Abstract: Preparation of mixtures of O-phenoxyalkylhydroxylamines Ia and Ib ##STR1## and the corresponding salt mixtures by a) converting mixtures of isomers of O-(2-hydroxyethyl)oximes IIa and IIb ##STR2## with a sulfonyl halide III ##STR3## into a mixture of sulfonates IVa and IVb ##STR4## b) reacting this mixture of IVa and IVb with a phenol HO-Ar (V) to give a mixture of O-phenoxyalkoximes VIa and VIb ##STR5## c) hydrolyzing this mixture in the presence of an acid and, if desired d) liberating the O-phenoxyalkylhydroxylamines Ia and Ib from the resulting salts using a mineral acid.Compounds Ia/Ib and VIa/VIb are important intermediates for crop protection agents.

Abstract: Diphenylheteroalkyl derivatives of the formula I ##STR1## where A and R.sup.1 -R.sup.6 have the meanings specified in the description, and the preparation thereof are described.The substances are suitable for controlling diseases and as cosmetic agents.

Abstract: Compositions and processes to alleviate free radical toxicity are disclosed based on the use of nitroxides in association with physiologically compatible macromolecules. In particular, hemoglobin-based red cell substitutes are described featuring stable nitroxide free radicals for use in cell-free hemoglobin solutions, encapsulated hemoglobin solutions, stabilized hemoglobin solutions, polymerized hemoglobin solutions, conjugated hemoglobin solutions, nitroxide-labelled albumin, and nitroxide-labelled immunoglobulin. Formulations are described herein that interact with free radicals, acting as antioxidant enzymemimics, which preserve nitroxides in their active form in vivo. Applications are described including blood substitutes, radioprotective agents, imaging agents, agents to protect against ischemia and reperfusion injury, and in vivo enzyme mimics among others.

Abstract: Substituted hydroxylamine antioxidants can be prepared by reacting hydroxylamine or a mono-substituted hydroxylamine with an epoxide. The antioxidant reaction product is not removed from the reaction mixture, but is used without separation after combination with a color developer to provide a photographic color developer composition. The antioxidants are highly water soluble and thus exhibit no objectionable odor.

Abstract: Disclosed is a process for producing a 4-nitrosodiphenylamine of the formula (2) ##STR1## wherein R.sub.1 and R.sub.2 independently represent hydrogen atom, methyl group, ethyl group, cyclohexyl group, methoxy group, ethoxy group or chlorine or bromine atom, or a salt thereof, comprising treating a diphenylamine represented by the formula (1) ##STR2## wherein R.sub.1 and R.sub.2 are as defined above with (i) a mixture of nitrogen oxides, (ii) a hydrogen halide and (iii) an aliphatic alcohol, wherein the atomic ratio of oxygen to nitrogen of the mixture of nitrogen oxides is more than 1.0 and less than 2.0. This process produces 4-nitrosodiphenylamine of the formula (2) or a salt thereof conveniently and effectively, and is industrially advantageous.

Abstract: Acaricidal, insecticidal and nematicidal substituted (hetero)arylalkyl ketone oxime O-ethers, processes for their preparation, agents containing them, and their use as pesticides.The invention relates to compounds of the formula ##STR1## in which Ar.sup.1 and Ar.sup.2 are aryl or heteroaryl, each of which is optionally substituted, and R is an optionally substituted aliphatic or alicyclic radical, to processes for their preparation, and to agents containing these compounds, and to their use for controlling animal pests.

Abstract: Substituted hydroxylamine antioxidants can be prepared by reacting hydroxylamine or a mono-substituted hydroxylamine with an epoxide. The antioxidant reaction product is not removed from the reaction mixture, but is used without separation after combination with a color developer to provide a photographic color developer composition. The antioxidants are highly water soluble and thus exhibit no objectionable odor.

Abstract: This invention relates to a 1,2-ethanediol derivative and a salt thereof, a process for producing the same, and a cerebral function-improving agent comprising the same. The cerebral function-improving agent of this invention is useful for treating cerebrovascular dementia, senile dementia, Alzheimer's dementia, sequelae of ischemic encephalopathy and cerebral apoplexy.

