Patent GB-670998-A (GB)
Title: Improvements in or relating to substituted methine dyestuffs and to photographic silver halide emulsions containing the same
Inventor: KENDALL JOHN DAVID
IPC: C09B23/01
Filed: 1949-09-15
Abstract: Dyes of the general formula <FORM:0670998/IV (c)/1> wherein R1 is alkyl, R2 and R3 are alkyl o aralkyl, D is the residue of a 5- or 6-membered heterocyclic nucleus, and n is 0 or 1 are prepared by condensing a compound of the general formula <FORM:0670998/IV (c)/2> with an alkyl or aralkyl quaternary salt of a 5- or 6-membered heterocyclic nitrogen compound having a thioether group in a  or g -position to the quaternary nitrogen atom.  The condensation may be effected in the presence of a basic condensing agent.  The quaternary salt may be formed in situ and the dye prepared by fusing together the compound of the second general formula, the heterocyclic nitrogen base containing a thioether group in a - or g -position to the heterocyclic nitrogen atom, and an alkyl or aralkyl ester.  Ethyl 4 - (3 - methyl - 2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - methoxy - 2 - cyano - 2-butenoate is prepared by fusing together ethyl 2 - cyano - 3 - methoxy - 2 - butenoate, methyl p - toluenesulphonate, and 2 - methylthiobenzthiazole, adding ethyl alcohol and triethylamine, and refluxing.  Ethyl 4-(3-methyl-2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - ethoxy-2 - cyano - 2 - butenoate, methyl 4 - (3 - methyl-2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - methoxy-2 - cyano - 2 - butenoate, methyl 4 - (3 - methyl-2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - ethoxy-2 - cyano - 2 - butenoate, ethyl - 4 - (3 - ethyl-2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - ethoxy-2 - cyano - 2 - butenoate, methyl 4 - (3 - ethyl-2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - methoxy-2 - cyano - 2 - butenoate, ethyl 4 - (1 - methyl-1 : 2 - dihydroquinolylidene - 2) - 3 - ethoxy - 2-cyano - 2 - butenoate, ethyl 4 - (1 - methyl - 1 : 2-dihydroquinolylidene - 2) - 3 - methoxy - 2 - cyano-2 - butenoate, methyl 4 - (1 - methyl - 1 : 2-dihydroquinolylidene - 2) - 3 - methoxy - 2 - cyano-2 - butenoate, methyl 4 - (1 - methyl - 1 : 2-dihydroquinolylidene - 2) - 3 - ethoxy - 2 - cyano-2 - butenoate, ethyl 4 - (3 - methyl - 2 : 3 - dihydro-4 : 5 - benzbenzthiaolylidene - 2) - 3 - ethoxy - 2-cyano - 3 - butenoate, ethyl 4 - (3 - methyl - 2 : 3-dihydro - 6 : 7 - benzbenzthiazolylidene - 2) - 3-ethoxy - 2 - cyano - 2 - butenoate, methyl - 4-(3 - methyl - 2 : 3 - dihydro - 6 : 7 - benzbenzthiazolylidene - 2) - 3 - methoxy - 2 - cyano - 2-butenoate, methyl 4 - (3 - methyl - 2 : 3 - dihydro-4 : 5 - benzbenzthiazolylidene - 2) - 3 - methoxy-2 - cyano - 2 - butenoate, ethyl 4 - (3 - methyl-5 : 6 - dimethoxy - 2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - ethoxy - 2 - cyano - 2 - butenoate, methyl 4 - (3 - methyl - 5 : 6 - dimethoxy - 2 : 3-dihydrobenzthiazolylidene - 2) - 3 - methoxy - 2-cyano - 2 - butenoate, ethyl 4 - (3 : 6 - dimethyl-2 : 3 - dihydrobenzoxazolylidene - 2) - 3 - ethoxy-2 - cyano - 2 - butenoate, methyl 4 - (3 : 6 - dimethyl - 2 : 3 - dihydrobenzoxazolylidene - 2)- 3-methoxy - 2 - cyano - 2 - butenoate, ethyl 4-(3 : 5 : 6 - trimethyl - 2 : 3 - dihydrobenzoxazolylidene - 2) - 3 - ethoxy - 2 - cyano - 2 - butenoate, and methyl 4 - (3 : 5 : 6 - trimethyl - 2 : 3-dihydrobenzoxazolylidene - 2) - 3 - methoxy - 2-cyano-2-butenoate are similarly prepared.  According to the Provisional Specification, the methyl group of the intermediate may be replaced by a higher alkyl group, and in this case the first methine group of the resulting dyes carries an alkyl substituent.