Process for the methylation of triazine compounds containing 2,2,6,6-tetramethylpiperidine groups

Abstract: Process for the methylation of compounds containing at least one group of the formula (I) by means of a mixture of formaldehyde and formic acid in a reaction medium consisting of an aromatic hydrocarbon solvent.

Description: The present invention relates to a novel process for the preparation of triazine compounds containing 1,2,2,6,6-pentamethylpiperidine groups. In particular, the present invention relates to a simple and convenient process for the preparation of 1,2,2,6,6-pentamethyl-4-piperidylaminotriazine compounds containing one or more triazine rings, which process is based on the methylation of the corresponding 2,2,6,6-tetramethylpiperidine derivatives by means of formaldehyde and formic acid and which is operated in an aromatic hydrocarbon solvent. Triazine derivatives of 2,2,6,6-tetramethyl-4-piperidylamine can be used as light stabilizers and heat stabilizers for synthetic polymers, as reported, for example, in US Patents 4,086,204 and 4,108,829 and EP-A-107,615. Moreover, it was shown in GB-A-2,194,237 that certain triazine derivatives of 1,2,2,6,6-pentamethyl-4-piperidylamine also have remarkable antioxidant properties in the case of polyolefines. Considerable interest has therefore arisen in an economical and industrially applicable process for the methylation of triazine derivatives of 2,2,6,6-tetramethyl-4-piperidylamine. It is known that numerous derivatives of 2,2,6,6-tetramethylpiperidine can be obtained starting from triacetoneamine (2,2,6,6-tetramethyl-4-piperidone). The methylation of these piperidine compounds in the 1-position has hitherto been carried out in various ways, the methylating agents used being methyl iodide, methyl sulfate, methyl p-toluenesulfonate, formaldehyde and formic acid (Eschweiler-Clarke reaction) or formaldehyde, hydrogen and a hydrogenation catalyst (reductive methylation). This last process is very advantageous for the methylation of simple derivatives of 2,2,6,6-tetramethylpiperidine, for example 2,2,6,6-tetramethyl-4-piperidinol, but it is not suitable for the preparation of more complex compounds. In this case, the only process feasible in practice is that based on the Eschweiler-Clarke reaction; this has in fact frequently been used for the preparation of various 1,2,2,6,6-pentamethylpiperidine compounds, as reported, for example, in US Patents 3,898,303, 3,904,581, 3,937,711, 4,107,139, 4,316,837 and 4,533,688 and in EP-A-103,193. The above mentioned process, which can be schematically represented by the reaction consists in heating the 2,2,6,6-tetramethylpiperidine, already isolated from the reaction mixture, for several hours with an excess of aqueous formaldehyde and formic acid, rendering the mixture alkaline to a pH>9 at the end of the reaction and then, by filtration, separating off the methylated product which, after repeated washing to remove the excess alkali, is finally dried. The process is long and costly and, therefore, a need is felt for providing a simpler and more economical process which can be used on an industrial scale. A very advantageous methylation process has now been found, which is particularly suitable for the preparation of 1,2,2,6,6-pentamethyl-4-piperidylaminotriazine compounds. Compared with the known state of the art, the process according to the present invention has various advantages which can be summarized as follows: a) direct use of the reaction mixture obtained from cyanuric chloride and 2,2,6,6-tetramethyl-4-piperidylamine in an aromatic hydrocarbon solvent containing the tetramethylpiperidine derivative, without isolation of the latter; b) use of a smaller excess of formaldehyde and formic acid; c) shortened reaction times; d) almost complete elimination of the CO₂ produced in the reaction; e) considerable reduction in the quantity of aqueous reflux; in fact, the use of a smaller excess of formic acid and the almost complete elimination of CO₂ from the reaction mixture permit a significant reduction in the quantity of inorganic base required to neutralize the methylated product, so that the quantity of by-products to be eliminated is reduced; f) higher purity of the product obtained, since complete methylation of the NH groups in the piperidine is assured; this corresponds to a higher yield of methylated product. The significant reduction in the working times, the use of smaller quantities of reagents and the higher yields make the