Abstract: Preparation of O-substituted hydroxylammonium salts IR.sup.1 --CHX--O--NH.sub.2.HL (I)(L=halogen, hydrogensulfate; X=H, alkyl; R.sup.1 =unsubst. or subst. phenyl, thienyl, furanyl, pyrrolyl or --CR.sup.2 .dbd.CR.sup.3 R.sup.4 ; R.sup.2, R.sup.3, R.sup.4 =H, halogen or alkyl) by reaction of an acetone oxime O-allyl or --O--benzyl ether II ##STR1## with water and a mineral acid H--L with continuous removal of the acetone formed in this process, by carrying out the hydrolysis batchwise at 0.degree.-50.degree. C. and under a pressure of 10-500 mbar is described.The O-substituted hydroxylammonium salts I are intermediates for plant protection agents and pharmaceuticals.

Abstract: A catalytically active gel is described consisting of a silica matrix with uniform porosity, monomodal pore distribution and high surface area, within which one or metal oxides possessing catalytic activity are dispersed. A process for preparing this catalytic gel is also described.

Abstract: The invention is the use of nitronyl substituted hindered phenols as antioxidants in therapeutic applications. In the preferred embodiment the compositions have the general formula: ##STR1## Wherein R1 is hydrogen, an alkyl or an aryl and R2 is an alkyl or an aryl; R.sub.3 is an alkyl; and R.sub.4 is an alkyl. Further, the invention relates to novel compositions useful as antioxidants. The novel compounds include: 2,6-di-tert-butyl-4-(N-tert-octyl) nitronyl phenol (DBONP); 2,6-dimethyl-4-(N-tert-octyl) nitronyl phenol (DMONP); N-tert -octylC-phenyl nitrone (OPN).

Abstract: The invention is the use of nitronyl substituted hindered phenols as antioxidants in therapeutic applications. In the preferred embodiment the compositions have the general formula: ##STR1## Wherein R1 is hydrogen, an alkyl or an aryl and R2 is an alkyl or an aryl; R.sub.3 is an alkyl; and R.sub.4 is an alkyl. Further, the invention relates to novel compositions useful as antioxidants. The novel compounds include: 2,6-di-tert-butyl-4-(N-tert-octyl) nitronyl phenol (DBONP); 2,6-dimethyl-4-(N-tert-octyl) nitronyl phenol (DMONP); N-tert-octylC-phenyl nitrone (OPN).

Abstract: Compounds of formula (I): H.sub.2 N--(CH.sub.2).sub.n --A--(CH.sub.2).sub.m --O--NH.sub.2 and salts thereof are described in which the radical A is C.sub.3 -C.sub.6 cycloalkylene; n is 0 or 1 and, independently thereof, m is 0 or 1; with the provisos that a) the distance between the aminooxy radical H.sub.2 N--O-- and the amino group --NH.sub.2 is at least 3 and not more than 4 carbon atoms and that b) the two radicals H.sub.2 N--(CH.sub.2).sub.n -- and --(CH.sub.2).sub.m --O--NH.sub.2 are not bonded to the same ring carbon of A. The compounds of formula (I) and their salts are ornithine decarboxylase inhibitors.

Abstract: The present invention relates to a process for the preparation of compounds of the general formula I ##STR1## by reaction of compounds of the general formula II ##STR2## with compounds of the general formula III ##STR3## in inert aprotic solvents in the presence of a base and subsequent rearrangement of the resulting intermediate compound with an alkali metal hydroxide, characterized in that the intermediate compound is not isolated.

Abstract: This invention relates to a 1,2-ethanediol derivative and a salt thereof, a process for producing the same, and a cerebral function-improving agent comprising the same. The cerebral function-improving agent of this invention is useful for treating cerebrovascular dementia, senile dementia, Alzheimer's dementia, sequelae of ischemic encephalopathy and cerebral apoplexy.

Abstract: The invention is the use of nitronyl substituted hindered phenols as antioxidants in therapeutic applications. In the preferred embodiment the compositions have the general formula: ##STR1## Wherein R1 is hydrogen, an alkyl or an aryl and R2 is an alkyl or an aryl; R.sub.3 is an alkyl; and R.sub.4 is an alkyl. Further, the invention relates to novel compositions useful as antioxidants. The novel compounds include: 2,6-di-tert-butyl-4-(N-tert-octyl)nitronyl phenol (DBONP); 2,6-dimethyl-4-(N-tert-octyl)nitronyl phenol (DMONP); N-tert-octyl-C-phenyl nitrone (OPN).

