possibly substituted with halogen atoms selected from fluorine, chlorine and bromine, or with hydroxyl groups, alkoxy groups Linear or branched C1-C6, carboxylic groups, cyano groups, amino groups, amino N-alkyl (C1-C6) groups, Ν, Ν-dialkyl (C1-C6) amino groups; a Ν, Ν-dialkyl (C1-C6) amide group; an aryl group selected from phenyl and diphenyl; a cyan group; R3, R4, R5 and RÉ, the same or different from each other, represent a hydrogen atom; a halogen atom selected from fluorine, chlorine, bromine and iodine; a linear or branched C1-C6 alkyl group, said alkyl group optionally substituted with 1-6 halogen atoms selected from fluorine, chlorine and bromine, or with C (X'3) groups in which X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxyl groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X'3) groups in which X 'is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a hydroxyl group; a linear or branched C1-C6 alkoxy group; an amino group; an amino N-alkyl (C1-C6) group; a Ν, Ν-dialkyl (C1-C6) amino group; a piperidine, piperazine or morpholine group; a C1-C6 carboxyalkyl group; a C2-C6 carboxyalkenyl group; a carboxyamide group; an N-alkyl (C1-C6) carboxyamide group; a Ν, Ν-dialkyl (C1-C6) carboxyamide group; a cyan group; a nitro group; a sulfonic group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with Ν, Ν-dialkyl (C1-C6) amino groups, linear or branched C1-C6 alkoxyl groups, hydroxyl groups, linear or branched C1-C6 alkyl groups ; an acyl group of the alkyl ketone, ary ketone or benzyl ketone type; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group, said alkenyl group optionally substituted with one or two N, N-dialkyl- (C1-C6) -4-aniline groups; an N-2,3-dihydroindoline group; a linear or branched C1-C6 thioether group; two consecutive substituents between R3 and R6 can represent the melting points with other aromatic, heterocyclic or quinonic rings; P represents a monocyclic or polycyclic aromatic nucleus, belonging to one of the following types: benzene represented by the general formula (VI); naphthalene represented by the general formula (VII); quinolinic represented by the general formula (VIII); isoquinoline represented by the general formula (IX); coumarin represented by the general formula (X); quinazoline represented by the general formula (XI); phenanthrene represented by the general formula (XII); anthracenic represented by the general formula (XIII); or a group having a general formula (XIV); in which: at least two contiguous substituents between R8 and R13, R14 and R21, R22 and R28, R29 and R35, R36 and R41, R42 and R47, R48 and R57, R58 and R67, R68 and R75, represent the points of fusion with the ring oxazine or pyranic, the other substituents having the meaning described for the substituents R3, R4, R5 and R6; X1 represents an oxygen atom; an atom of sulfur; an atom of selenium; an NH group; an NRa group in which Ra represents a linear or branched C1-C10 alkyl group; Y represents CH or a nitrogen atom; or R'2 represents a compound having general formula (XV): where R '' ' and R equal to or different from each other, represent a hydrogen atom; a linear or branched C1-C10 alkyl group, said alkyl group optionally substituted with 1-10 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C6 alkoxyl groups, carboxyl groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; a vinyl group; a (meth) allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; a linear or branched C2-C6 alkenyl group; an aryl group selected from phenyl, biphenyl and naphthyl, said aryl group optionally substituted with linear or branched C1-C6 alkoxy groups, carboxylic groups, amine groups, N, N-dialkyl (C1-C6) amino groups; an ester group COOR'a wherein R'a represents a linear or branched C1-C10 alkyl group; a benzyl group, said benzyl group optionally substituted with 1-5 halogen atoms selected from fluorine, chlorine and bromine, or with C (X ') 3 groups in which X' is selected from fluorine, chlorine and bromine, hydroxyl groups, linear or branched C1-C10 alkyls, linear or branched C1-C6 alkoxyl groups, carboxylic groups, cyano groups, or with a 2,2,6,6-tetramethylpiperidine group; provided that at least one of the substituents R'2 represents a photochromic compound having general formula (II) and at least one of the substituents R'2 represents a compound having general formula (XV). 