process according to the present invention very attractive economically and hence suitable for use on an industrial scale. The present invention relates to a process for the methylation of compounds containing at least one group of the formula (I) by means of a mixture of formaldehyde and formic acid to give the corresponding compound containing at least one group of the formula (II) which comprises effecting the said methylation in an aromatic hydrocarbon solvent, simultaneously separating off the water of reaction and that contained in the reagents by azeotropic distillation, and the molar ratio of the NH groups in the piperidine of the formula (I), formaldehyde and formic acid being 1:1:1: to 1:2:2. In the process according to the present invention, the formaldehyde is preferably used as a 30-50 % (weight/volume) aqueous solution and the formic acid can contain up to 30 % (weight/volume) of water. The aromatic hydrocarbon solvent used is, for example, toluene, xylene or trimethylbenzene and preferably xylene. Those procedures are of particular interest in which the molar ratio of the NH groups in the piperidine of the formula (I), formaldehyde and formic acid is 1:1:1 to 1:1.3:1.3 and in particular 1:1:1 to 1:1.2:1.2. The reaction temperature is 80° to 150°C, preferably 90° to 130°C. When the reaction has ended, the unreacted formic acid and the residual CO₂ are e.g. neutralized with an aqueous solution of an inorganic base, preferably sodium hydroxide or potassium hydroxide. After the aqueous phase (containing the unreacted formaldehyde beside formate and carbonate) has been separated off, the organic phase is washed with water until neutral. The water which has remained in the organic phase is conveniently removed azeotropically and the solvent is evaporated to give the methylated product. The methylated product thus obtained can be used directly or, if desired, can be purified by usual methods, for example by crystallization. The formaldehyde for the methylation reaction is preferably free of methanol; this can be obtained from paraformaldehyde, for example by dissolving the latter in water in the presence of about 2-3 % of sodium hydroxide. It is also possible directly to use paraformaldehyde suspended in water in a quantity necessary to obtain a CH₂O concentration equal to 30-50 %. If NH groups bound directly to the triazine ring are also present in the compounds containing groups of the formula (I), a total or partial methylation of these groups may be possible, the extent of this methylation depending on the quantity of the reagents used and on the reaction temperature; higher temperatures favour this methylation. The compounds containing one or more groups of the formula (I) can be prepared by known methods, for example by reacting cyanuric chloride with 2,2,6,6-tetramethyl-4-piperidylamine, as described, for example, in US Patents 3,925,376, 4,086,204, 4,108,829, 4,477,615 and 4,547,548. In particular, compounds which contain groups of the formula (II) and which can be prepared by the present invention are: 1) Compounds of the formula (III) in which X and X₁, which can be identical or different, are one of the groups -OR₂ , -SR₂ and where R₁ is hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, phenyl, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which can be identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, C₂-C₄alkyl mono-substituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, or benzyl, or R₃ and R₄, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, m is an integer from 1 to 6 and, if m is 1, X₂ is as defined above for X and X₁ or is Cl or Br and, if m is 2, X₂ is one of the groups of the formulae (IV)-(IVe) in which R₅ is as defined above for R₁, and R₆, R₈ and R₁₁, which can be identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl or are benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, xylylene, C₄-C₁₂alkylene which is interrupted by one, two or three oxygen atoms or N-R₁₃ groups, R₁₃ being C₁-C₁₂alkyl or cyclohexyl, R₉ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, phenylene, C₁₃-C₂₆alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, R₁₀ is hydrogen or methyl, n is an integer from 2 to 6, and, if m is 3, X₂ is one of the groups in which R₁₄, R₁₇, R₁₈, R₁₉, R₂₀, R₂₂, R₂₃ and R₂₅, which can be identical or different, are as defined for R₆ and R₈, and R₁₅, R₁₆, R₂₁ and R₂₄, which can be identical or different, are C₂-C₁₂alkylene, or R₁₅ and R₁₆ are C₄-C₆alkylene