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Synlett 2010(2): 333-334  
DOI: 10.1055/s-0029-1219042
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

Triphenylcarbenium Tetrafluoroborate

Huan Liang
Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
e-Mail: lianghuan@chem.ubc.ca;
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Publikationsdatum:
08. Januar 2010 (online)

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Introduction

Triphenylcarbenium tetrafluoroborate, also called trityl fluoroborate, is widely applied in organic reactions, [¹] such as dehydrogenation, [²] deprotection of ketone acetals, [³] alkyl ethers, [4] oxidation of silyl enol ethers, [5] preparation of cationic organometallics [6] or organic complexes, [7] as a polymerization catalyst [8] and as a Lewis acid catalyst. [9] Trityl fluoroborate is a yellow solid (mp 200 ˚C dec.), which is soluble in most organic solvents, e.g., dichloromethane, tetrahydrofuran, and reacts with nucleophilic solvents, e.g., water. Several preparation methods were described in the literature as early as the 1940s. Dauben et al. used triphenylcarbinol and 48% fluoroboric acid, while removing water from the reaction mixture by adding acetic anhydride. [¹0a] In 1972, Olah et al. developed a more convenient and economical route using trityl chloride and anhydrous tetrafluoroboric acid dimethyl etherate in dry benzene. [¹0b]

Scheme 1 Improved multi-gram preparation of trityl fluoroborate