2. Photochromic compounds having general formula (I) according to claim 1, wherein; X represents an oxygen atom; R'1 represents a methyl; R'2 represents an OH group; a photochromic compound having general formula (II); a compound having general formula (XV); R 'represents a linear or branched C1-C4 alkyl group; a linear or branched C2-C4 acyl group; a linear or branched C2-C4 heteroalkyl group in which the heteroatom is selected from nitrogen, oxygen, sulfur and selenium; a (meth) -allyl group; a (meth) acrylic group; a C3-C8 1-alkenyloxy group; R '' represents a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, or a phenyl group; Y represents a nitrogen atom; or CH; P 'represents one of the groups having general formula (III), (IV) or (V) in which; R and R7, the same or different from each other, represent one of the following groups: methyl, ethyl, isopropyl, 2-allyl, 2-metallyl, 2-hydroxyethyl, 2-carboxymethyl, phenyl, 4-N, N-dimethylaminoanine, 4- methoxybenzene, 4-cyanobenzene; R1 and R2, the same or different from each other, represent a methyl or phenyl group; or, considered together with the carbon atom to which they are bonded, they represent a cyclohexyl group; R3, R4, R5 and R6, the same or different from each other, represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or one of the following groups: methyl, isopropyl, hydroxyl, methoxy, N , N-dimethylamino, piperidino, morpholino, carboxyl, carboxymethyl, N, N-dimethylcarboxyamide, cyano, nitro, methylketone, phenylketone, phenyl; P represents one of the groups having general formula from (VI) to (XIV), in which: (a) two contiguous substituents between R8 and R13, R1 and R21, R22 and R28, R29 and R35, R36 and Rm R42 and R47, R48 and R57, R58 and R67, R68 and R75, independently represent the melting points with the oxazine or pyranic ring; and the other substituents each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or one of the following groups: methyl, isopropyl, hydroxyl, methoxy, 2-hydroxyethyl, 2- ( meth) allyl, (meth) acryl, piperidino, morpholino, N, N-dimethylamino, carboxyl, carboxymethyl, N, N-dimethylcarboxamido, cyano, nitro, methylketone, ethylketone, phenylketone, methylthiol; (b) two contiguous substituents between Rs and R13, R1e and R21, R22 and R28, R29 and R35, R36 and R41, R42 and R47, R48 and R57, R58 and R67, R68 and R75, other than those reported in point (a), represent the melting points with a ring benzene or chinone; Xi represents an oxygen atom; an atom of sulfur; an atom of selenium; an NH group; R '' 'represents a hydrogen atom; a methyl; R '' 'i, R' '' 2 / R '' '3 and R' '' 4 represent a methyl; R "'s, R'" e, R '"7>, R'" 9 and R '' '10 represent a hydrogen atom; R, / 8 represents a C3-CB 1-alkenyloxy group. 3. Photochromic compound having general formula (I) according to claim 1 or 2, consisting of the compound having formula (Ia): 4. Photochromic compound having general formula (I) according to claim 1 or 2, consisting of the compound having formula (Ib): 5. Photochromic compound having general formula (I) according to claim 1 or 2, consisting of the compound having formula (Ic): 6. Process for the preparation of the photochromic compounds having general formula (I) according to any one of the preceding claims, comprising the condensation of photochromatic compounds having general formula (II): in which the substituents R ', R' ', P, P' and Y have the same meanings described above, and of compounds having general formula (XV): where in which R '' ', R' '' i, R '' '2 r R' '' 3, R '' '4, R' "5, R '' '6, R"' 7, R '"8, R'" 9 and R "'10 have the same meanings described above, with silylated tetramers having general formula (I'a): wherein the substituents R'i and X have the same meanings described above, in the presence of an inert organic solvent, at a temperature ranging from 50 ° C to 100 ° C, for a time ranging from 1 hour to 10 hours. 7. Process according to claim 6, wherein the inert organic solvent is selected from: acetone, acetonitrile, ethyl alcohol, isopropanol, toluene, dioxane, xylene, or from mixtures of said solvents. 8. Process according to claim 6 or 7, wherein the reaction temperature is between 60 ° C and 80 ° C. 9. Process according to claim 6, 7 or 8, wherein the reaction time is between 2 hours and 5 hours. 10. Polymeric compositions comprising at least one photochromic compound according to any one of claims 1 to 9, and at least one organic polymer selected from among high density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, polyethers amides, polypropylene, polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, cellulose acetate butyrate, epoxy, polysiloxane or urethane resins, polycarbonate, polydethylene glycol bis (allyl carbonate), polyamides, polyesters, polystyrene, vinyl polychloride, polyethylacrylate, silicone polymers. 11. Compositions for covering or varnishing, such as varnishes, lacquers, varnishes or lacquers based on hybrid polysiloxanes and / or silica gel, compositions based on plastics, comprising one or more photochromic compounds having general formula (I) referred to in a any of claims 1 to 9. 12. Compositions according to claim 10 or 11, comprising additives for organic polymers selected from phenolic antioxidants, sterically hindered amines, benzotriazoles, benzophenones, phosphites or phosphonites. 13. Photochromic articles obtained from the processing of the compositions according to claims 10, 11 or 12. 14. Mixtures comprising at least one photochromic compound having general formula (I) according to any one of claims 1 to 9 and at least one photochromic compound belonging to the class of spiro-indolino-oxazines or spiro-pyranes.