Abstract: Oxidation of primary amines to primary hydroxylamines using a dialkyl dioxirane is described. This new method is utilized to prepare aliphatic non-axial hydroxylamines from corresponding primary amino-substituted sugar derivatives and hydroxylamino acid derivatives.

Abstract: The present invention relates to a composition comprising an antimicrobial effective amount of a biocide selected from the group consisting of aromatic 2-N-hydroxy-thiourea and N-hydroxy-quinazolinone, and derivatives and combinations thereof, and at least one component selected from the group consisting of soaps, shampoos, skin-care medicaments, cosmetics, plastics and paints. Also disclosed is a novel process for making the biocide.

Abstract: Reaction of amine-containing substrates with hydrogen peroxide can suffer from certain problems, especially in the presence of transition metals. These problems include both in situ generation of impurities and particularly nitrosamines, which are allegedly carcinogenic, and also impaired product formation. The problems can be ameliorated by employing in the reaction mixture free radical scavengers, including in particular phenols and polyhydroxy-substituted aromatic compounds. The scavengers are advantageously employed in conjunction with a metal chelating agent such as polycarboxylic acid or an organopolyphosphonic acid.

Abstract: A process for treating solutions of a hydroxylammonium salt containing excess acid which comprises:a) mixing the hydroxylammonium salt containing excess acid with a hydroxylammonium solution containing free hydroxylamine to produce a solution of the hydroxylammonium salt substantially free of excess acid,b) contacting a portion of the solution of the hydroxylammonium salt substantially free of excess acid with a weak base ion exchange resin to produce the hydroxylammonium solution containing free hydroxylamine, and,c) recycling the hydroxylammonium solution containing free hydroxylamine to step a).The process minimizes the decomposition of the hydroxylammonium salt solution and produces high purity hydroxylammonium nitrate solutions without directly contacting excess nitric acid with ion exchange resins. In addition to hydroxylammonium salts, the process can be used to treat any nitrate salt of an anine weak base which contains excess nitric acid.

Abstract: Antibacterial compounds of the formula ##STR1## wherein R is a mononuclear carbocyclic aromatic group, a 5-membered aromatic heterocyclic group which contains as the hereto (non-carbon) ring member(s) an oxygen or sulphur atom or an imino or lower alkylimino group and, optionally, one or two nitrogen atoms, or a 6-membered aromatic heterocyclic group which contains one to three nitrogen atoms as the hereto ring member(s); R.sup.1 is hydrogen or a 3-substituent which is usable in cephalosporin chemistry; A is lower alkylene or C.sub.3-7 -cycloalkylene which is optionally substituted with carboxy, carbamoyl, lower alkylcarbamoyl or di(lower alkyl)carbamoyl; Q is lower alkylene or C.sub.3-7 -cycloalkylene which is optionally substituted with carboxy, carbamoyl, lower alkylcarbamoyl or di(lower alkyl)carbamoyl or the group --NR.sup.2 -- or --NR.sup.2 NR.sup.3 --; R.sup.2 and R.sup.3 are independently hydrogen or lower alkyl; p and m are the zero or 1, n is zero, 1 or 2; R.sup.

Abstract: A novel herbicidal pyrimidine derivative represented by the formula ##STR1## wherein each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, Y.sup.1, Y.sup.2, Y.sup.3, X and Z are as defined herein.

Abstract: Catalytic hydrogenation of nitroalkane to N-alkylhydroxylamine free base in the absence of transition metal ions, and omission of acid and the resultant free base is storage stable, permitting shipment and storage of 15% aqueous solution for use as oxygen scavenger in boiler feed water treatment.

Abstract: 1-Alkoxy-1,3-diazacycloalkane derivatives of the formula I ##STR1## where: n is 0 or 1;R.sup.1 is substituted or unsubstituted alkyl, alkylcarbonyl, cycloalkylcarbonyl, alkenyl or alkynyl, a substituted or unsubstituted heterocyclic radical or a group --C(.dbd.O)--R, where R is substituted or unsubstituted phenyl or a substituted or unsubstituted aliphatic or aromatic heterocyclic structure,X ishydrogen; halogen; alkoxy; alkylthio; alkylcarbonyl; haloalkylcarbonyl; alkoxycarbonyl;substituted or unsubstituted alkyl, phenyl, phenoxy, phenylthio, benzoyl or phenyloxycarbonyl; andR.sup.2 ishydrogen or alkyl,processes and intermediates for their manufacture, and their use in pesticides.

