Patent GB-360958-A (GB)
Title: Process for the manufacture of esters of the leuco compounds of vat dyestuffs
IPC: C09B9/00
Filed: 1930-08-12
Abstract: Leuco compounds of vat dyes, esters of.--Acid sulphuric esters of leuco compounds of indigoid vat dyes containing nitro groups are obtained, without reduction of the nitro groups, (a) by the processes of Specification 360,907, involving reduction of the vat dye with hydrogen sulphide in the presence of a tertiary base, followed by esterification of the leuco compound with sulphur trioxide or an agent yielding the same, (b) by treating the vat dye with sulphur trioxide or an agent yielding the same in the presence of a metal powder and a tertiary base (compare Specifications 247,787, 251,491, 278,399 and 304,436, [all in Class 2 (iii), Dyes &c.]), or (c) by reducing the vat dye with a mixture of sulphur dioxide and formic acid in the presence of a tertiary base (compare Specification 299,899, [Class 2 (iii), Dyes &c.]), and treating the product with sulphur trioxide or an agent yielding the same.  In examples (1) the dye obtained from 5-nitroisatin chloride and 2 : 1-naphthoxythiophene is reduced with hydrogen sulphide in dry pyridine, and the solution obtained is esterified by means of pyridine and chlorsulphonic acid, (2) 7 : 7<1>-dinitrothioindigo is similarly treated (3) the dye obtained by condensing a reactive a  - derivative of 5-nitro-6 : 7-benzo-(Bz-1 : 4-dichloro)-isatin, obtained by treating 6 : 7-benzo-(Bz 1 : 4-dichlor)-isatin (Specification 286,358, [Class 2 (iii), Dyes &c.]), with nitric acid, with 4 : 5-benzo-oxythionaphthene, is introduced into an esterification mixture comprising chlorsulphonic acid and pyridine, and treated with hydrogen sulphide, (4) the dye obtained from a reactive a  - derivative of 5-nitroisatin and 1 : 2-naphthoxythiophene is treated with pyridine, chlorsulphonic methylester and copper powder; the product when dyed on wool or printed on cotton and developed with oxidizing agents gives corinth shades, (5) 7 : 7<1>-dinitrothioindigo is treated with chlorsulphonic methylester and pyridine in chlorbenzene with addition of copper powder, (6) the same dye as that used in example 3 is esterified by treatment with pyridine, sulphur trioxide and copper powder; other dyes which may be similarly treated are the products from 5-brom-7-nitroisatin chloride (obtained by nitrating 5-bromisatin in sulphuric acid) and 2 : 1-naphthoxythiophene, a  - anthrol, 1-chlor-2 : 3-naphthoxythiophene, or 4 : 7-dimethyl-5-chlor-oxythionaphthene (made by converting 2 : 5-dimethyl-4-chlorphenylthioglycollic acid into the acid chloride and ring-closing with aluminium chloride), or from 5-nitro-9-chlor-1 : 2-naphthisatin chloride and 2 : 1-naphthoxythiophene, (7) the dye from a 5-nitroisatin a  - derivative and 4-chlor-1- naphthol is treated with pyridine, chlorsulphonic methylester and zinc powder, (8) the dye from 5-nitroisatin chloride and 6 : 7-benzo- (Bz-4-chlor)-oxythionaphthene is reduced with sulphur dioxide and formic acid in pyridine and the solution thus obtained esterified with chlorsulphonic acid or its methylester and pyridine, and (9) the dyes from 5-nitro-6 : 7-benzo-(Bz-4-chlor)-isatin chloride and 4 : 5-benzo-oxythionaphthene, 5-nitroisatin chloride and 4-chlor-1-naphthol, and 7 : 7<1>-dinitrothioindigo are similarly treated.  The nitro groups in the products can be reduced to amino groups by treatment with alkaline reducing agents.  Specifications 3135/06, [Class 2, Acids and salts, Organic &c.], and 233,831, [Class 2 (iii), Dyes &c.], are also referred to.