摘要:
An improved process for the preparation of riboflavin by condensation of a 4,5-dimethyl-N-(D)-ribityl-2-phenylazoaniline derivative with barbituric acid in the presence of an acidic condensing agent in an organic solvent, wherein a 4,5-dimethyl-N-(D)-ribityl-2-(o-alkoxyphenylazo)-aniline of the formula IIa ##STR1## where R is alkyl of 1 to 4 carbon atoms, in particular methyl, is reacted with barbituric acid, as well as the novel intermediates of the formula IIa.
摘要:
A process for the preparation of 1,1,4,4-tetramethoxy-2-butene by reacting 2,5-dimethoxydihydrofuran with methanol in the presence of acids comprises carrying out the reaction in the presence of solid catalysts having acidic centers.
摘要:
(2R,6R)-1-Chloro-2,6,10-trimethyl-undecane I, (R)-(+)-.beta.-chloro-isobutyric acid II, (S)-(+)-1-bromo-3-chloro-2-methylpropane IV and (2R)-(+)-1-chloro-2,6-dimethyl-heptane V are novel optically active units for the synthesis of the side chain of (R,R,R)-.alpha.-tocopherol. In the process according to the invention, the optically active C.sub.14 -chloride I is obtained in 6 simple reaction steps starting from II, via the novel intermediates IV and V, in accordance with the following equation: ##STR1##
摘要:
Improved process for the preparation of astaxanthin by Wittig reaction of 2 mol of 3-methyl-5-(2,6,6-trimethyl-3-oxo-4-hydroxy-1-cyclohexenyl)-2,4-pentadienyltriarylphosphonium salts with one mol of 2,7-dimethyl-2,4,6-octatrienedial avoiding the use of halohydrocarbons as solvents.
摘要:
A process for preparing canthaxanthin (Ia) and astaxanthin (Ib) of the formula I ##STR1##where R is H (a) or OH (b), comprises reacting a tertiary alcohol of the formula II ##STR2##where R is H (a) or OH (b), with trifluoroacetic acid, reacting the resulting novel trifluoroacetate of the formula III ##STR3##with triphenylphosphine, and reacting the resulting novel triphenylphosphonium trifluoroacetate of the formula IV ##STR4## with 2,7-dimethyl-2,4,6-octatriene-1,8-dial under the conditions of a Wittig synthesis. The present invention also relates to the novel trifluoroacetates of the formula III and the corresponding triphenylphosphonium trifluoroacetates of the formula IV.
摘要:
In an improved process for the preparation of 2-n-propyl-4-amino-5-methoxymethyl-pyrimidine of the formula I ##STR1## by reacting butyramidine II ##STR2## with .alpha.-methoxymethyl-.beta.-methoxyacrylonitrile III ##STR3## the butyramidine II is reacted with a 0.4-5 molar excess of .alpha.-methoxymethyl-.beta.-methoxyacrylonitrile III at from -10.degree. to +20.degree. C.
摘要:
Pentoses and hexoses are epimerized by heating sugar dissolved in a solvent in the presence of a molybdenum(VI) compound, by an improved process in which, for the preparation of a sugar having cis OH groups in the 2- or 3-position, of the formula Ia or Ib ##STR1## where R is one of the radicals ##STR2## a homogeneous solution of the corresponding sugar of the formula IIa or IIb ##STR3## is heated to 75.degree.-100.degree. C. in the presence of from 30 to 200 mol %, based on sugar used, of a metal salt of the formula (III)MeX.sub.2 (III)where Me is Mg, Ca, Sr, Ba or Zn and X is Cl or Br, which may or may not contain water of crystallization, and in the presence of from 2 to 20 mol %, based on the sugar used, of a molybdenum(VI) compound.The process is particularly important for the preparation of D-ribose, which is required as an intermediate for vitamin B.sub.2.
摘要:
A process for the preparation of .alpha.-tocopherol of the formula I ##STR1## by reacting a chroman derivative with a C.sub.14 -Grignard reagent using a di-alkali metal tetrahalocuprate catalyst in a Schlosser-Fouquet reaction, wherein a chroman derivative of the general formula II ##STR2## where Y is a leaving group, especially Br, is used and is reacted, at from -70.degree. to 0.degree. C., first with a solution of about 1 equivalent of a Grignard compound of the general formula IIIX--Mg--R (III)where X is Cl, Br or I and R is straight-chain or branched alkyl of 1 to 14 carbon atoms, preferably methyl, ethyl or ##STR3## and then with a solution of a Grignard reagent of the formula IIIa ##STR4## in an ether solvent and a solution of a di-alkali metal tetrahalocuprate in an ether solvent. The novel process simplifies the preparation of 2RS,4'RS,8'RS-, 2R,4'RS,8'RS- or 2R,4'R,8'R-.alpha.-tocopherol by reacting a chroman structural unit, containing a C.sub.2 side-chain in the 2-position, with the corresponding C.sub.14 -Grignard compound.
摘要:
Riboflavin of the formula I ##STR1## is prepared by condensing a 4,5-dimethyl-N-(D)-ribityl-2-phenylazoaniline of the formula II ##STR2## where R is H or --Cl, --NO.sub.2 or --CH.sub.3 in the o- or p-position, with barbituric acid of the formula III ##STR3## in the presence of an acid as the condensing agent, by an improved process in which the acidic condensing agent used is an aliphatic or cycloaliphatic/aliphatic tertiary carboxylic acid of the general formula IV ##STR4## where R.sup.1, R.sup.2 and R.sup.3 are each a lower alkyl group, R.sup.1, R.sup.2 and R.sup.3 together containing 3 to 20, preferably 3 to 10, carbon atoms, or R.sup.1 is a lower alkyl group, in particular methyl, and R.sup.2 and R.sup.3 together form a tetramethylene or pentamethylene group.The process can be particularly advantageously carried out using trimethylacetic acid or a commercial mixture of saturated tertiary carboxylic acids, e.g. Versatic .sup.R 10-acid.
摘要:
A process for preparing polyenecarbonyl compounds having a high all-E content and their acetals or ketals by aldol condensation or Horner-Emmons reaction comprises carrying out the reaction, for the purposes of the preferred formation of a double bond of E configuration and in order to maintain the E configuration of the double bonds in the stating compounds as completely as possible, in the presence of oxygen or an oxygen-inert gas mixture or nitric oxide or a nitric oxide-inert gas mixture and/or in the presence of specific stable radicals and/or in the presence of quinones or quinone derivatives.