Abstract: There is provided a process for producing sulfoalkyl-substituted hydroxylamines useful as preservatives to be added to a color developer for photosensitive materials. In this process, the sulfoalkyl-substituted hydroxylamines can be easily synthesized by reacting a specified alkylating agent, cyclic sulfonic ester, vinylsulfonic acid or sulfoalkylsubstituted acrylamide with a hydroxylamine.

Abstract: A process is disclosed for the enantioselective hydrogenation of olefins of the formula ##STR1## where R is hydrogen or C.sub.1 to C.sub.6 linear or branched alkyl, Z is ##STR2## where R' is hydrogen or C.sub.1 to C.sub.6 linear or branched alkyl, --CN, C(NH)OR" where R" is C.sub.1 to C.sub.6 linear or branched alkyl, or --C(O)NH.sub.2 ; and Ar is phenyl or naphthyl unsubstituted or substituted with benzoyl or substituted benzoyl, C.sub.1 to C.sub.6 linear or branched alkyl, C.sub.1 to C.sub.6 linear or branched alkoxy, halo, or carboxylic acid or C.sub.1 to C.sub.6 linear or branched alkyl ester thereof, which comprises contacting said aromatic-substituted olefin with a catalytically effective amount of a ruthenium phosphite complex.

Abstract: The present invention relates to a process for the preparation of organic hydroxylamines as a result of the corresponding nitroderivative being hydrogenated in the presence of an inert solvent, a platinum catalyst, a nitrogen-containing base (in an amount of less than 10% by weight calculated on the amount of nitro derivative) and a tri- or pentavalent organic phosphorus compound. It has been found that if only use is made of the nitrogen-containing base or the phosphorus compound the yields of isolated hydroxyl amine are significantly reduced in comparison with those obtained with the present process.

Abstract: Herbicidal 3-hydroxy-2-cyclohexen-1-ones of the formula ##STR1## wherein R.sup.1 and R.sup.2 each is hydrogen or methyl,R.sup.3 is C.sub.1-4 alkyl, cyclopropylmethyl, C.sub.3-4 alkenyl which may be substituted by one to three halogen atoms or C.sub.3-4 alkynyl,R.sup.4 is C.sub.1-4 alkyl,R.sup.5 each independently is halogen, C.sub.1-4 alkyl, C.sub.1-4 haloalkyl, C.sub.1-4 alkoxy, C.sub.1-4 haloalkoxy, C.sub.1-4 alkylthio, C.sub.1-4 haloalkylthio or cyano,n is 0, 1 or 2, andm is 0, 1 or 2.

Abstract: Symmetrically substituted N,N-dihydrocarbylhydroxylamines are prepared in a single step by the reaction of an aldehyde and hydroxylamine hydrochloride in an alcoholic solvent in the presence of hydrogen and a hydrogenation catalyst. The free N,N-dihydrocarbylhydroxylamine is liberated from the hydrochloride salt by treatment with alkali. N,N-dihydrocarbylhydroxylamines, particularly the N,N-dialkylhydroxylamines, are useful stabilizers for a variety of polymers.

Abstract: O-substituted hydroxylamines (I)H.sub.2 N--O--CH.sub.2 --R(I)where R is H or an organic radical, and their salts are prepared by reacting a cyclic imidoether II of a 1,4- or 1,5-dicarboxylic acid, the said imidoether containing an ether group --O--CH.sub.2 --R, with a basic compound by a method in which a primary aliphatic aminoalcohol III is used as the basic compound and the compound I is, if required, converted to its salts.

Abstract: The present invention relates to vinylogous hydroxamic acids, processes for their manufacture, pharmaceutical preparations containing them, and their use in the treatment of various disorders.

