Thiomethylated benzofuran-2-ones

A compound of formula (1) ##STR10## wherein R.sub.1 is phenyl or phenyl which is substituted by C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.18 alkoxy, C.sub.3 -C.sub.18 alkenyloxy, benzyloxy, C.sub.1 -C.sub.18 alkanoyloxy, hydroxy or halogen,

• R.sub.2 and R.sub.4 are each independently of the other hydrogen or C.sub.1 -C.sub.4 alkyl, or R.sub.4 and R.sub.5, together with the linking carbon atoms, form a phenyl ring, and
• R.sub.3 and R.sub.5 are each independently of the other a radical of formula --CH.sub.2 --S--R.sub.6, wherein R.sub.6 is C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.8 cycloalkyl, benzyl, phenyl or a radical of formula --CH.sub.2 --CO.sub.2 R.sub.7 or --C.sub.2 H.sub.4 --O--R.sub.8, wherein R.sub.7 is hydrogen or C.sub.1 -C.sub.18 alkyl and R.sub.8 is hydrogen or C.sub.2 -C.sub.19 alkanoyl.