which is interrupted by an N-CH₃ group, r and s, which can be identical or different, are integers from 2 to 6 and t is zero or 1, and, if m is 4, 5 or 6, X₂ is a group where R₂₆ and R₂₉, which can be identical or different, are as defined for R₆ and R₈, and R₂₇ and R₂₈, which can be identical or different, are C₂-C₁₂alkylene and v is 1, 2 or 3, or, if m is 4, X₂ is additionally one of the groups where R₃₀ and R₃₃, which can be identical or different, are as defined above for R₆ and R₈, and R₃₁ and R₃₂, which can be identical or different, are C₂-C₁₂alkylene and X is as defined above, or, if m is 6, X₂ is additionally one of the groups where R₃₀, R₃₁, R₃₂ and R₃₃ are as defined above, with the proviso that, in these compounds of the formula (III), at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the groups X, X₁ and X₂. 2) Compounds of the formula (V) in which X₃ is one of the groups of the above formulae (IVa), (IVb), (IVc) and (IVd) or a group of the formula in which R₁₁, R₁₈, R₁₉, R₂₀, n, r, s and t are as defined above, R₁₂ is as defined above for R₁₁, p is as defined above for n and q is zero or 1, X₄ is as defined above for the groups X and X₁, and w is a number from 2 to 50, the first end group attached to the triazine group being, for example, Cl, ONa, OK, a group X₄ or one of the groups -O-R₉-OH, in which R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, R₁₈, R₁₉, R₂₀, n, p, q, r, s and t are as defined above, the second end group attached to the radical X₃ being, for example, methyl, OH or a group where A has one of the definitions given above for the first end group and X₄ is as defined above, with the proviso that, in these compounds of the formula (V) at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the groups X₃ and X₄. 3) Polytriazines containing recurring units of the formulae (VI) and (VII) and having a molecular weight between 1000 and 20,000, in which the (VI):(VII) molar ratio is 4:1 to 1:4, X₅ and X₈, which can be identical or different, are as defined above for X₃, X₆ is as defined above for X and X₁, X₇ is C₂-C₁₂alkylene, a group aliphatic C₂-C₁₂-diacyl, -CH₂CO-, a group -COO-R₉-OOC- with R₉ as defined above, or X₇ is a group with X₉ as defined above for X and X₁, with the proviso that, in these compounds, at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the radicals X₅, X₆ and X₈. 4) Compounds of the formula (VIII) where X₁₀ is as defined above for X₇, R₃₄ and R₃₅, which can be identical or different, are hydrogen or C₁-C₁₂alkyl or R₃₄ is additionally a group of the formula (IX) with R₃₅ as defined above, R₃₆ is hydrogen, C₁-C₁₂alkyl, cyclohexyl or benzyl, and x is a number from 2 to 50. The various C₁-C₁₂alkyl substituents are linear or branched and are, for example, methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, iso-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl or dodecyl. The various C₅-C₇cycloalkyl substituents, which are unsubstituted or substituted by C₁-C₄alkyl, in particular methyl, are, for example, cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, trimethylcyclohexyl and preferably cyclohexyl. Examples of C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH are 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl and 4-hydroxybutyl. Examples of C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by C₁-C₈alkoxy are 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 3-butoxypropyl, 3-octoxypropyl and 4-methoxybutyl. Examples of C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by C₂-C₈dialkylamino are 2-diethylaminoethyl, 2-dibutylaminoethyl, 3-dimethylaminopropyl, 3-diethylaminopropyl and 3-dibutylaminopropyl. Representative examples of R₃ and R₄ which, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, which can contain a further heteroatom such as oxygen or nitrogen, are 1-pyrrolidinyl, 1-piperidinyl, 4-morpholinyl, 4-methyl-1-piperazyl and 1-hexahydroazepinyl. Examples of C₂-C₁₂alkylene are ethylene, propylene, trimethylene, tetramethylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene, heptamethylene, octamethylene, trimethylhexamethylene, decamethylene, undecamethylene and dodecamethylene. Examples of C₅-C₁₈cycloalkylene are cyclohexylene or cyclohexylene substituted by C₁-C₄alkyl. Examples of C₈-C₁₈dialkylenecycloalkylene are cyclohexylenedimethylene and dimethylcyclohexylenedimethylene. Examples of C₁₃-C₁₈alkylidenedicyclohexylene are methylenedicyclohexylene and methylene-bis-(dimethylcyclohexylene). An example of