UNUSUAL REACTIONS IN MOLECULES WITH CROWDED FUNCTIONAL-GROUPS - SULFONAMIDE REDUCTION UNDER OXIDIZING CONDITIONS IN CAMPHOR DERIVATIVES

The reaction of the camphor-derived dialkyne 1 with polarizable compou nds like acids and halogens leads to the formation of cationic species of the type 2 with a pentacyclic structure. These are stable in trifl uoroacetic acid, but undergo reduction of the sulfonamide to a sulfina mide group in other solvents. The reaction mechanism was studied by NM R measurements, With iodine as reagent, further reactions occur due to the low stability of the carbon-iodine bonds, leading to the introduc tion of a carbonyl group into the newly formed carbocyclic ring. The c rystal structure of the acetate derivative 8 shows that the reduction of the sulfonamide group occurs stereoselectively, leading to the S-co nfiguration of the sulfur atom in the sulfinamide. This configuration can be inverted by strong acids, In addition, reduction of the sulfina mides to a sulfenamide was observed in the reaction mixture with iodin e.