Patent GB-800713-A (GB)
Title: Sulphur-containing benzoxazole derivatives and compositions containing them
Inventor: STEVENSON HERBERT AUBREY
IPC: C07D263/56
Filed: 1955-04-27
Abstract: The invention comprises compounds having the general formula <FORM:0800713/IV (b)/1> in which m and n have the values 0 or 1 such that m has the value 0 when n has the value 1 and the benzene nucleus X is substituted by one or more radicals selected from chlorine, bromine, fluorine and iodine atoms and nitro groups, and m has the value 1 when n has the value 0 and the benzene nucleus X is unsubstituted or substituted by one or more radicals as hereinbefore specified. The compounds of the class where m is 0 and n is 1 may be prepared by heating benzoxazole-2-thiol with a benzyl halide, wherein the benzene nucleus is substituted as described above, in the presence of an alkaline condensing agent.  The compounds of the class where m is 1 and n is 0 may be prepared by ring closure of an o-(phenylthioacetylamino)-phenol of the formula HO.C6H5.NH.CO.CH2S.X, where the benzene nucleus X is unsubstituted or substituted, as described above, by known methods, for example, by heating with phosphorus pentoxide in an inert solvent.  The novel compounds are useful as active ingredients in acaricidal compositions ((see Group VI).  In examples: (1) 2 - (41 - bromobenzylthio)-benzoxazole is obtained by refluxing for 2 hours a mixture of p-bromobenzyl bromide, benzoxazole-2-thiol and anhydrous potassium carbonate in acetone; in a similar manner, 2-(41-chlorobenzylthio) - benzoxazole, 2 - (41 - nitrobenzylthio)-benzoxazole and 2-(41-fluorobenzylthio)-benzoxazole are obtained; (2) 2-(phenylthiomethyl) - benzoxazole is obtained by refluxing for 4 hours a mixture of o-(phenylthioacetylamino)-phenol and phosphorus pentoxide in dry benzene; (3) 2-(p-chlorophenylthiomethyl)-benzoxazole is obtained by refluxing for 6 hours a mixture of o-(p-chlorophenylthioacetylamino)-phenol and phosphorus pentoxide in toluene.  o-(Phenylthioacetylamino)-phenol is obtained by adding aqueous methanolic sodium hydroxide to a boiling solution of o-(chloroacetylamino)-phenol and benzenethiol in methanol and refluxing the mixture for 20 minutes.  o - (p - Chlorophenylthioacetylamino)-phenol is prepared in a similar manner from o-(chloroacetylamino)-phenol and p-chlorobenzenethiol.  The Provisional Specification describes also the preparation of 2-benzylthiobenzoxazole by refluxing a mixture of benzyl chloride, benzoxazole-2-thiol and anhydrous potassium carbonate in dry acetone.ALSO:An acaricidal composition contains as its active ingredient a compound of the formula <FORM:0800713/VI/1> in which m is 0 when n is 1 and the benzene nucleus X is substituted by one or more radicals selected from chlorine, bromine, fluorine or iodine atoms and nitro groups, and m is 1 when n is 0 and the benzene nucleus X is unsubstituted or substituted as indicated above, together with a diluent or carrier.  For preparation of the active compounds (see Group IV (b)).  Dusts, dispersions, emulsions and aerosols containing the above compounds are valuable for the control of the eggs and active stages of the plant feeding Tetranychidae or Red Spider mites, e.g. Tetranychua telaurius L. and Metatetranychus ulmi Koch and the Tea Red Spider mite Metatetranydus bisculatus Wood-Mason.  The active ingredient may be admixed with a dispersing and/or suspending agent such that a dispersion is formed when the mixture is added to water.  Such a composition may also contain a water-miscible organic solvent such as acetone. Other suitable dispersions comprise the active compounds in admixture with a dispersing agent, an emulsifying agent, a non-volatile oil, such as liquid paraffin, and water.  Suitable emulsions may comprise the active compound together with an emulsifying agent and an organic solvent, e.g. xylene or an aromatic solvent boiling in the range 80-300 DEG C.  It may be advantageous to add a non-volatile vegetable oil or mineral oil such as liquid paraffin.  The emulsion may also contain a wetting agent.  The aqueous dispersions and emulsions may be diluted with water to a concentration of active ingredient in the range 0.001-10 per cent w./v.  The compositions may also comprise dispersions of up to 50 per cent active compound in a pulverulent solid diluent.  Compositions suitable for dispersion as aerosols may contain the active compound dissolved in a volatile solvent, e.g. acetone, or in a high-boiling aromatic solvent such as xylene or non-volatile oil such as a vegetable oil together with cyclohexanone or acetone.  Such compositions are readily dispersed as aerosols by mechanical means or by incorporating a volatile propellant such as a mixture of chlorofluoro derivatives of methane and ethane.  Other compounds which are active against the adult stages of mites may be incorporated into the compositions, e.g. Parathion and "Malathion" (Registered Trade Mark).  In examples: (4) a dispersible powder is prepared by mixing 2-(41-bromobenzylthio)-benzoxazole with a condensate of formaldehyde and an alkyl aryl sulphonate, and kaolin; this composition may be added to water; (5) 2-(41-bromo - benzylthio) - benzoxazole is dissolved in a mixture of Insem 108 (an oleic acid ester of a glycol) and benzene to give a solution containing 5 per cent w./v. of active compound, the composition being suitable for dilution with water to obtain a stable emulsion; (6) a solution readily dispersed as an aerosol is obtained by dissolving 2-(41-bromobenzylthio)-benzoxazole in acetone to a concentration of 5 per cent w./v.; (7) an acaricidal dust comprises 5 parts by weight of 2-(41-bromobenzylthio) benzoxazole and 95 parts of kaolin.  Similar compositions may be obtained using 2-(41-chlorobenzylthio)-benzoxazole, 2 - (41 - nitrobenzylthio) - benzoxazole, 2-(41-fluorobenzylthio)-benzoxazole, 2-(phenylthiomethyl) - benzoxazole, and 2 - (p - chlorophenylthiomethyl) - benzoxazole.  The Provisional Specification describes also a dispersible powder comprising 2-benzylthiobenzoxazole, a condensate of formaldehyde and an alkyl aryl sulphonate, and kaolin which may be added to water to form a dispersion suitable for horticultural use.