C₁₄-C₁₈alkylidenedicyclohexylene is isopropylidenedicyclohexylene. Examples of C₄-C₁₂alkylene interrupted by 1, 2 or 3 oxygen atoms are 3-oxapentane-1,5-diyl, 4-oxaheptane-1,7-diyl, 3,6-dioxaoctane-1,8-diyl-4,9-dioxadodecane-1,12-diyl, 3,6,9-trioxaundecane-1,11-diyl and 4,7,10-trioxatridecane-1,13-diyl. Representative examples of C₄-C₁₂alkylene R₇ interrupted by one, two or three N-R₁₃ groups are 3-methyl-3-azapentane-1,5-diyl, 4-methyl-4-azaheptane-1,7-diyl, 4-butyl-4-azaheptane-1,7-diyl, 4-octyl-4-azaheptane-1,7-diyl, 4-cyclohexyl-4-azaheptane-1,7-diyl, 7-methyl-7-azatridecane-1,13-diyl, 4,7-dimethyl-4,7-diazadecane-1,10-diyl and 3,6,9-triazaundecane-1,11-diyl. Representative examples of C₁₃-C₂₆alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene R₉, which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, are methylenediphenylene, isopropylidenediphenylene, butylidenediphenylene or a group of the formula Preferred examples of C₄-C₆alkylene R₁₅ and R₁₆ interrupted by an N-CH₃ group are 3-methyl-3-azapentane-1,5-diyl, 3-methyl-3-azahexane-1,6-diyl and 4-methyl-4-azaheptane-1,7-diyl. Aliphatic C₂-C₁₂diacyl X₇ and X₁₀ are preferably C₂-C₁₀alkanedioyl, in particular oxalyl, malonyl, succinyl, adipoyl or sebacoyl. The preferred compounds of the formula (III) are those of the formula (IIIa) in which R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, m is an integer from 1 to 4, and, if m is 1, X₂ is Cl or one of the groups -OR₂ and where R₁ is as defined above, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which can be identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl or represents 4-morpholinyl, and, if m is 2, X₂ is one of the groups -O-R₉-O- , where R₆, R₈ and R₁₁, which can be identical or different, are hydrogen, C₁-C₄alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups and R₉ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, isopropylidenedicyclohexylene, phenylene, methylenediphenylene or isopropylidenediphenylene, and, if m is 3, X₂ is a group where R₁₄ and R₁₇, which can be identical or different, are hydrogen, C₁-C₄alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 4, X₂ is a group where R₂₆ and R₂₉, which can be identical or different, are hydrogen, C₁-C₄alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl. If m is 2, other preferred compounds of the formula (III) are those of the formula in which R ' / 3 and R ' / 4 are C₁-C₄alkyl or allyl and R ' / 3 is additionally hydrogen, or the group is 4-morpholinyl. Preferred compounds of the formula (V) are those of the formula (Va) in which R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups, X₄ is one of the groups -OR₂ and where R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₃ and R₄, which can be identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl, or is 4-morpholinyl, w is a number from 2 to 20, the first end group bound to the triazine radical being, for example, ONa, OK or a group X₄ and the second end group bound to the nitrogen atom in the chain being, for example, methyl or a group where A is, for example, ONa, OK or the group X₄ and X₄ is as defined above. Preferred polytriazines containing recurring units of the formulae (VI) and (VII) are those having a molecular weight between 1500 and 10,000 and a (VI):(VII) molar ratio of 3:1 to 1:3, in which X₅ and X₈ are groups of the formula where R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups, X₆ is one of the groups -OR₂ and where R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which can be identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl, or is 4-morpholinyl and X₇ is -(CH₂) 2-6 , -CO(CH₂) y CO- with y being zero to 8, or -CH₂CO-. Those compounds of the formula (VIII) are preferred in which X₁₀ is -(CH₂) 2-6 , -CO(CH₂) z CO- with z being zero to 8, a -CH₂CO- group or a group where X₉ is one of the groups -OR₂ and in which R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and R₃ and R₄, which can be identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl, or is 4-morpholinyl, R₃₄ and R₃₅, which can be identical or different, are hydrogen or methyl, or R₃₄ is a group of the formula (IX) with R₃₅ being hydrogen or methyl, R₃₆ is C₁-C₈alkyl or cyclohexyl and x is a number from 2 to 20. Particularly preferred compounds which contain groups of the formula (II) and which can be prepared in accordance with the present invention are: a) the compounds of the formula (IIIa) in which R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, m is an integer