Patent GB-642517-A (GB)
Title: Improvements in or relating to polymethine dyestuffs
Inventor: EDWARDS HARRY DEREK
IPC: C09B23/01
Filed: 1948-10-02
Abstract: Methine dyes are prepared by reacting a compound of the general formula <FORM:0642517/IV (c)/1> or a stereoisomeric form thereof, wherein R1 is alkyl (including hexyl, octyl, and dodecyl), R3 is alkyl or aralkyl, and R4 is H or alkyl, with a compound of the general formula <FORM:0642517/IV (c)/2> wherein Q is a thioether group SR6 (R6 being alkyl) or a substituted or unsubstituted amino group, R5 is alkyl or aralkyl, X is an acid radical, n is 0 or 1, and D is the residue of a 5- or 6-membered heterocyclic nucleus, which may have substituted or unsubstituted carbocyclic rings fused thereto. Where Q is a thioether group, the heterocyclic thioether compound need not be isolated, and the quaternary salt of the heterocyclic compound containing a reactive methyl group in a - or g -position to the quaternary N atom may be reacted with a trialkyl trithio orthoformate in presence of acetic anhydride and the product reacted directly with the compound of the first general formula. Ethyl 6 - (3 - ethyl - 2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - ethylthio - 2 - cyano-2 : 4- hexadienoate is prepared by boiling together 2 - o  - acetanilidovinylbenzthiazole ethiodide and ethyl 2 - cyano - 3 - ethylthio - 2-butenoate in pyridine.  Ethyl 6-(3-methyltetrahydrothiazolylidene - 2) - 3 - ethylthio - 2 - cyano-2 : 4 - hexadienoate is prepared by fusing together 2-methylthiazoline and methyl p-toluenesulphonate, adding ethyl trithio orthoformate and boiling gently in acetic anhydride, distilling off the acetic anhydride in vacuo and dissolving the remaining oil in ethyl alcohol, adding ethyl 2 - cyano - 3 - ethylthio - 2-butenoate and triethylamine, and refluxing.  Ethyl 6 - (3 - methyl - 2 : 3 - dihydrobenzoxazolylidene - 2) - 3 - ethylthio - 2 - cyano - 2 : 4 - hexadienoate and the corresponding methyl ester, ethyl 6 - (3 - methyl - 2 : 3 - dihydrobenzthiazolylidene - 2) - 3 - methylthio - 2 - cyano - 2 : 4-hexadienoate, and the corresponding 3-ethylthio, 3 - isopropylthio, 3 - n - butylthio - and 3-benzylthio derivatives, the corresponding 3-ethyl derivatives, and the corresponding methyl 3-methyl, 3-methylthio and 3-ethylthio derivatives, ethyl 6 - (3 - ethyltetrahydrothiazolylidene - 2) - 3 - ethylthio - 2 - cyano - 2 : 4-hexadienoate, ethyl 6 - (3 - ethyl - 2 : 3 - dihydro-4 : 5 - benzbenzthiazolylidene - 2) - 3 - ethylthio-2 - cyano - 2 : 4 - hexadienoate and the corresponding 3-methyl, 3-methylthio and 3-ethylthio derivatives, ethyl 6-(3-methyl-2 : 3-dihydro-5-phenylbenzoxazolylidene - 2) - 3 - ethylthio - 2-cyano-2 : 4-hexadienoate and the corresponding 3-ethyl and 3-methylthio derivatives, ethyl 6-1 - ethyl - 1 : 2 - dihydroquinolylidene - 2) - 3-ethylthio - 2 - cyano - 2 : 4 - hexadienoate, ethyl 6 - (1 : 3 : 3 - trimethyl - 1 : 2 - dihydrindolylidene - 2) - 3 - ethylthio - 2 - cyano - 2 : 5 - hexadienoate, ethyl 6 - (2 - methyl - 2 : 3 - dihydro-6 : 7 - benzbenzthiazolylidene - 2) - 3 - ethylthio-2 - cyano - 2 : 4 - hexadienoate, ethyl 6 - (3-ethyl - 2 : 2 - dihydro - 5 : 6 - dioxymethylene benzthiazolylidene - 2) - 3 - ethylthio - - 2 cyano-2 : 4 - hexadienoate, ethyl 6 - (3 - methyl - 2 : 3-dihydro - 5 : 6 - dimethylbenzoxazolylidene - 2)-3 - methylthio - 2 - cyano - 2 : 4 - hexadienoate. and ethyl 6 - (1 - methyl - 1 : 2 - dihydroquinolylidene - 4) - 3 - methylthio - 2 - cyano - 2 : 4-hexadienoate are similarly prepared.  Similar dyes may be prepared from 2-methyl-selenazoline, -oxazoline, -benzselenazole, -pyrimidine, and -quinazoline.  Specification 642,514, [Group IV (b)], is referred to.