Abstract: Hydroxylamine derivatives have the general formula IAryl--A--O--B IwhereAryl is an unsubstituted or substituted, mononuclear or binuclear, isocyclic radical;A is a 1,4-butenylene group of the general formulae IIa or IIb ##STR1## where R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are each hydrogen, halogen, C.sub.1 -C.sub.6 -alkyl or C.sub.1 -C.sub.6 -alkenyl;B is NH.sub.2 or a dicarboximide group of the general formula III ##STR2## where Z is unsubstituted or substituted phenylene, naphthylene, pyridinylene, cyclopentylene, cyclohexylene, cyclohexenylene, C.sub.2 -C.sub.4 -alkenylene or C.sub.2 -C.sub.4 -alkylene. The dicarboximides are intermediates for the compounds wherein B is NH.sub.2. The latter are used in synthesizing herbicidal compounds.

Abstract: O-substituted hydroxylamines of the formula IH.sub.2 NOR.sub.1 (I)in whichR.sub.1 is C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 haloalkyl, --CH.sub.2 CR.sub.2 .dbd.CR.sub.3 R.sub.4 or --CH.sub.2 C.tbd.CR.sub.5 ;R.sub.2 is hydrogen, halogen or methyl;R.sub.3 is hydrogen, halogen or methyl;lR.sub.4 is hydrogen, halogen or methyl; andR.sub.5 is hydrogen, methyl or ethyl,R.sub.6 --CN (II)in which R.sub.6 is C.sub.1 -C.sub.4 alkyl, phenyl or benzyl, is reacted with an alcohol of the formula IIIR.sub.7 --OH (III)in which R.sub.7 is C.sub.1 -C.sub.5 alkyl, benzyl or C.sub.1 -C.sub.4 alkoxyethyl, in an organic solvent which is only sparingly miscible with water or not at all, in the presence of hydrogen halide HX, the suspension obtained of the iminoester hydrohalide of the formula IV ##STR1## in which R.sub.6 and R.sub.7 are as defined above and X is chlorine, bromine or iodine, is added at a controlled rate to an aqueous suspension of a carbonate or hydrogen carbonate at a temperature of from -3.degree. to +5.degree.

Abstract: Substituted amino carbamate derivatives corresponding to the formula ##STR1## are effective in stabilizing organic materials against oxidative, thermal and actinic degradation, said derivatives being particularly effective as color improvers and process stabilizers in organic materials containing phenolic antioxidants and/or metal salts of fatty acids and/or hindered amine light stabilizers and/or organic phosphorus compounds; and certain of said derivatives as new compounds.

Abstract: O-Alkenyl substituted hydroxylamines of formula I ##STR1## where R.sub.1 and R.sub.2 are independently hydrogen, alkyl, alkenyl, aryl or phenylalkyl, and R.sub.3 to R.sub.7 are independently hydrogen, alkyl or substituted alkyl are very effective process stabilizers for polymeric systems providing melt flow stabilization and resistance to discoloration during processing at elevated temperatures as well as effective stabilizers for lubricant compositions.

Abstract: There are disclosed intermediate compounds of the formula, ##STR1## wherein the substitutents of R.sub.1 to R.sub.7 and R.sub.9 have the same meanings as described in the text, for producing a insecticidal and acaricidal pyrazole compound represented by the formula, ##STR2## wherein the substituents of R.sub.1 ' to R.sub.8 and the symbol Z have the specified meanings as described in the text.

Abstract: There are disclosed a pyrazole compound represented by the formula ##STR1## wherein the substituents of R.sub.1 to R.sub.7 and the symbol Z have the specified meanings as described in the text, an insecticidal, acaricidal and fungicidal composition containing the same, use of said composition for control of insects, acarids and fungi and a method of preparing said compound, and its intermediate.

Abstract: Reaction of amine-containing substrates with hydrogen peroxide can suffer from the problems of in situ generation of nitrosamines, which are allegedly carcinogens, as impurities and impaired product formation, especially in the presence of transition metals.The problems can be ameliorated by employing a selected range of alkyleneaminopoly(methylenephosphonic acid) compounds such as cyclohexane-1,2-diaminotetra(methylenephosphonic acid).

Abstract: N,N-Dialkylhydroxylamines where the alkyl groups are of 10 to 30 carbon atoms are prepared by an improved process involving the direct oxidation of the corresponding N,N-dialkylamines with aqueous hydrogen peroxide in a lower alkanol solvent in the absence of a catalyst or a sequestering agent.The improved process prevents the problem of over-oxidation and gives the desired N,N-dialkylhydroxylamine in high yield and purity. The N,N-dialkylhydroxylamines are effective stabilizers for polymer compositions particularly as process stabilizers for polyolefins.

Abstract: There is provided a method for the production of hydroxylamine derivatives or the salt thereof in which a salt of hydroxamic acid is reacted with an alkylating agent such as diethyl sulfate to form an ester of hydroxamic acid, which is reacted with mineral acid in an aqueous solution of lower alcohol so as to prepare hydroxylamine derivatives or the salt thereof. In this process, the incorporation of an oxidizing agent or aldehydes in the reaction system will significantly reduce the content of nitrosoamines in the resulting solution of hydroxylamine derivatives or the salt thereof. Therefore, the resulting hydroxylamine derivatives obtained with a lesser content of harmful compound will be useful as an intermediate for the production of drugs and pesticides.

Abstract: The subject invention relates to a method of synthesizing hydroxylamines from secondary amines. This method uses a dioxirane compound such as dimethyldioxirane (DMD, which is relatively stable and simple to synthesize), as the oxidizing agent. The reaction proceeds as follows: ##STR1## This method provides a simple, one-step reaction with high yields. It can be performed in acetone solution, and the transferral of an oxygen atom from dimethyldioxirane to the secondary amine converts the dioxirane into acetone, the solvent, permitting simple workup and purification. This method can be used with a wide variety of secondary amines, including aliphatic, aromatic, cyclic, and heterocyclic secondary amines, to create a corresponding variety of hydroxylamines.

Abstract: Tert-amine oxides that are substantially free of nitrosamines are made by reacting a tert-amine, e.g., dodecyl dimethylamine, with aqueous hydrogen peroxide in the presence of the synergistic combination of (a) ascorbic acid and (b) a promoter formed from carbon dioxide.

Abstract: Substituted hydroxylamine ester stabilizers corresponding to the formula ##STR1## wherein n is 0-2, X is a direct bond, --S-- or --CH.sub.2 S--, R.sub.1 and R.sub.2 are independently hydrogen, alkyl, cycloalkyl, aralkyl, R.sub.3 and R.sub.4 are independently alkyl, cycloalkyl or aralkyl, and R.sub.5 is hydrogen or the group ##STR2## are effective in stabilizing organic materials against oxidative, thermal and actinic degradation.

Abstract: A new method for the production of O-substituted hydroxylamines is disclosed. Hydroxylamine-O-sulfonic acid is reacted with alkali alkoxide in the presence of a polar aprotic solvent.

Abstract: The present invention includes N-hydroxyamide, N-hydroxyurea, N-hydroxythioamide, and N-hydroxythiourea derivatives of fenamates, indomethacin, cicloprofen, oxepinac, and indoprofen as dual inhibitors or selective inhibitors of cyclooxygenase and 5-lipoxygenase.

Abstract: An agent for preventing vinyl chloride polymer build-up, which contains as the effective ingredient a reaction product of ammonium salt or a metal salt of N-nitrosophenylhydroxylamine with an aldehyde.

Abstract: Compounds of the formula ##STR1## wherein X is a hydrogen atom, a halogen atom, a trihalomethyl group, or an alkyl group,Y is a hydrogen atom or a halogen atom,R.sup.1 is a hydrogen atom, a hydroxy group, an alkoxy group, or an optionally-substituted-alkyl group, andR.sup.2 is a hydrogen atom or an optionally substituted alkyl group, or R.sup.1 and R.sup.2 can be taken together to form a heterocyclic ring,and compositions containing these compounds exhibit herbicidal activity.

Abstract: A process for preparing a stable 4-hydroxyacetophenone oil by mixing 4-hydroxyacetophenone with an aqueous hydroxylamine salt in the absence of added caustic, at a temperature of 50.degree.-100.degree. C., for about 10-60 minutes and then cooling the same is disclosed.

Abstract: Compounds of the formulae ##STR1## are useful stabilizers of organic polymeric materials which are subject to thermal, oxidative and/or actinic degradation.

Abstract: The invention relates to a process for the synthesis of an N,N-dialkyl-hydroxylamine by reaction of the corresponding dialkylamine with H.sub.2 O.sub.2, said reaction being carried out in the presence of a catalyst based on titanium-silicalite.