Patent GB-377994-A (GB)
Title: Manufacture of arsenic compounds
IPC: C07F9/80
Filed: 1931-04-02
Abstract: Arseno compounds are prepared by reducing, either alone or together with another arsenic compound of the benzene series, a benzoxazole or benzimidazole compound containing a mercapto group in the heterocyclic nucleus and an arsonic acid group with at least one other substituent in the benzene nucleus; or by condensing a corresponding trivalent arsenic compound with another such compound or with a trivalent arsenic compound of the benzene series.  The products possess therapeutic properties.  According to the examples, (1) 7-chloro-2-mercaptobenzoxazole-5-arsonic acid is reduced to the arseno compound with hydrosulphite; (2) 7-chloro-2-mercaptobenzimidazole-4-arsonic acid is reduced with hypophosphorous and hydriodic acids to the corresponding arseno compound; (3) 7 : 7<1>-diacetyl-amino-5 : 5<1>-arseno-2 : 2<1>-dimercaptobenzoxazole is prepared from the corresponding arsonic acid by reduction with hydrosulphite or stannous chloride; (4) arseno-(2-mercaptobenzoxazole-7-amino-5) -(3<1>-amino-4<1>-hydroxybenzene-1) is obtained by interaction of 7-amino-2-mercaptobenzoxazole-5-arsenoxide with 1-arsine-3-amino-4-hydroxybenzene; (5) 6-carboxyl-2-mercaptobenzoxazole-5-arsonic acid is reduced with hydrosulphite to the arseno compound; (6) 7 : 7<1>-dimethoxy-5 : 5<1>-arseno-2 : 2<1>-dimercaptobenzoxazole is prepared by the hydrosulphite reduction of the corresponding arsonic acid; (7) 2-mercaptobenzaxazole-5-sulphonic acid-7-arsonic acid is reduced to the arseno compound with hypophosphorous acid; (8) 7:7<1>-dicarboxyl-5 : 5<1> - arseno-2 : 2<1> - dimercaptobenzoxazole is prepared by the hydrosulphite reduction of the arsonic acid; (9) 7 : 7<1>-diiodo-5 : 5-arseno-2 : 2<1>-dimercaptobenzoxazole results from the interaction of 7-iodo-2-mercaptobenzoxazole-5-arsenoxide with the corresponding arsine; (10) 7-amino-2-mercaptobenzoxazole-5-arsonic acid and the corresponding arsenoxide are added with cooling to an alcoholic solution of stannous chloride, hydrochloric acid and hydriodic acid, when the arseno compound separates out.  Arsonic acids. 7-Chloro-2-mercaptobenzoxazole-5-arsonic acid is prepared by treating 3-chloro-4-hydroxy - 5 - aminobenzene-1-arsonic acid with potassium xanthogenate and eliminating sulphur from the arsenic residue of the resulting 7-chloro - 2 - mercaptobenzoxazole-5-sulpharsonic acid by means of lead carbonate.  7-Chloro - 2 - mercaptobenzimidazole - 4 - arsonic acid is obtained from 3-nitro-4-chlorobenzene-1-arsonic acid by reduction, acylation e.g. acetylation of the amino product, nitration to give the 2-nitro compound, splitting off the acyl residue, reducing the nitro group, treating the diamino acid with potassium xanthogenate and removing sulphur from the arsenic residue of the 7-chloro-2-mercaptobenzimidazole-4-sulpharsonic acid formed. 7-Acetylamino-2-mercaptobenzoxazole-5-arsonic acid results from the nitration of 3-acetylamino-4-hydroxybenzene-1-arsonic acid, followed by reduction of the 5-nitro product, reaction of the amino acid with potassium xanthogenate and elimination of sulphur from the resulting sulpharsonic acid. 7-Amino-2-mercaptobenzoxazole-5-arsonic acid is obtained by saponification of the corresponding acetyl compound; it couples strongly with R-salt. 6-Carboxyl-2-mercaptobenzoxazole-5-arsonic acid is prepared by reducing 5-nitro-2-carboxyl - 4 - hydroxybenzene-1-arsonic acid, ring-closing the amino product with potassium xanthogenate and eliminating sulphur as before. 7-Methoxy-2-mercaptobenzoxazole-5-arsonic acid is formed when 3-methoxy-4-hydroxy-5-aminobenzene-1-arsonic acid, prepared by subjecting 1-amino-3-methoxy-4-hydroxybenzene to Bart's reaction p followed by nitration and reduction, is treated with potassium xanthogenate and the sulphur removed from the arsenic residue by means of lead carbonate.  2-Mercaptobenzoxazole-5-sulphonic acid-7-arsonic acid is prepared by converting 5-nitro-6-hydroxy-1-aminobenzene-3-sulphonic acid into the 1-arsonic acid by Bart's reaction, reducing to the 5-amino compound (which can couple with R-salt), and subjecting it to treatment with potassium xanthogenate and sulphur elimination as above.  7 - Carboxyl-2-mercaptobenzoxazole - 5 - arsonic acid is obtained from 1-amino-4-hydroxy-3-benzoic acid by subjecting it to Bart's reaction, nitrating and reducing, ring-closing the resulting 3-carboxyl-4-hydroxy - 5 - aminobenzene-1-arsonic acid with potassium xanthogenate and removing sulphur with lead carbonate.  Arsenoxides. 7 - Iodo - 2 - mercaptobenzoxazole-5-arsenoxide is prepared from 3-nitro-4-hydroxybenzene-1-arsonic acid by first treating it with iodine in the presence of mercury oxide, reducing the resulting 5-iodo compound, ring-closing the product with potassium xanthogenate, eliminating sulphur by means of lead carbonate from the arsenic residue of the 7-iodo-2 - mercaptobenzoxazole - 5 - sulpharsonic acid formed, and reducing the product with sulphurous and hydriodic acids. 7-Amino-2-mercaptobenzoxazole-5-arsenoxide is obtained by reduction with sulphurous acid of the corresponding arsonic acid.  Arsines.  7-Iodo - 2 - mercaptobenzoxazole-5-arsine is prepared by reduction of the corresponding arsonic acid by means of zinc dust and hydrochloric acid.