Patent GB-694754-A (GB)
Title: Manufacture of methines of the styryl type and of photographic emulsions containing the same
IPC: C07D231/06
Filed: 1951-03-27
Abstract: 1 : 2 : 5 - Trimethylpyrazolium iodide is prepared by heating together 5-methylpyrazole and methyl iodide in a sealed tube. 1-Phenyl-2 : 5 - dimethylpyrazolium iodide, 1 : 2 - di - n-propyl - 3 - phenyl - 5 - methylpyrazolium iodide, and 1 - phenyl - 2 - ethyl - 3 : 5 - dimethylpyrazolium iodide are similarly prepared.  1 - Phenyl - 2 : 3 : 5 - trimethylpyrazolium iodide is prepared by heating together acetylacetone with excess phenylhydrazine, acidifying with sulphuric acid, steam distilling, and refluxing the oil obtained with excess methyl iodide, decolorizing with SO2, treating with dilute aqueous NaOH, and extracting with chloroform.ALSO:Methine dyes are prepared by condensing a pyrazolium salt, which is substituted in at least one of the positions 3 and 5 of the pyrazole nucleus by a methyl group, with a suitable intermediate, e.g. an aromatic aldehyde, preferably in the presence of an alkali metal alcoholate with heating.  The pyrazolium salt may be 1 : 2 : 5-trimethylpyrazolium iodide, 1-phenyl-2 : 5 - dimethylpyrazolium iodide, 1 - phenyl - 2 : 3 : 5 - trimethylpyrazolium iodide, 1 : 2 : 3 : 5-tetramethylpyrazolium iodide, 1 - phenyl - 2 - ethyl - 3 : 5 - dimethylpyrazolium iodide, or 1 : 2 - di - n - propyl - 3 - phenyl - 5 - methylpyrazolium iodide, and the aldehyde may be benzaldehyde, anisaldehyde, p-dimethylaminobenzaldehyde, cinnanaldehyde, p-dimethylaminocinnamaldehyde, or pyrene - 3 - aldehyde.  Where the pyrazolium salt contains two methyl groups, two molecular proportions of the same aldehyde may be used, or one molecular proportion of each of two different aldehydes may be used simultaneously or successively to effect reaction with both methyl groups.  5 - Styryl - 1 : 2 - dimethylpyrazolium iodide is prepared by refluxing together 1 : 2 : 5-trimethylpyrazolium iodide, benzaldehyde, sodium methoxide, and methanol.  5 - p - Dimethylaminostyryl - 1 : 2 - dimethylpyrazolium iodide, 5 - p - dimethylaminophenylbutadienyl 1 : 2 - dimethylpyrazolium iodide, 5 - styryl - 1-phenyl - 2 - methylpyrazolium iodide, 5 - p - methoxystyryl - 1 - phenyl - 2 - methylpyrazolium iodide, 5 - p - dimethylaminophenylbutadienyl - 1 - phenyl - 2 - methylpyrazolium iodide, 3 : 5 - bis - styryl - 1 - phenyl - 2 - methyl - pyrazolium iodide, 3 : 5 - bis - p - methoxystyryl - 1 - phenyl - 2 - methylpyrazolium iodide, 3 : 5 - bis - p - dimethylaminostyryl - 1 - phenyl - 2 - methylpyrazolium iodide (from which may be derived the perchlorate), 3 : 5-bis-p-dimethylaminophenylbutadienyl - 1 - phenyl - 2 - methyl - pyrazolium iodide, 3 : 5 - bis - p - dimethyl - aminostyryl - 1 : 2 - dimethylpyrazolium iodide, 3 : 5 - bis - p - dimethylaminophenylbutadienyl - 1 : 2 - dimethylpyrazolium iodide, 3 - p - dimethylaminophenylbutadienyl - 5 - p - dimethylaminostyryl - 1 : 2 - dimethylpyrazolium iodide, 3 - pyrene - (3) - vinyl - 5 - p - dimethylaminostyryl - 1 : 2 - dimethylpyrazolium iodide, 5 - p - dimethylaminostyryl - 1 : 2 - di - n - propyl - 3 - phenylpyrazolium iodide, 5 - p - dimethylaminophenylbutadienyl - 1 : 2 - di - n - propyl - 3 - phenylpyrazolium iodide, 3 : 5 - bis - p - dimethylaminostyryl - 1 - phenyl - 2 - methylpyrazolium iodide, and 3 : 5 - bis - p - dimethylaminophenylbutadienyl - 1 - phenyl - 2 - ethylpyrazolium iodide, are similarly prepared.