Hydantoine, thiohydantoine, glykocyamidine—XXXIII : Durch Lewis-säuren ausgelöste reduktive umlagerungen vom retrobenzilsäure-typ—VIII reaktionen einiger 5,5-diarylthiohydantoin-derivate mit bortrifluorid-ätheraten, bortrifluorid-ätherat/ bortrifluorid-gemischen und galliumbromid

Abstract

5,5-Diaryldithiohydantoins of type 1b, when refluxed with BF 3 dimethyl etherate or mixtures of the former reagent with BF 3 in toluene or chlorobenzene, are selectively methylated at the S(2) atom, and/or suffer rearrangement of the retrobenzilic acid type under simultaneous extrusion of the thioxo sulfur atom from position 4 to yield imidazole derivatives of type 6. The latter type of reaction was previously brought about by aluminium chloride. Derivatives already methylated at the S(2) atom are only rearranged, as are also the derivatives of 5,5-diphenyl-4-thiohydantoin ( 1a, R′ ▪ R″ ▪ H) if a reaction with the latter occurs at all. Derivatives of 5,5-diphenyl-2-thiohydantoin, on the other hand, are only S-methylated by boron trifluoride dimethyl etherate without being rearranged. The selective methylating properties of the BF 3 dimethyl etherate reagent may be applied for the smooth preparation of several hitherto difficulty accessible (di)thiohydantoin derivatives. Gallium tribromide proved to be a catalyst comparable with aluminium trichloride for effecting rearrangements of 5,5-diaryl-4-thio- and -dithiohydantoin derivatives, its milder properties being in some cases favourable. In the cases where the migratory aptitudes of phenyl and p-chlorophenyl groups could be compared, the migratory aptitude of the former was always the greater.