GB785628A - Improvements in or relating to the production of skeletal muscle relaxant comprising5-chlorobenzoxazoles - Google Patents

Abstract

The invention comprises 5-chlorobenzoxazoles of the general formula <FORM:0785628/IV (a)/1> where R is an amino or a hydroxy group or a salt thereof. One method of preparing 2-amino-5 - chloro - benzoxazole comprises heating 2 - hydroxy-5-chlorophenylthiourea which removes hydrogen sulphide with subsequent ring-closure. Preferably the heating is effected in a liquid medium, the removal of hydrogen sulphide being facilitated by rendering the medium alkaline or by including in the reaction medium a metal compound forming an insoluble sulphide, e.g. a chloride, acetate or sulphate of lead, copper, iron, nickel, cobalt, silver, mercury, uranium, tin or gold suitably in the presence of a base. Another method comprises subjecting a 5-chlorobenzoxazole having at the carbon atom in the 2-position an atom or group replaceable by an amino group, to the action of an aminating agent. The replaceable group may be halogen or -SO3H, in which case the aminating agent may be ammonia or an amine such as benzylamine or hydrazine, reduction of the product being necessary in the case of the two latter compounds. Where the replaceable atom is hydrogen, amination of the benzoxazole derivative may be effected by heating with hydroxylamine, suitably by boiling in neutral or alkaline medium. 2 - Hydroxy - 5 - chlorobenzoxazole can be prepared by hydrolysing 2-amino-5-chloro-benzoxazole or by heating 2-hydroxy-5-chlorophenyl-urea or 2-hydroxy-5-chlorophenyl-thiourea in acid solution. In examples A to E, 2-amino-5-chlorobenzoxazole is prepared by heating 2-hydroxy-5-chlorophenylthiourea (A) in hot water, (B) in aqueous sodium hydroxide, (C) in the presence of methanol and yellow lead oxide, (D) in the presence of methanol and cupric chloride, (E) in the presence of methanol and ferric chloride. In further examples 2-amino-5-chlorobenzoxazole is prepared by (F) heating 5-chlorobenzoxazole with hydroxylamine, (G) shaking 2,5-dichlorobenzoxazole with aqueous ammonia. 2-Hydroxy-5-chlorobenzoxazole is prepared by (H) refluxing 2-amino-5-chlorobenzoxazole with normal hydrochloric acid, (I) refluxing N-(5-chloro-2-hydroxyphenyl) urea in dilute hydrochloric acid. 2-Amino-5-chlorobenzoxazole forms salts with acids such as hydrochloric, hydrobromic, hydroiodic, nitric, sulphuric, phosphoric, acetic, propionic, caproic, stearic, crotonic, fumaric, oleic, citric, tartaric, lactic, benzoic, naphthoic, salicylic, methane sulphonic and camphor sulphonic acids. The 2-hydroxy-5-chlorobenzoxazole forms salts with bases, such as alkali metal, alkaline earth metal, ammonium or substituted ammonium, e.g. ethanolamine and ethylene diamine salts. Starting materials. 5 - Chloro - 2 - hydroxy-phenyl-thiourea may be prepared by reacting 2-amino-4-chlorophenol with a thiocyanate, such as ammonium thiocyanate, in aqueous acidic medium.ALSO:A preparation for the relief of spasticity comprises a 5-chlorobenzoxazole having the general formula <FORM:0785628/VI/1> where R is an amino or a hydroxy group, or a salt thereof, together with a pharmaceutical carrier. 2-Amino-5-chlorobenzoxazole salts referred to are those with hydrochloric, hydrobromic, hydroiodic, nitric, sulphuric, phosphoric, acetic, propionic, caproic, stearic, crotonic, fumaric, oleic, citric, tartaric, lactic, benzoic, naphthoic, salicylic, methane sulphonic and camphor sulphonic acids. 2-Hydroxy-5-chlorobenzoxazole salts mentioned are alkali metal, alkaline earth metal, ammonium and substituted ammonium, e.g. ethanolamine and ethylenediamine salts. The compositions can be in the form of solutions, suspensions in liquid media, capsules, tablets and powders. The preparation is described of compositions containing as carrier (1 to 12) and (44 to 48) dilute aqueous hydrochloric acid; (13 to 43 and 50 and 51) polyethylene glycol, sodium carboxymethyl cellulose and water; (52 to 63) aqueous sodium hydroxide; (64) milk sugar, dibasic calcium phosphate, starch and calcium stearate. Alternative ingredients are sucrose, polyethylene glycol, mannitol, calcium carbonate, acacia solution, glucose, carboxymethyl-cellulose, shellac, magnesium stearate, stearic acid, kaolin or talc; (67) propylene glycol, sorbitol solution, alcohol, carboxymethylcellulose, sugar, p-hydroxy-benzoic acid methyl and propyl esters, polyoxyethylene sorbitan mono-oleate, flavouring, citric acid and water. Polyethylene glycol and/or glycerine are alternative ingredients.