from 1 to 4, and, if m is 1, X₂ is Cl or one of the groups OR₂ and where R₁ is as defined above, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and R₃ and R₄, which can be identical or different, are C₁-C₈alkyl, cyclohexyl or allyl, and R₃ can also be hydrogen, or is 4-morpholinyl, and, if m is 2, X₂ is one of the groups where R₆, R₈ and R₁₁, which can be identical or different, are hydrogen, methyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 3, X₂ is a group where R₁₄ and R₁₇, which can be identical or different, are hydrogen, methyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 4, X₂ is a group where R₂₆ and R₂₉, which can be identical or different, are hydrogen or methyl; and b) the compounds of the formula (Va) in which R₇ is -(CH₂)₂₋₆-, X₄ is one of the groups where R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₃ and R₄, which can be identical or different, are C₁-C₈alkyl or cyclohexyl, and R₃ can also be hydrogen, or is 4-morpholinyl, w is a number from 2 to 10, and the end group bound to the triazine radical is, for example, one of the groups X₄ as defined above and the end group bound to the nitrogen atom in the chain is, for example, methyl or a group with X₄ being as defined above. The process according to the instant invention is especially useful for the preparation of the compounds of Examples 1, 4, 5, 9 and 11 which are shown below. Example 1: Preparation of N,N′-bis-[2,4-bis-[N-(1,2,2,6,6-pentamethyl-4-piperidyl)-butylamino]-1,3,5-triazin-6-yl]-1,6-hexanediamine. a) 84.9 g (0.4 mol) of N-(2,2,6,6-tetramethyl-4-piperidyl)-butylamine are added slowly to a solution of 36.8 g (0.2 mol) of cyanuric chloride in 250 ml of xylene cooled to 10°C, maintaining the temperature between 10° and 15°C. After the end of the addition, the mixture is stirred for 1 hour at ambient temperature, and a solution of 16.8 g (0.42 mol) of sodium hydroxide in 70 ml of water is added. The mixture is heated for 2 hours at 80°C, and 11.6 g (0.1 mol) of 1,6-hexanediamine and 12 g (0.3 mol) of sodium hydroxide are then added. The mixture is then heated for 3 hours under total reflux and subsequently for a further 16 hours while separating off the water of reaction and, finally, 150 ml of water are added, the mixture is stirred for 10 minutes and the aqueous phase is separated off. b) A mixture consisting of 19.8 g (0.43 mol) of formic acid and of a solution obtained by dissolving 13.5 g (0.44 mol) of paraformaldehyde in 24.5 ml of 2 % aqueous NaOH solution is added in the course of about 2 hours to the solution obtained above and heated to 110°C, the water added and the water of reaction simultaneously being separated off azeotropically. The mixture is then cooled to 70-80°C and a solution of 3 g of sodium hydroxide in 20 ml of water is added at 70-80°C. The aqueous layer is separated off and the mixture is dehydrated, separating off the water azeotropically. The solution is then evaporated in vacuo (26 mbar), giving a product of melting point = 110-114°C. Analysis for C₆₈H₁₃₀N₁₆ Calculated: C = 69.70 %; H = 11.18 %; N = 19.12 % Found: C = 69.10 %; H = 11.08 %; N = 18.95 % Examples 2-11: Following the procedure described in Example 1, under the same reaction conditions and using the appropriate reagents, the following compounds of the formula are prepared: Example 12: Following the procedure described in Example 1, under the same reaction conditions and using the appropriate reagents, the compound of the formula of melting point = 224-226°C is prepared. Examples 13-14: Following the procedure described in Example 1, part b), under the same reaction conditions and using the appropriate intermediates, the following compounds containing the recurring unit of the formula are prepared: The molecular weight is determined according to the method described in EP-A-255 990 on pages 18 and 19. Example 15: Preparation of N,N′-bis-[2,4-bis-[N-(1,2,2,6,6-pentamethyl-4-piperidyl)-butylamino]-1,3,5-triazin-6-yl]-N,N′-dimethyl-1,6-hexanediamine. 17.4 g (0.378 mol) of formic acid and 12.97 g (0.432 mol) of paraformaldehyde suspended in 30 ml of water are added to a solution of 6.235 g (0.054 mol) of N,N′-bis-[2,4-bis-[N-(2,2,6,6-tetramethyl-4-piperidyl)-butylamino]-1,3,5-triazin-6-yl]-1,6-hexanediamine, prepared as described in Example 1a, in 90 ml of xylene. The reaction vessel is closed and heated for 7 hours at 130°C. The mixture is then cooled, and a solution of 32 g (0.8 mol) of sodium hydroxide in 70 ml of water is added. The mixture is heated for 1/2 hour at 80°C with stirring. The xylene solution is separated off, washed twice and evaporated in vacuo (2 mbar), giving a product, after drying in an oven, of melting point = 111-114°C. Analysis for C₇₀H₁₃₄N₁₆ Calculated: C = 70.07 %; H = 11.26 %; N = 18.68 % Found: C = 69.94 %; H = 11.26 %; N = 18.62 % Example 16: Preparation of 2-chloro-4,6-bis[N-(1,2,2,6,6-pentamethyl-4-piperidyl)-butylamino]-1,3,5-triazine. 