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
References
1Jung ME. Triphenylcarbenium Tetrafluoroborate In Encyclopedia of Reagents for Organic Synthesis
Vol.
8:
Parquette LA.
John
Wiley & Sons;
Chichester:
1995.
p.5348-5350
Scheme 1 Improved multi-gram preparation
of trityl fluoroborate