Tropylium tetrafluoroborate, 97%, Thermo Scientific Chemicals

General References:

1. Markku Lämsä; Kirsi Raitamaa andJouni Pursiainen. Synthesis of podands bearing aromatic end groups and complex formation with tropylium tetrafluoroborate in 1,2-dichloroethane. Journal of Physical Organic Chemistry. 1999, 12 (7), 557-563.
2. Stanisław Ostrowski and Mieczysław Mąkosza. Reactions of Organic Anions, 160. Synthesis of Heptafulvene Derivatives by Vicarious Nucleophilic Substitution of Hydrogen in Tropylium Tetrafluoroborate. Environ. Sci. Technol. 1989, 1989 (1), 95-97.
3. Interesting non-benzenoid aromatic system. For a review of 7-membered conjugated cyclic systems, see: Chem. Rev., 73, 293 (1973).
4. Reaction with a variety of nucleophiles leads to 7-substituted heptatrienes, e.g. active methylene compounds: Bull. Chem. Soc. Jpn., 50, 3425 (1977); J. Org. Chem., 42, 401 (1977), and organometallic reagents: Bull. Soc. Chim. Fr. 2, 127, 245 (1990).
5. Undergoes [3+2]-cycloaddition with allenylsilanes, in the presence of a non-nucleophilic acid scavenger, in a general route to azulenes: J. Am. Chem. Soc., 111, 389 (1989):
6. Propargylsilanes react similarly: J. Org. Chem., 57, 6094 (1992).
7. For reduction to bitropyl (7,7'-bi-cycloheptatrienyl) by one-electron donating reagents such as low-valent Ti or V, see: Synthesis, 798 (1976).