Dimethine dyestuffs, their preparation and their use for dyeing synthetic and natural materials

A styryl dyestuff of the formula ##STR25## in which R is a lower alkyl or alkenyl group which can be substituted by a non-ionic radical,

• R.sup.3 is a C.sub.1 - to C.sub.4 -alkyl, which can be substituted by phenyl or C.sub.1 - to C.sub.4 -alkoxycarbonyl, C.sub.3 - or C.sub.4 -alkenyl, which can be substituted by phenyl, C.sub.2 - to C.sub.4 -alkyl, which is substituted by one hydroxyl, C.sub.1 - to C.sub.4 -alkoxy, phenoxy, benzyloxy, benzoyloxy, benzamido, phenylsulphamido, mesylamino, C.sub.1 - to C.sub.3 -alkylcarbonyloxy, C.sub.1 - to C.sub.4 -alkylcarbamoyloxy, phenylcarbamoyloxy, chlorine or cyano radical, or C.sub.3 - or C.sub.4 -alkyl, which is substituted by one or two hydroxyl, methoxy, ethoxy, acetoxy or chlorine radicals, it being possible for the phenyl radicals in turn to be substituted by one hydroxyl, C.sub.1 - to C.sub.4 -alkoxy, C.sub.1 - to C.sub.4 -alkoxycarbonyl, C.sub.5 - or C.sub.6 -cycloalkyl, benzyl, 2-phenylprop-2-yl, phenoxy, benzyloxy, phenylmercapto, phenylsulphonyl, nitro or cyano radical or by 1 to 3 fluorine, chlorine, bromine or C.sub.1 - to C.sub.4 -alkyl radicals,
• W.sup.1, W.sup.2, W.sup.3 and W.sup.4 each independently is hydrogen or C.sub.1 - to C.sub.4 -alkyl, and
• W.sup.1 can also represent phenyl,
• W.sup.3 can also represent chlorine,
• W.sup.1 and W.sup.3 together can form the remaining members of a cyclohexane ring, or
• W.sup.3 and W.sup.4 together can form the remaining members of a cyclopentane or cyclohexane ring,
• Z is O, S, N-W.sup.5 or ##STR26## m is 0, 1 or 2, W.sup.5, W.sup.6 and W.sup.7 each independently is H or C.sub.1 - to C.sub.4 -alkyl,
• ring B can be substituted by C.sub.1 - to C.sub.4 -alkyl, and
• An.sup.- is an anion.