Patent GB-499836-A (GB)
Title: Manufacture of n:n-dialkyl-dipyrazol-anthronyls
IPC: C09B5/08
Filed: 1937-07-30
Abstract: N : N1-Dialkyl-2 : 21-dipyrazolanthronyls are manufactured by treating a 2 : 21-dipyrazolanthronyl with an alkylating agent of which the alkyl residue is branched and contains no alkoxy group, or by treating a pyrazolanthrone, which may be substituted in the 2-position by halogen or a mercapto or sulphonic acid group, with an alkylating agent of the said kind and treating the product with a condensing agent, e.g. caustic alkali or copper, or with a reducing agent followed by oxidation of the resulting leuco-compound.  2 : 21-Dipyrazolanthronyls containing two different N-alkyl residues, one of which may contain an aryl radicle as a substituent, are manufactured by treating a 2 : 21-dipyrazolanthronyl simultaneously or successively with two alkylating agents providing different alkyl residues free from alkoxy groups, at least one of which is a branched alkyl residue, or by treating an N-monoalkyl-2 : 21-dipyrazolanthronyl, containing no alkoxy group in the alkyl residue, with an alkylating agent providing a different alkyl residue containing no alkoxy group, at least one of the alkyl residues being branched.  The alkylation may be effected at high temperature, e.g. 120-200 DEG  C., in an open vessel or under pressure, and, if desired, in the presence of a solvent or diluent.  When the alkylating agent is an isoalcohol, which contains a free hydroxyl group, it is preferable to work in the presence of an acid, whilst when using an ester, which contains no free hydroxyl group, it is preferable to use an alkali metal salt of the pyrazolanthrone or 2 : 21-dipyrazolanthronyl.  The N : N1-dialkyl-2 : 21-dipyrazolanthronyls may be treated with halogenating agents.  The products are dyestuff intermediates, or dyestuffs which may be used, if desired in admixture with N : N1-dimethyl- or diethyl-2 : 21-dipyrazolanthronyl or with N : N1-dimethoxyethyl- or diethoxyethyl-2 : 21-dipyrazolanthronyl, for dyeing or printing vegetable fibres, e.g. cotton, for dyeing artificial silk, e.g. acetate artificial silk, or for colouring lacquers and plastic masses. They may be purified by crystallization, by conversion into their salts with strong acids or by treatment with oxidizing agents, e.g. alkaline hypochlorite solution, and may be converted into their leuco-derivatives e.g. leuco-sulphuric esters.  In examples: (1) the dipotassium salt of 2 : 21-dipyrazolanthronyl is heated with p-toluenesulphonic acid isopropyl or sec. butyl ester in nitrobenzene or o-dichlorobenzene or 1 : 2 : 4-trichlorobenzene, in the presence of anhydrous potassium carbonate; (2) the dipotassium salt of 2 : 21-dipyrazolanthronyl is heated in 1 : 2 : 4-trichlorobenzene in the presence of potassium carbonate with p-toluenesulphonic acid ethyl and isopropyl esters, successively in either order or simultaneously; the ethyl ester may be replaced by the methyl ester, and the isopropyl ester by the sec. butyl ester; (3) the dipotassium salt of 2 : 21-dipyrazolanthronyl is heated in 1 : 2 : 4-trichlorobenzene in the presence of potassium carbonate with p-toluenesulphonic acid isopropyl ester, and the resulting N-monoisopropyl derivative is isolated and converted into the potassium salt, which is heated with ethyl bromide in the presence of copper acetate; (4) N : N1-diisopropyl-2 : 21-dipyrazolanthronyl is dissolved in fuming sulphuric acid and treated with bromine in the presence of iodine; the same product is obtained by dibrominating 2 : 21-dipyrazolanthronyl and isopropylating the product; the diisopropyl derivative may be replaced by another diisoalkyl derivative; (5) potassium pyrazolanthrone is heated in 1 : 2 : 4-trichlorobenzene in the presence of potassium carbonate with p-toluenesulphonic acid isopropyl ester, and the resulting N-isopropylpyrazolanthrone is heated with alcoholic caustic potash and the product oxidized by the passage of air; (6) cotton is dyed red shades with N : N1-diisopropyl-2 : 21-dipyrazolanthronyl from an alkaline hydrosulphite vat; (7) cotton is similarly dyed with N-ethyl-N1-isopropyl-2:21-dipyrazolanthronyl.  Other starting materials, alkylating agents and diluents specified are: N-monoalkyl-(e.g. methyl or ethyl) and N-monoaralkyl-(e.g. benzyl) 2 : 21-dipyrazolanthronyls, and halogen derivatives of these compounds and of 2 : 21-dipyrazolanthronyl; isoalcohols, their halides and their sulphuric acid esters, e.g. isobutyl, isopropyl and isoamyl alcohols and halides, the p-toluenesulphonic esters of isobutyl and isoamyalcohols, and esters of isoalcohols containing halogen, e.g. the p-toluenesulphonic ester of a  : a 1-dichlorhydrin; chlorobenzene, amyl alcohol, naphthalene and anisole. Specifications 14103/15, 263,494, and 322,008, [all in Class 2 (iii)], are referred to.  The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 498,126.  This subject-matter does not appear in the Specification as accepted.