Benzylidene-.gamma.-butyrolactones, process for their preparation and their use as UV absorber

The invention relates to modified benzylidene-.gamma.-butyrolactones, to a process for their preparation and to the use as UV absorber, for example in pharmaceutical and cosmetic compositions, sunscreens, daycare and haircare products, for improving industrial products, such as paints, surface coatings, plastics, textiles, packaging materials and rubbers.

FIELD OF THE INVENTION
 The invention relates to modified benzylidene-.gamma.-butyrolactones, to a
 process for their preparation and to the use as UV absorber, for example
 in pharmaceutical and cosmetic compositions, sunscreens, daycare and
 haircare products, for improving industrial products, such as paints,
 surface coatings, plastics, textiles, packaging materials and rubbers.
 BACKGROUND OF THE INVENTION
 Depending on their wavelength, UV rays are divided in UV-A rays (320-400
 nm) and UV-B rays (280-320 nm). The harmful effect, in particular the
 occurrence of sunburn (erythema), increases not only with the duration of
 exposure but also with decreasing wavelength and is thus significantly
 more strongly marked in the case of UV-B radiation than in the case of
 UV-A radiation. Since erythemas can occur even after short exposure to the
 sun, in some cases after 20-30 minutes, efficient protection against this
 radiation is of particular importance.
 For this area of UV protection, a number of UV-B absorbers are already
 known from the prior art. Examples mentioned are camphor derivatives,
 salicylic acid derivatives, benzophenones, cinnamates, benzimidazoles and
 triazines. One example of benzylidene-.gamma.-butyrolactones is described
 in European Patent Application EP-A 44970. These are compounds of the
 formula
 ##STR1##
 in which
 R is a C.sub.1 -C.sub.15 -alkyl radical, branched or unbranched, phenyl or
 benzyl.
 However, all of these compounds have the disadvantages that they are either
 in the form of a solid and thus have only limited solubility in the
 cosmetic preparations, exhibit only low absorption or have photostability
 which does not meet the necessary criteria and are thus unsatisfactory.
 SUMMARY OF THE INVENTION
 Accordingly, the object of the present invention is to provide improved
 UV-B absorbers. This object is achieved by
 benzylidene-.gamma.-butyrolactones of the general formula
 ##STR2##
 wherein
 R is hydrogen or C.sub.1 -C.sub.6 -alkyl or cycloalkyl, and
 R.sup.1 to R.sup.5 independently of one another are hydrogen, but at most
 4, are hydrogen at the same time, or C.sub.1 -C.sub.8 -alkyl or
 cycloalkyl, and also R.sup.1 /R.sup.2 and/or R.sup.3 /R.sup.4 can form a
 carbocyclic ring having from 5 to 7 ring atoms.
 According to the present invention, particular preference is given to
 benzylidene-.gamma.-butyrolactones in which the lactone ring is
 trisubstituted at R.sup.1, R.sup.3 and R.sup.4 by an alkyl, where an alkyl
 group includes at least one C.sub.2 chain. Likewise preferred are
 benzylidene-.gamma.-butyrolactones whose benzylidene ring is substituted
 in the para-position by a methoxy radical, and R.sup.1 is an ethyl
 radical, R.sup.2 is hydrogen, and R.sup.3 /R.sup.4 is a methyl radical.
 Specific benzylidene-.gamma.-butyrolactones compounds of the present
 invention include: p-Methoxybenzylidene-4-methyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-4-butyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-4,4-dimethyl-.gamma.-butyrolactone,
 p-methoxy-benzylidene-3,4-dimethyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3,4,4-trimethyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3-methyl-4-pentyl-.gamma.-butyrolactone,
 p-methoxybenzyl-idene-3-methyl-4-hexyl-.gamma.-butyrolactone,
 o,p-dimethoxybenzylidene-4-butyl-.gamma.-butyrolactone,
 o,p-dimethoxybenzylidene-4,4-dimethyl-.gamma.-butyrolactone,
 o,p-dimethoxybenzylidene-3,4-dimethyl-.gamma.-butyrolactone,
 m,p-dimethoxybenzylidene-4-butyl-.gamma.-butyrolactone,
 m,p-dimethoxybenzyl-idene-4,4-dimethyl-.gamma.-butyrolactone,
 m,p-dimethoxybenzylidene-3,4-dimethyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3-ethyl-4,4-dimethyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3,4-dimethyl-4-butyl-.gamma.-butyro-lactone,
 p-methoxybenzylidene-3,4-dimethyl-4-ethyl-.gamma.-butyrolactone.
