Process for the preparation of substituted difluorobenzo-1,3-dioxoles

A compound of formula Ia ##STR30## wherein R.sup.1 is --OH, --SH, --CN, --COOH, --B(OH).sub.2, --COX, with X being Cl or Br, or is --COOR.sup.2, --SiR.sup.2.sub.3 or --C(OR.sup.2).sub.2, with R.sup.2 being a C.sub.1 -C.sub.12 alcohol moiety without the hydroxy group, wherein R.sup.1 is further --C.sub.n H.sub.2n COOR.sup.2, with n being an integer from 1 to 4, or linear or branched C.sub.1 -C.sub.12 hydroxyalkyl which is unsubstituted or is substituted by --F, --CN, C.sub.1 -C.sub.6 alkoxy, phenyl, fluorophenyl, C.sub.1 -C.sub.4 alkoxyphenyl, C.sub.1 -C.sub.4 alkylthiophenyl, C.sub.1 -C.sub.4 alkylphenyl, C.sub.1 -C.sub.4 fluoroalkyl-phenyl, nitrophenyl or by cyanophenyl, or wherein R.sup.1 is a benzyl alcohol which is unsubstituted or is substituted by F, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkylthio, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 fluoroalkyl, nitro or by cyano, or is C.sub.2 -C.sub.12 acyl, or wherein R.sup.1 is a radical of formula II ##STR31## wherein R.sup.5 is --CN, --CF.sub.3, --COOR.sup.2, --CONH.sub.2, --CO--NHR.sup.2 or --CONR.sup.2.sub.2, R.sup.3 and R.sup.4 are a direct bond or each is H, or R.sup.3 is H and R.sup.4 independently has the meanings of R.sup.5, the radical of formula II is not --CH.dbd.CH--CN.