Abstract: 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.

Abstract: Novel optically active chroman derivatives of the general formulae Ia and Ib ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.

Abstract: 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.

Abstract: 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.

Abstract: (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.