 Particularly preferred benzylidene-.gamma.-butyrolactones include
 p-methoxy-benzylidene-3-ethyl-4,4-dimethyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3,4-dimethyl-4-butyl-.gamma.-butyrolactone,
 p-methoxybenzylidene-3,4-dimethyl-4-ethyl-.gamma.-butyrolactone.
 The benzylidene-.gamma.-butyrolactones according to the present invention
 can be prepared in accordance with the prior art by aldol condensation of
 substituted benzaldehydes, for example anisaldehyde, with correspondingly
 substituted .gamma.-butyrolactones, for example
 .beta.-ethyl-.gamma.,.gamma.-dimethyl-.gamma.-butyrolactone.
 Additionally, the benzylidene-.gamma.-butyrolactones according to the
 present invention are particularly suitable as UV absorbers and solvents
 for solid UV absorbers, which have relatively poor solubility within a
 pharmaceutical or cosmetic preparation. Accordingly, the present invention
 also provides compositions which comprise the above-mentioned
 benzylidene-.gamma.-butyrolactones and are suitable for protecting against
 harmful UV radiation. In this connection, the compositions according to
 the present invention can comprise one or more of the
 benzylidene-.gamma.-butyrolactones according to the invention.
 Preference is given to compositions which comprise from 0.1 to 15% by
 weight of benzylidene-.gamma.-butyrolactones according to the present
 invention, based on the total weight of the preparation. Particular
 preference is given to compositions comprising from 1 to 10% by weight,
 and most preferably comprising from 2 to 7% by weight, of
 benzylidene-.gamma.butyrolactone according to the present invention.
 According to the present invention, the above-mentioned compositions are
 preferably suitable as sunscreens or daycare products for protecting human
 skin and hair, in particular hair already predamaged by permanent waving,
 coloring and bleaching, against harmful UV radiation.
 According to the present invention, the compositions can also be mixed with
 additives known per se and/or known UV absorbers of other classes of
 substance and/or known pigments.
 Examples of common additives are emulsifiers, surface-active compounds,
 lanolin, petroleum jelly, water, triglycerides of fatty acids,
 polyethylene glycols, fatty alcohols, ethoxylated fatty alcohols, fatty
 acid ester such as, for example, isopropyl palmitate, isooctyl sterate,
 diisopropyl adipate etc., natural or synthetic oils or waxes, thickeners,
 such as, for example, hydroxyethylcellulose, bentonite, etc.,
 preservatives, moisturizers, vitamins, skin-lightening active ingredients
 such as, for example, hydroquinones, arbutin, kojic acid and derivatives,
 ascorbic acid and derivatives, glutathione, hydroxybenzaldoximes, e.g.,
 4-hydroxy-3-methoxybenzaldehyde oxime, antioxidants such as, for example,
 BHT, vitamin derivatives, catechol derivatives, e.g., epigallocatechol
 gallate or 3,4-dihydroxybenzaldehyde oxime, complexing agents such as, for
 example, EDTA and derivatives, insect repellents such as, for example,
 DEET or IR 3535, silicone oils, glycerol, ethyl alcohol and perfume oils.
 The list of additives is not limited to the examples given. Pigments which
 can be added are, for example, titanium dioxide, zinc oxide, pearlizing
 pigments or color pigments.
