SYNTHESES WITH THE REAGENT PENTAMETHYLCYCLOPENTADIENYL BROMIDE/SILVER TETRAFLUOROBORATE - THE PENTAMETHYLCYCLOPENTADIENYL CATION AS REACTIVE INTERMEDIATE

Jutzi P, Mix A. SYNTHESES WITH THE REAGENT PENTAMETHYLCYCLOPENTADIENYL BROMIDE/SILVER TETRAFLUOROBORATE - THE PENTAMETHYLCYCLOPENTADIENYL CATION AS REACTIVE INTERMEDIATE. CHEMISCHE BERICHTE-RECUEIL. 1992;125(4):951-954.Pentamethylcyclopentadienyl bromide 1 reacts with silver tetrafluoroborate with abstraction of the halide ion to form pentamethylcyclopentadienylium tetrafluoroborate (2). The 4-pi-antiaromatic cation in 2 can be trapped with different nucleophiles. Thus, 2 reacts with methanol to give 5-methoxy-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene (4). In the presence of methylamine, dimethylamine, or diethylamine, the corresponding pentamethylcyclopentadienyl-substituted amines 5, 6, and 9 are formed. Trapping of 1 with pyridine or dimethyl sulfide leads to the ionic compounds 7 and 8, respectively. The reaction of 2 with sterically crowded amines leads to tetramethylfulvene (3)