FLUOROCYCLISATION OF 2,5-TETRAHYDROFURANDICARBOXYLIC AND 2,3,4,5-TETRAHYDROFURANTETRACARBOXYLIC ACIDS WITH SULFUR-TETRAFLUORIDE LEADING TO BICYCLIC AND TRICYCLIC FLUOROETHERS

cis-2,5-Tetrahydrofurandicarboxylic acid (1) reacts with sulphur tetra fluoride to give comparable amounts of 2,5-bis(trifluoromethyl) tetrah ydrofuran (2) and the bicyclic tetrafluoroether, 2,2,4,4-tetrafluoro-3 ,8-dioxa-bicyclo [3.2.1]octane (3). Cyclisation of cis-2,5-carboxylic groups leading to the tricyclic fluoroethers, ,8,9,9-octafluoro-4,10-d ioxatricyclo[5.2.1.01(,7)] decane (6) and ,10-octafluoro-4,9,11-trioxa tricyclo[5.3.1.0(1,7)] undecane (9) was also found to be the main or e quivalent course of the reactions of rafluoroethano-cis-2,5-tetrahydro furandicarboxylic acid ( 4) and trans,cis, trans-2,3,4,5-tetrahydrofur antetracarboxylicacid (7); the bis(trifluoromethyl) derivatives, (trif luoromethyl)-6,6,7,7-tetrafluoro-3-oxabicyclo [3.2.0]heptane (5) and e xo-cis-2,4-bis(trifluoromethyl) -6,6,8,8-tetrafluoro-3,7-dioxabicyclo [3.3.0]heptane (8) are formed in lower or comparable amounts. (C) 1997 Elsevier Science S.A.