Process for the preparation of 2,2,3,3-tetrafluoro-1,4-benzodioxanes, novel o-(2-bromo-1,1,2,2-tetrafluoroethoxy)-phenols, and novel 2-bromo-1,1,2,2-tetrafluoroethoxy-containing phenyl ethers

A process for preparing a compound of the formula (I):

• ##STR59## where R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently hydrogen, halogen or C.sub.1-6 -alkyl, or where two adjacent radicals R.sup.1 to R.sup.4 together form a group of the formula --(CH.sub.2).sub.3 --, --(CH.sub.2).sub.4 --, or --(CH.sub.2).sub.5 -- or a group of the formula --CH.dbd.CH--CH.dbd.CH-- which is unsubstituted or substituted by halogen or C.sub.1-6 -alkyl, or
• where one or two of the radicals R.sup.1 to R.sup.4 may be nitro, cyano, --CO--R.sup.6 or --C(OR.sup.7).sub.2 R.sup.6, where R.sup.6 is hydrogen or C.sub.1-6 -alkyl and R.sup.7 is C.sub.1-6 -alkyl, or where R.sup.6 and R.sup.7 together form a group of the formula --CH.sub.2 CH.sub.2 --, --CH.sub.2 CH(CH.sub.3)--, --CH.sub.2 CH(C.sub.2 H.sub.5)-- or --CH(CH.sub.3)CH(CH.sub.3)--;
• which comprises the steps of:
• (a) reacting a compound of the formula (IV):
• ##STR60## wherein R.sup.1 to R.sup.4 are as above;
• and R.sup.5 is C.sub.1-6 -alkyl or benzyl;
• with 1,2-dibromo-1,1,2,2-tetrafluoroethane in the presence of an acid binder to obtain a compound of the formula (III);
• ##STR61## wherein R.sup.1 to R.sup.5 are as above;
• (b) subjecting said compound of the formula (III) to an ether cleavage to obtain a compound of the formula (II) ##STR62## wherein R.sup.1 to R.sup.4 are as above;
• and (c) cyclocondensing the compound of the formula (II) in the presence of an acid binder, optionally in the presence of a solvent, to obtain the compound of formula (I).