84.9 (0.4 mol) of N-(2,2,6,6-tetramethyl-4-piperidyl)-butylamine are slowly added to a solution of 36.8 g (0.2 mol) of cyanuric chloride in 250 ml of xylene cooled to 10°C, maintaining the temperature between 10° and 15°C. After the end of the addition, the mixture is stirred for 1 hour at room temperature and a solution of 16.8 g (0.42 mol) of sodium hydroxide in 70 ml of water is added. The mixture is heated for 2 hours at 80°C, cooled to room temperature, the aqueous phase being separated off. The organic phase is washed twice with water and then heated to 110°C. A mixture consisting of 21.2 g (0.46 mol) of formic acid and of a solution obtained by dissolving 15.3 g (0.50 mol) of paraformaldehyde in 27.8 ml of 2 % aqueous NaOH solution is added in the course of about 2 hours to the organic solution obtained above and heated to 110°C, the added water and the water of reaction simultaneously being separated off azeotropically. The mixture is then cooled to 70-80°C and a solution of 3.3 g of sodium hydroxyde in 22 ml of water is added at 70-80°C. The aqueous layer is separated off and the mixture is dehydrated, separating off the water azeotropically. The solution is then evaporated in vacuo (26 mbar), giving a product of m.p. = 131-133°C. Analysis for C₃₁H₅₈ClN₇ Calculated Cl = 6.28 % Found Cl = 6.30 %

Claims: A process for the methylation of a compound containing at least one group of the formula (I) by means of a mixture of formaldehyde and formic acid to give the corresponding compound containing at least one group of the formula (II) which comprises effecting the said methylation in an aromatic hydrocarbon solvent, simultaneously separating off the water of reaction and that contained in the reagents by azeotropic distillation, and the molar ratio of the NH groups in the piperidine of the formula (I), formaldehyde and formic acid being 1:1:1 to 1:2:2. A process according to claim 1, wherein the aromatic hydrocarbon solvent is toluene, xylene or trimethylbenzene. A process according to claim 1, wherein the aromatic hydrocarbon solvent is xylene. A process according to claim 1, wherein the molar ratio of the NH groups in the piperidine of the formula (I), formaldehyde and formic acid is 1:1:1 to 1:1.3:1.3. A process according to claim 1, wherein the molar ratio of the NH groups of the piperidine of the formula (I), formaldehyde and formic acid is 1:1:1 to 1:1.2:1.2. A process according to claim 1, wherein the reaction temperature is 80° to 150°C. A process according to claim 1, wherein the reaction temperature is 90° to 130°C. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is of the formula (III) in which X and X₁, which are identical or different, are one of the groups -OR₂ , -SR₂ and where R₁ is hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, phenyl, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, or benzyl, or R₃ and R₄, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, m is an integer from 1 to 6 and, if m is 1, X₂ is as defined above for X and X₁ or is Cl or Br and, if m is 2, X₂ is one of the groups of the formulae (IV)-(IVe) in which R₅ is as defined above for R₁, and R₆, R₈ and R₁₁, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl or are benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, xylylene, C₄-C₁₂alkylene which is interrupted by one, two or three oxygen atoms or N-R₁₃ groups, R₁₃ being C₁-C₁₂alkyl or cyclohexyl, R₉ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, phenylene, C₁₃-C₂₆alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, R₁₀ is hydrogen or methyl, n is an integer from 2 to 6, and, if m is 3, X₂ is one of the groups in which R₁₄, R₁₇, R₁₈, R₁₉, R₂₀, R₂₂, R₂₃ and R₂₅, which are identical or different, are as defined for R₆ and R₈, and R₁₅, R₁₆, R₂₁ and R₂₄, which are identical or different, are C₂-C₁₂alkylene, or R₁₅ and R₁₆ are C₄-C₆alkylene which is interrupted by an N-CH₃ group, r and s, which are identical or different, are integers from 2 to 6 and t is zero or 1, and, if m is 4, 5 or 6, X₂ is a group where R₂₆ and R₂₉, which are identical or different, are as defined for R₆ and R₈, and R₂₇ and R₂₈, which are identical or different, are C₂-C₁₂-alkylene and v is 1, 2 or 3, or, if m is 4, X₂ is additionally one of the groups where R₃₀ and R₃₃, which are identical or different, are as defined above for R₆ and R₈, and R₃₁ and R₃₂, which are identical or different, are C₂-C₁₂alkylene and X is as defined above, or, if m is 6, X₂ is additionally one of the groups where R₃₀, R₃₁, R₃₂ and R₃₃ are as defined above, with the proviso that, in this compound of the formula (III), at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the groups X, X₁ and X₂. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is of the formula (V) in which X₃ is one of the groups of the formulae (IVa), (IVb), (IVc), (IVd) and (IVe) or a group of the formula R₆, R₈, R₁₁, R₁₂, R₁₈, R₁₉ and R₂₀, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl or are benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, xylylene, C₄-C₁₂alkylene which is interrupted by one, two or three oxygen atoms or N-R₁₃ groups, R₁₃ being C₁-C₁₂alkyl or cyclohexyl, R₉ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, phenylene, C₁₃-C₂₆alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, R₁₀ is hydrogen or methyl, n, p, r and s, which are identical or different, are integers from 2 to 6 and q and t are zero or 1, X₄ is one of the groups -OR₂, -SR₂ and where R₁ is hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, phenyl, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, or benzyl, or R₃ and R₄, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, and w is a number from 2 to 50, with the proviso that, in this compound of the formula (V) at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the groups X₃ and X₄. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is a compound containing recurring units of the formulae (VI) and (VII) and having a molecular weight between 1000 and 20,000, in which the (VI):(VII) molar ratio is 4:1 to 1:4, X₅ and X₈, which are identical or different, are one of the groups of the formulae (IVa), (IVb), (IVc), (IVd) and (IVe) or a group of the formula R₆, R₈, R₁₁, R₁₂, R₁₈, R₁₉ and R₂₀, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl or are benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, xylylene, C₄-C₁₂alkylene which is interrupted by one, two or three oxygen atoms or N-R₁₃ groups, R₁₃ being C₁-C₁₂alkyl or cyclohexyl, R₉ is C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, phenylene, C₁₃-C₂₆alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, R₁₀ is hydrogen or methyl, n, p, r and s, which are identical or different, are integers from 2 to 6 and q and t are zero or 1, X₆ is one of the groups -OR₂ , -SR₂ and where R₁ is hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, phenyl, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, or benzyl, or R₃ and R₄, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, X₇ is C₂-C₁₂alkylene, a group aliphatic C₂-C₁₂diacyl, -CH₂CO-, a group -COO-R₉-OOC- with R₉ as defined above, or X₇ is a group with X₉ as defined above for X₆, with the proviso that, in this compound, at least one 1,2,2,6,6-pentamethyl-4-piperidyl group is present in at least one of the radicals X₅, X₆ and X₈. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is of the formula (VIII) in which X₁₀ is C₂-C₁₂alkylene, a group aliphatic C₂-C₁₂diacyl, -CH₂CO-, a group -COO-R₉-OOC- with R₉ being C₂-C₁₂alkylene, C₅-C₁₈cycloalkylene, C₈-C₁₈dialkylenecyclohexylene, C₁₃-C₁₈alkylenedicyclohexylene, C₁₄-C₁₈alkylidenedicyclohexylene, phenylene, C₁₃-C₂₆-alkylenediphenylene or C₁₄-C₂₆alkylidenediphenylene which is unsubstituted or substituted on the benzene ring by C₁-C₄alkyl, or X₁₀ is a group where X₉ is one of the groups -OR₂ , -SR₂ and where R₁ is hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, phenyl, benzyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₁₂alkyl, C₅-C₇cycloalkyl which is unsubstituted or substituted by C₁-C₄alkyl, allyl, C₂-C₄alkyl monosubstituted in the 2-, 3- or 4-position by OH, C₁-C₈alkoxy or C₂-C₈dialkylamino, or benzyl, or R₃ and R₄, together with the nitrogen atom to which they are linked, form part of a 5-membered to 7-membered heterocyclic ring, R₃₄ and R₃₅, which are identical or different, are hydrogen or C₁-C₁₂alkyl or R₃₄ is additionally a group of the formula (IX) with R₃₅ as defined above, R₃₆ is hydrogen, C₁-C₁₂alkyl, cyclohexyl or benzyl, and x is a number from 2 to 50. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is of the formula (IIIa) in which R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, m is an integer from 1 to 4, and, if m is 1, X₂ is Cl or one of the groups -OR₂ and where R₁ is as defined above, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl or represents 4-morpholinyl, and, if m is 2, X₂ is one of the groups -O-R₉-O- , where R₆, R₈ and R₁₁, which are identical or different, are hydrogen, C₁-C₄alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups and R₉ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, isopropylidenedicyclohexylene, phenylene, methylenediphenylene or isopropylidenediphenylene, and, if m is 3, X₂ is a group where R₁₄ and R₁₇, which are identical or different, are hydrogen, C₁-C₄alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 4, X₂ is a group where R₂₆ and R₂₉, which are identical or different, are hydrogen, C₁-C₄alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl. A process according to claim 1, wherein the compound containing at least one group of the formula (II) is of the formula (Va) in which R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups, X₄ is one of the groups -OR₂ and where R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₃ and R₄, which are identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl, or is 4-morpholinyl and w is a number from 2 to 20. A process according to claim 10, wherein the compound containing at least one group of the formula (II) is a compound containing recurring units of the formulae (VI) and (VII), and having a molecular weight between 1500 and 10,000 and a (VI):(VII) molar ratio of 3:1 to 1:3, in which X₅ and X₈ are groups of the formula where R₇ is C₂-C₆alkylene, cyclohexylene, cyclohexylenedimethylene, methylenedicyclohexylene or C₄-C₁₂alkylene which is interrupted by one or two oxygen atoms or N-CH₃ groups, X₆ is one of the groups -OR₂ and where R₁ is C₁-C₈alkyl, cyclohexyl, 1,2,2,6,6-pentamethyl-4-piperidyl or C₂-C₃alkyl monosubstituted in the 2- or 3-position by OH, C₁-C₄alkoxy or C₂-C₄dialkylamino, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₈-alkyl, cyclohexyl or allyl, or is 4-morpholinyl and X₇ is -(CH₂) 2-6 , -CO(CH₂) y CO- with y being zero to 8, or a -CH₂CO- group. A process according to claim 11, wherein the compound containing at least one group of the formula (II) is of the formula (VIII) in which X₁₀ is -(CH₂) 2-6 , -CO(CH₂) z CO- with z being zero to 8, a -CH₂CO- group or a group where X₉ is one of the groups -OR₂ and in which R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and R₃ and R₄, which are identical or different, are hydrogen, C₁-C₈alkyl, cyclohexyl or allyl, or is 4-morpholinyl, R₃₄ and R₃₅, which are identical or different, are hydrogen or methyl, or R₃₄ is a group of the formula (IX) with R₃₅ being hydrogen or methyl, R₃₆ is C₁-C₈alkyl or cyclohexyl and x is a number from 2 to 20. A process according to claim 12, wherein the compound containing at least one group of the formula (II) is of the formula (IIIa) in which R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, m is an integer from 1 to 4, and, if m is 1, X₂ is Cl or one of the groups -OR₂ and where R₁ is as defined above, R₂ is C₁-C₈alkyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and R₃ and R₄, which are identical or different, are C₁-C₈alkyl, cyclohexyl or allyl, and R₃ is additionally hydrogen, or is 4-morpholinyl, and, if m is 2, X₂ is one of the groups where R₆, R₈ and R₁₁, which are identical or different, are hydrogen, methyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 3, X₂ is a group where R₁₄ and R₁₇, which are identical or different, are hydrogen, methyl or 1,2,2,6,6-pentamethyl-4-piperidyl, and, if m is 4, X₂ is a group where R₂₆ and R₂₉, which are identical or different, are hydrogen or methyl. A process according to claim 13 wherein the compound containing at least one group of the formula (II) is of the formula (Va) in which R₇ is -(CH₂)₂₋₆-, X₄ is one of the groups where R₁ is C₁-C₈alkyl, cyclohexyl or 1,2,2,6,6-pentamethyl-4-piperidyl, R₃ and R₄, which are identical or different, are C₁-C₈alkyl or cyclohexyl, and R₃ is additionally hydrogen, or is 4-morpholinyl, and w is a number from 2 to 10.

Inventors: BORZATTA VALERIO DR, HOLER MARTIN, ORBAN IVAN DR, PICCINELLI PIERO, BORZATTA, VALERIO, DR., HOLER, MARTIN, ORBAN, IVAN, DR., PICCINELLI, PIERO
Applicants: CIBA GEIGY AG, CIBA GEIGY SPA, CIBA-GEIGY AG, CIBA-GEIGY S.P.A.
Application year: 1988
Main classification: C07D401
IPC codes: C07D401