Formation of 1,1,3,3-tetrafluoro-1,3-dihydroisobenzofurans in reactions of phthalic acids with sulphur tetrafluoride. Evaluation of the steric and electronic effects of the substituents

Article abstract of DOI:10.1016/S0022-1139(00)80485-6

4,5-Dinitrophthalic acid and 3,6-dimethylphthalic anhydride have been reacted with sulphur tetrafluoride to give mixtures of the corresponding bis(trifluoromethyl)benzenes and 1,1,3,3-tetrafluoro-1,3-dihydroisobenzofurans in a 5:1 and 1:3.6 ratio, respectively.These and earlier results on the reactions of sulphur tetrafluoride with substituted and unsubstituted phthalic and pyromellitic acids are compared and structural factors in the acids influencing the competitive formation of cyclic and non-cyclic products discussed.The stability of 1,1,3,3-tetrafluoro-1,3-dihydroisobenzofurans against cleavage by anhydrous hydrogen fluoride has also been investigated.