Patent GB-751755-A (GB)
Title: Substituted methane-phosphonic acids and derivatives thereof
IPC: C07F9/38
Filed: 1953-12-08
Abstract: The invention comprises methane-phosphonic acids of general formula <FORM:0751755/IV(a)/1> wherein Ar is a substituted or unsubstituted aromatic radical and Y is an oxygen or sulphur atom; or a salt, ester, half-ester or salt of a half-ester thereof.  They may be prepared by reacting a salt or ester of a halogen-methanephosphonic acid and a phenol or thiophenol in the presence of an acid-binding agent.  When a salt of a halogen-methane-phosphonic acid is used, a salt of the corresponding aryl-oxy- or aryl-thio-methane-phosphonic acid is formed.  When an ester of a halogen-methane-phosphonic acid is reacted with one equivalent of a phenol or thiophenol, the reaction products are a salt of a half-ester of the halogen-methanephosphonic acid and an aryl ether or thioether. Reaction with a further equivalent of the phenol or thiophenol gives the salt of a half-ester of an aryl-oxy- or aryl-thio-methanephosphonic acid.  The two-stage process may be avoided by reacting the ester with two equivalents of a phenol or thiophenol.  The salts of half-esters thus obtained are converted to acids, salts, or esters by known methods.  Specified salts of halogen-methane-phosphonic acids are those of alkali or alkaline earth metals, ammonia and organic bases; specified esters are those of methanol, ethanol, isopropanol, phenol, cresol and 4-chlorophenol. Specified acid-binding agents are the hydroxides and carbonates of sodium, potassium, ammonium and the alkaline earth metals, and also organic bases.  Phenols and thiophenols specified are phenol, 1 : 2-, 1 : 3- or 1 : 4-cresol, 4-isobutyl or -isooctyl phenol, 2 : 4-xylenol, mesitol, 2- or 4-chlorophenol, 2 : 4-dichlorophenol, 4 - bromophenol, 4 - chloro - 2 - methylphenol, 2 : 4 : 5-trichlorophenol, pentachlorophenol, 4-phenylphenol, 4-nitrophenol, guaiacol, a - or b -naphthol, thiophenol, 4-methyl- or -chloro- or -bromo- or -iodo- or -nitro-thiophenol, 2 - nitrothiophenol, 4 - chloro - 2-methyl- or -nitro-thiophenol, 2 : 4-dichloro- or -dinitro - thiophenol, 2 : 4 : 5 - trichlorothiophenol, 1- or 2-thionaphthol and 4-chloro-1-thionapthol.  The reaction is preferably carried out in a solvent such as a lower aliphatic alcohol, at temperatures above 50 DEG  C. and in a pressure vessel.  In examples:  (1) the dimethyl ester of chloromethane-phosphonic acid was heated under pressure in methanol solution with 2 : 4-dichlorophenol and sodium methylate, the 2 : 4-dichloranisole was removed and 2 : 4-dichlorophenoxymethane-phosphonic acid monomethyl ester obtained on acidification and converted into the corresponding acid and dimethyl ester; (2) p-cresol or p-nitrophenol was reacted with the dimethyl ester of chloromethane-phosphonic acid and sodium methylate to give the sodium salt of the methyl monoester of chloromethane phosphonic acid and p-methyl- or -nitro-anisole, the sodium salt of the mono-ester being subsequently reacted with the sodium salt of 2 : 4-dichlorophenol to give 2 : 4-dichlorophenoxymethane-phosphonic acid-monomethyl ester; (3) as in (1) using p-cresol, the monomethyl ester of p-methyl-phenoxymethane-phosphonic acid, and the free acid were obtained; (4) as in (1) using b -naphthol to give the methyl mono-ester of b -napthoxy - methane - phosphonic acid, the free acid being obtained by hydrolysis with potassium hydroxide solution followed by acidification; (5) as in (1) using thiophenol; phenylmercapto - methane - phosphonic acid monomethyl ester was obtained; (6) the sodium salt of chloromethane phosphonic acid was reacted with the sodium salt of 2 : 4-dichlorophenol in methanol solution to give the sodium salt of 2 : 4-dichlorophenoxymethane-phosphonic acid, the acid being obtained by acidification with dilute sulphuric acid.