Patent GB-897095-A (GB)
Title: Process for the preparation of furan derivatives
IPC: G05F1/563
Filed: 1959-11-10
Abstract: Furan derivatives of formula <FORM:0897095/IV (b)/1> and their acid addition salts, in which A represents a benzene nucleus in which 2 adjacent carbon atoms are attached to 2 imidazole nitrogen atoms and R represents hydrogen, or an alkyl hydroxyalkyl or aralkyl radical are prepared by a method comprising reacting an o-diaminobenzene of the formula <FORM:0897095/IV (b)/2> with a dicarboxylic acid of formula <FORM:0897095/IV (b)/3> in a molar ratio of 2 : 1 at elevated temperature and in the presence of an oxygen-containing phosphoric acid as a dehydrating agent to split off at least 3 molecules of water if a tetrahydroxybutanedicarboxylic acid is used (the remainder of the 7 molecules of water to be split off being split off in known manner), or all 4 molecules if furan 2.5-dicarboxylic acid is used. In the case where a tetrahydroxy-butane carboxylic acid is used as starting material 4 molecules of water may be split off by known methods in the first stage to give an intermediate compound of formula <FORM:0897095/IV (b)/4> The o-diamino benzenes used as starting materials may contain nuclear substituents, such as chlorine or alkyl groups.  Suitable o-diamino benzenes are, for example, o-phenylene diamine, 1 - amino - 2 - methylamino benzene, 1,2 - diamino - 4 - methylbenzene, 1,2 - diamino - 4 - isopropylbenzene and 1, 2 - diamino - 4 - chlorobenzene.  Suitable tetrahydroxy dicarboxylic acids for use as starting materials are, for example, monosaccharic acid, idosaccharic acid and allomucic acid.  The splitting off of the molecules of water other than those split off by an oxygen-containing phosphoric acid may be carried out by heating in the presence of known dehydrating agents, e.g. hydrochloric or sulphuric acid.  The dehydration using the oxygen-containing phosphoric acid is preferably carried out at 150 DEG C.-220 DEG C. Suitable phosphoric acids are those of formula Hn+2PnO3n+1 in which n represents an integer.  The products may be alkylated, hydroxyalkylated or aralalkylated in known manner by treatment with alkyl halides, alkylene chlorhydrins or with aralkyl halides respectively. Dialkyl sulphates may also be used to effect alkylation.  The products may also be sulphonated by treatment with sulphuric acid monohydrate, chlorsulphonic acid or sulphuric acid containing sulphur trioxide.  The furan derivatives may also be converted to quaternary ammonium salts by reacting with, for example, alkylhalides, epichlor hydrin, dimethyl sulphate, benzyl chlorides which may be substituted in the nucleus by halogen, alkyl or alkoxy groups, toluene sulphponic acid esters, aryl sulphonic acid esters and halogen alkyl or aralkyl sulphonic acids. Specification 840,344 is referred to.ALSO:Furan derivatives of the formula <FORM:0897095/IV (c)/1> in which A is a benzene nucleus which may be substituted, for example, by chlorine or alkyl groups, and is attached by adjacent carbon atoms to the imidazole ring, and R is hydrogen or an alkyl, hydroxyalkyl or aralkyl radical, and their acid addition salts, may be used as optical brighteners for fibrous materials, e.g. protein, polyamide, polyacrylonitrile and acetylcellulose fibres, in neutral to weakly alkaline baths.