REACTION OF CYCLOPROPYLBENZENE AND CYCLOPROPYL PHENYL KETONE WITH SULFUR-TRIOXIDE

The sulfonation of cyclopropylbenzene (1a) and cyclopropyl phenyl keto ne (5) with sulfur trioxide in both nitromethane and 1,4-dioxane as so lvent has been studied. Sulfonation of cyclopropylbenzene (1a) with up to 2.0 mol-equiv. of SO3 in dioxane leads to the initial formation of 3-phenyl-1,3-propanesultone (2a) which product subsequently slowly is omerizes to 3-phenyl-2-propene-1-sulfonic acid (4a). Sulfonation of 1a with 4.0 mol-equiv. of SO3 in nitromethane gives the corresponding 4- sulfo derivatives 2b and 4b, of which the former product also slowly i somerizes to give the latter. Reaction of cyclopropyl phenyl ketone (5 ) with SO3 in nitromethane yields quantitatively 1-benzoyl-1,3-propane sultone (6). Upon aqueous alkaline work-up of the reaction mixtures, t he gamma-sultones 2a and 6 are quantitatively converted into the corre sponding potassium hydroxypropanesulfonates 3 and 7, respectively. Mec hanisms for the formation of the various products from the starting cy clopropyl substrates are proposed.