Patent GB-674169-A (GB)
Title: Improvements in or relating to pyridinium salts and the preparation thereof
Filed: 1949-03-01
Abstract: A process for preparing quaternary pyridinium salts having the formula <FORM:0674169/IV (b)/1> in which R1 and R11 denote alkyl, aralkyl, aryl or hydroaryl radicals which may be alike or different or together denote a polymethylene ring containing not more than 5 carbon atoms, R111 denotes hydrogen, halogen or an aliphatic or araliphatic radical containing not more than 10 carbon atoms and RIV denotes an aralkyl radical and X a quaternizing anion comprises first reacting a 3-pyridol having the formula <FORM:0674169/IV (b)/2> with a carbamyl halide <FORM:0674169/IV (b)/3> and reacting the resulting reaction product with a compound of the formula RIVX.  The 3-pyridol may contain radicals R111, selected from e.g. methyl, benzyl or styryl radicals or iodine or chlorine atoms.  The carbamyl halide may be a dimethyl-, methyl-p-chlorphenyl, diphenyl, methyl benzyl-, methyl cyclohexyl-, methyl cyclohexenyl-, or tetramethylene carbonyl chloride or the corresponding bromide or iodide.  Compounds RIVX may be e.g. benzyl, phenylethyl or naphthylmethyl chlorides or bromides or their methoxy, ethoxy, halo or nitro derivatives.  The 3-pyridol and carbamyl halide may be reacted in a solvent, e.g. benzene with an acid binding agent, e.g. triethyl amine.  In an example (1), dimethylcarbamyl chloride and 3-pyridol are reacted to give the dimethyl carbamyl ester and the product is quaternated by reaction with benzyl bromide.  Similarly prepared are (2) 1 - benzyl - 3 - (dimethylcarbamyloxy)-pyridinium chloride; (3) 1-benzyl-3-(N-tetramethylenecarbamyloxy) - pyridinium bromide; (4) 1 - benzyl - 3 - (N - benzyl - N - methylcarbamyloxy)-pyridinium bromide; (5) 1-benzyl - 3 - (dibenzylcarbamyloxy) - pyridinium bromide; (6) 1-(2-naphthylmethyl)-3-(dimethylcarbamyloxy) - pyridinium chloride; (7) 1-benzyl - 3 - (dimethylcarbamyloxy) - 6 - methyl pyridinium bromide; (8) 1-(p-methoxybenzyl)-3 - (dimethylcarbamyloxy) - pyridinium bromide.  1 - Benzyl - 3 - (dimethylcarbamyloxy)-pyridinium dihydrogen phosphate (3) and (4) the corresponding pyridinium picrate, are prepared by reacting the product of (1) with (3) silver phosphate and (4) picric acid.  As open to inspection under Sect. 91, the Specification comprises the production of compounds of the first general formula above in which RIV additionally represents a "quaternizing radical," e.g. suitable quaternizing compounds may be alkyl, alkylene or hydroxyalkyl halides, e.g. methyl chloride or bromide, n-propyl chloride, allyl or methallyl bromide or b -hydroxyethyl chloride or a thienylmethyl halide.  Also included is the production of bis-compounds, e.g. methylene-bis-(1-(3-dimethylcarbamyloxy) - pyridinium chloride or 1,2-ethylene - bis - (1 - (31 - dimethylcarbamyloxy)-pyridinium bromide by reaction of a methylene-or 1,2-ethylene-halide with a compound of the general formula  <FORM:0674169/IV (b)/4> Examples describe the preparation by a method similar to (1) above of (5) 3-(dimethylcarbamyloxy)-1-methyl pyridinium bromide; (6) the corresponding methiodide which is then converted to the picrate; (8) 1-(2-thienyl methyl) - 3 - (dimethylcarbamyloxy) - pyridinium chloride; (14) 1,2,6-trimethyl-3-(dimethylcarbamyloxy)-pyridinium bromide; (15) 1-methyl - 2 - iodo - 3 - (dimethylcarbamyloxy)-pyridinium iodide. Other such compounds contain 1 - (b  - hydroxyethyl) - and 1 - n - butyl radicals.  1 - Benzyl - 3 - (dimethylcarbamyloxy)-pyridinium dihydrogen phosphate and the corresponding pyridinium picrate are prepared by reacting the product of example (1) with silver phosphate and picric acid respectively. This subject-matter does not appear in the Specification as accepted.