 Examples of traditional UV absorbers include p-aminobenzoic acid, ethyl
 p-amino-benzoate (25 mol) ethoxylated, 2-ethylhexyl
 p-dimethyl-aminobenzoate, ethyl p-aminobenzoate (2 mol) N-propoxylated,
 glycerol p-aminobenzoate, homomenthyl salicylate, 2-ethylhexyl salicylate,
 triethanolamine salicylate, 4-isopropylbenzyl salicylate, methyl
 anthranilate, ethyl diisopropylcinnamate, 2-ethylhexyl
 p-methoxy-cinnamate, methyl diisopropylcinnamate, isoamyl
 p-methoxycinnamate, p-methoxy-cinnamic acid diethanolamine salt, isopropyl
 p-methoxycin-namate, 2-ethylhexyl 2-cyano-3,3-diphenyl acrylate, ethyl
 2-cyano-3,3'-diphenyl acrylate, 2-phenyl-benzimidazolesulphonic acid and
 salts, 3-(4'-trimethylammonium)-benzylidene-bornan-2-one methylsulphate,
 terephthalylidene-dibornanesulphonic acid and salts,
 4-t-butyl-4'-methoxydibenzoylmethane, .beta.-imidazole-4(5)-acrylic acid
 (urocanic acid). 2-hydroxy-4-methoxybenzophenone,
 2-hydroxy-4-methoxybenzophenone-5-sulphonic acid,
 dihydroxy-4-methoxybenzophenone, 2,4-dihydroxy-benzophenone,
 tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone,
 2-hydroxy-4-n-octoxybenzophenone,
 2-hydroxy-4-methoxy-4'-methylbenzophenone,
 3-(4'sulpho)benzylidene-bornan-2-one and salts,
 3-(4'-methylbenzylidene)-d,1camphor, 3-benzylidene-d,1-camphor,
 4-isopropyldibenzoylmethane,
 2,4,6trianilino-(p-carbo-2'-ethylhexyl-1'-oxy)-1,3,5-triazine,
 phenylene-bis-benzimidazyl-tetrasulphonic acid disodium salt and N-[(2 and
 4)-[2-(oxoborn-3ylidene)methyl]benzyl]-acrylamide polymer, benzylidene
 malonate polymer,
 2,2'-methylene-bis-(6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-
 phenol), 2,2'-(1,4-phenylene)bis-1H-benzimidazol-4,6-disulphonic acid,
 monosodium salt,
 2,4-bis-((4-(2-ethyl-hexyloxy)-2-hydroxy)-phenyl)-6-(4-methoxyphenyl)-(1,3
 ,5)-triazine.
 UV absorbers which have proven to be particularly suitable for combination
 with the agents according to the present invention are 2-ethylhexyl
 p-methoxycinnamate, isoamyl p-methoxycinnamate,
 2-phenylbenzimidazolesulphonic acid, 3-(4'-methylbenzylidene)-d,1-camphor,
 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl salicylate,
 4-tert-butyl-4'-methoxydibenzoylmethane and
 phenylene-bis-benzimidazyl-tetrasulphonic acid disodium salt, indanylidene
 derivatives according to DE 19 631 863 and benzazol derivatives according
 to DE 19 648 010.
 The present invention further provides for the use of the agents according
 to the present invention in combination with conventional UV absorbers for
 enhancing the protection against harmful UV radiation above the degree of
 protection which is achieved using equal amounts of conventional UV
 absorbers alone or the agents alone (synergistic effect).
 Furthermore, the agents according to the present invention can also be
 combined with conventional UV absorbers which are used for the protection
 of industrial products, such as paints, surface coatings, plastics,
 textiles, packaging materials or rubber.
 Examples of such UV absorbers are compounds from the group consisting of
 benzotriazoles, benzophenones, triazines, cinnamic esters and
 oxalanilides.
 The compositions according to the present invention can be in the form of
 any currently customary cosmetic or pharmaceutical preparations. For
 example, they can be supplied as emulsion, milk, lotion, cream, gel,
 aerosol, shampoo, conditioner, intensive conditioner or spray.
 Surprisingly, the compositions which comprise
 benzylidene-.gamma.-butyrolactone in accordance with the present invention
 are characterized by a combination of desirable properties.
 The agents have the advantageous properties according to the present
 invention in that they have high UV protection even at low use
 concentrations, excellent photo-stability and thermal stability and good
 solubility in cosmetic solvents. In addition, the crystalline, oil-soluble
 UV absorbers have, in accordance with the present invention, excellent
 solubility in cosmetic solvents. The agents have, in accordance with the
 invention, good compatibility with cosmetic bass and good pH stability,
 are colorless, neutral in odor and water-resistant. In addition, the
 agents according to the present invention can be incorporated without
 problems into cosmetic preparations and exhibit good stability under use
 conditions and good compatibility with packaging materials. Moreover, the
 compositions according to the present invention do not cause any
 discoloration of textiles and can be washed out easily.
 The application is illustrated in more detail below by reference to the
 examples: