Abstract: The present invention relates to a process for preparing a compound of formula (I) ##STR1## wherein R is an heterocyclic group which contains at least one nitrogen atom with or without oxygen or sulphur and R.sup.1 and R.sup.2 are both hydrogen atoms or one of them is an hydrogen atom and the other is an acyl group; the process comprising reacting a compound of formula (II) ##STR2## wherein R.sup.1 and R.sup.2 are each as defined above, and wherein, if necessary, any reactive group is protected by a suitable protective group, or a salt thereof, with a compound of formula (III)R--SH (III)wherein R is as defined above, or a salt thereof, in the presence of an acid and of a compound of formula (IV) ##STR3## wherein each of R.sup.3 and R.sup.4 is a C.sub.1 -C.sub.4 alkyl group or R.sup.3 and R.sup.4 taken together are a C.sub.2 or C.sub.3 alkylene chain and, if necessary, removing the protective groups possibly present.

Abstract: A process for the preparation of a pyrazine derivative of the formula ##STR1## wherein R.sub.1 represents hydroxy, C.sub.1 -C.sub.6 alkoxy, or a group of the formula NR.sub.2 R.sub.3 in which R.sub.2 and R.sub.3 are independently a hydrogen atom or C.sub.1 -C.sub.6 alkyl or, together with the nitrogen atom to which they are linked, form a saturated ring having five or six atoms which may contain one or more additional heteroatoms; which process comprises reacting a compound of the formula: ##STR2## wherein R represents a hydrogen atom, C.sub.1 -C.sub.6 alkyl, or C.sub.1 -C.sub.6 alkoxy, Y represents a hydrogen atom or a sodium, lithium, or potassium ion, and A is a nitrile group or a substituent of the formula COR.sub.1 where R.sub.1 is as defined above either with pyruvic aldehyde oxime of the formula: ##STR3## or with a pyruvic aldehyde oxime acetal derivative of the formula: ##STR4## wherein R.sub.4 and R.sub.5 are independently a hydrogen atom or C.sub.1 -C.sub.

Abstract: The present invention relates to a new class of compounds belonging to the anthraquinone series, having the general formula: ##STR1## wherein R, R', R", R'", R' are indifferently H or Chlorine, ##STR2## Such compounds exhibit a color varying from yellow to violet depending on the nature and position of substituents R, R', R", R'", R'.sup.v and, in virtue of their excellent stability characteristics, they are particularly useful as pigments and vat dyes.This invention relates furthermore to the preparation of compounds having general formula (I) and to the utilization thereof, particularly in the following applications:Pigmentation of plastic materials, such as polyvinyl chloride, polystyrene, polyolefins, polymethylmethacrylate, polycarbonates and ABS copolymers (acrylonitrile-butadiene-styrene);Pigmentation of varnishes, stoving enamels, inks and pastes for the printing of textiles;Vat dyeing of cellulose fibres such as cotton, flax, rayon.

Abstract: Process for the preparation of the monopotassium salt of 1,2,5-thiadiazol-3,4-dicarboxylic acid (I). Involves double-stage saponification of 3,4-dicyano-1,2,5-thiadiazole (II), 3-cyano-4-carbamoyl-1,2,5-thiadiazole (III) is obtained from an aqueous suspension of 3,4-dicyano-1,2,5-thiadiazole (II) by catalytic hydration through the addition of aqueous KOH, desirably at a temperature of from 20.degree. to 50.degree. C. and with a molar ratio of 3,4-dicyano-1,25-thiadiazole (II) to KOH of from 1:0.01 to 1:0.8. This is followed by hydrolysis, by the further addition of aqueous KOH, desirably at a temperature of from 85.degree. to 100.degree. C., until attaining an overall molar ratio of 3,4-dicyano-1,2,5-thiadiazole (II) to KOH of from about 1:2.0 to 1:2.35, a molar ratio of 3,4-dicyano-1,2,5-thiadiazole (II) to H.sub.2 O of from about 1:20 to 1:23.

Abstract: 3,4-DICYANO-1,2,5-THIADIAZOLE IS PREPARED BY REACTING DIAMINOMALEONITRILE (DAMN) with thionyl chloride (SOCl.sub.2) at a temperature of 40.degree. C. up to the boiling point of thionyl chloride wherein the molar ratio of SOCl.sub.2 /DAMN is between 2:1 and 10:1.

Abstract: New compounds are disclosed having the general formula: ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 may be the same or different and are selected from the class consisting of H, Cl and OCH.sub.3. They are useful as pigments. They are prepared by reacting a substituted or unsubstituted 1-aza-2-hydroxybenzanthrone with 2,3-dichloro-1,4-naphthoquinone, in the presence of pyridine, at a temperature between 80.degree. and about 120.degree. C.

Abstract: A process is disclosed for the preparation of 2-hydroxybenzanthrone and substituted derivatives thereof having the general formula: ##STR1## wherein: R.sub.1 = H, OHR.sub.2, r.sub.3 = h, cl, --OH, --OCH.sub.3, ##STR2## characterized in that an anthraquinone-1-diazonium salt is reacted with an olefinic compound of the formula: ##STR3## wherein X = CN or OCOCH.sub.3, in an alcoholic medium of a lower monovalent alcohol and in the presence of a catalytic quantity of cuprous chloride, at a temperature between 20.degree. and 100.degree. C, and that the reaction intermediate thus obtained is reacted successively with alkali in alcoholic solution.

Abstract: 1-AZA-2-HYDROXYBENZANTHRONE, USEFUL AS AN INTERMEDIATE FOR SYNTHESIZING DYES IS OBTAINED BY THE DIRECT REACTION OF ALKYL ESTERS OF ANTHRAQUINONE-1-ACETIC ACID WITH AMMONIA IN HYDROXYLATED SOLVENTS AND IN THE PRESENCE OF STRONG BASES AND/OR REDUCING SUBSTANCES.

Abstract: A new process for preparing 3,3 - thio - bis[2-Methoxy-1-azabenzanthrone], a useful intermediate in the synthesis of dyestuffs, is disclosed. The process involves reacting 2-methoxy-1-azabenzanthrone with sulfur chlorides in suspension or solution in an inert solvent under heating, and recovering the reaction product from the reaction mass, e.g., by filtering.