Tritylium cation

Alkenes in (alkene)dicarbonyl(T -cyclopentadienyl)iron(l+) cations react with carbon nucleophiles to form new C —C bonds (M. Rosenblum, 1974 A.J. Pearson, 1987). Tricarbon-yi(ri -cycIohexadienyI)iron(l-h) cations, prepared from the T] -l,3-cyclohexadiene complexes by hydride abstraction with tritylium cations, react similarly to give 5-substituted 1,3-cyclo-hexadienes, and neutral tricarbonyl(n -l,3-cyciohexadiene)iron complexes can be coupled with olefins by hydrogen transfer at > 140°C. These reactions proceed regio- and stereospecifically in the successive cyanide addition and spirocyclization at an optically pure N-allyl-N-phenyl-1,3-cyclohexadiene-l-carboxamide iron complex (A.J. Pearson, 1989). 

Cano, M.L., Cozens, F.L., Garcia, H., Marti, V. and Scaiano, J.C. (1996). Intrazeolite photochemistry. 13. Photophysical properties of bulky 2,4,6-triphenylpyrylium and tritylium cations within large- and extra-large-pore zeolites. J. Phys. Chem. 100, 18152-18157... 

Hydride abstraction of 1-(cycloprop-2-enyl)indenes and 9-(cycloprop-2-enyl)fluorenes 15 (obtainable by the reactions of 1,2-disubstituted cyciopropenylium ions and the indenyl or fluorenyl anion) with the tritylium cation, followed by treatment with tertiary amines, is one of the earliest calicene syntheses affording 1,2-benzocalicenes and 1,2 3,4-dibenzocalicenes 16. ... 

Quinocyclopropenes containing a thienoquinone (27) and a methano[10]annulenequinone (28) moiety were synthesized in similar but modified ways, i.e. addition of chlorophenylcarbene to stilbene analog 25, dchydrochlorination with potassium tert-butoxide to cyclopropene 26, hydride abstraction and deprotection with tritylium cation, and finally base treatment provided... 

Hydride abstraction from 1,3-dialkyl-2-chlorocyclopropenes with one equivalent of tritylium tetrafluoroborate in dichloromethane at 0 C resulted in complete conversion to the chloro-cyclopropenylium cations. Treatment of the cation solutions with saturated sodium hydrogen carbonate afforded cydopropenones. 

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