SULFONATION OF TRANS-10B,10C-DIMETHYL-10B,10C-DIHYDROPYRENE AND ITS 2,7-DI-TERT-BUTYL DERIVATIVE WITH SULFUR-TRIOXIDE

The sulfodeprotonation of trans-10b,10c-dimethyl-10b, 10c-dihydropyren e (1) with sulfur trioxide has been studied in dioxane as solvent, as well as in dichloromethane, using 4.0-5.0 equivalents of dioxane relat ive to the amount of SO3 as reactivity moderator. Reaction of 1 with 0 .6 mol-equiv. of SO3 in dioxane at 22 degrees C yields initially only the 2- and 4-sulfonic acid in a 84/16 ratio. Using 3.0-6.0 mol-equiv, of SO3 in dichloromethane with the temperature increasing from -78 up to 22 degrees C the initially very rapid formation of the 1-, 2- and 4 -sulfonic acid (formed in a ratio of 11/82/7) is followed by a much sl ower conversion into a mixture of 1,7-, 2,4-, 2,5- and 2,7-disulfonic acid. These four acids are subsequently converted even more slowly int o a mixture of the 1,4,7-, 2,4,7- and 2,5,9-trisulfonic acids to yield in part the 1,4,7,9-, 2,4,7,9- and 2,4,7, 10-tetrasulfonic acids. tra ns-2,7-Di-tert-butyl-10b, 10c-dimethyl-10b,10c-dihydropyrene (2) with 0.8-2.0 equiv. of SO3 in dioxane as solvent gives the 4-sulfonic acid which is slowly converted into a 16/84 mixture of the 4,9- and 4,10-di sulfonic acids. The observed distributions of sulfonic acid isomers ar e discussed in terms of the directing effects of the ''ideal'' - almos t planar - [14] annulene and the sulfo and/or tert-butyl substituent(s ) already present.