GB1324904A - Dibenzothiophene dioxide derivatives - Google Patents

Abstract

1324904 Bis-benzoxazolyl-dibenzothiophene dioxides SANDOZ Ltd 19 April 1971 [20 Feb 1970 23 Dec 1970] 22151/71 Heading C2C [Also in Divisions C3 and D1] The invention comprises compounds of the formula in which each R 1 and R 2 is hydrogen, halogen, carboxy, carbalkoxy, or alkyl, alkenyl or aryl which may be substituted, e.g. by halogen, alkoxy, alkoxyalkoxy, cyano, phenyl, methylphenyl, phenoxy or methylphenoxy; m and n are 1-3; and the rings A 1 and A 2 may carry non-water-solubilizing substituents, such as halogen, or C 1-6 alkyl or alkoxy; and their production by reacting one mole of a compound in which X is CN, COOH, CO halogen, optionally substituted CONH 2 , or COOR 3 where R 3 is alkyl, aryl of the benzene series or benzyl, with one mole of a compound or a salt thereof and with one mole of a compound or a salt thereof, and carrying out ring closure at an elevated temperature, e.g. in an organic solvent of b.p. above 150‹ C. in the presence of a cyclization catalyst such as boric acid, anhydride, trifluoride, or trifluoride etherate, zinc chloride, polyphosphoric acid, pyrophosphoric acid, phosphorus trichloride or oxychloride, and aromatic and aliphatic sulphonic acids. The compounds of the invention are optical brightening agents. The reaction of dibenzothiophene-5,5-dioxide- 3,7-dicarboxylic acid with SOCl 2 gives the acid chloride, which with methanol gives the dimethyl ester.