Introduction <P>Phenyltrimethylammonium tribromide (PTAB) is known to be a convenient
oxidizing and brominating agent. It is an orange crystal and easy
to handle, with a melting point at 113-115 ˚C.
[
¹ ]
It has been used for the
oxidative transformation of
trans -stilbene
oxide to 2-phenyl-1,3-dioxane in the presence of various of 1,3-diols
and a catalytic amount of SbBr
3 ,
[
² ]
for
brominating the α-position of carbonyl compounds,
[
³-8 ]
α′-bromination
of α,β-unsaturated ketones,
[
9 ]
and
for the addition of bromine to alkenes.
[
¹0 ]
It was
also found to be useful for the chemoselective conversion of 3-alkoxyfurans
to 2-alkoxy-3(2
H )-furanones, oxidative
ring-opening of 3-alkoxy-2,5-diphenylfurans to cis-2-alkoxy-2-butene-1,4-diones,
[
¹¹ ]
and synthesis
of imidazolines,
[
¹² ]
3-bromo-2-styrylchromones,
[
¹³ ]
nitro dibromo-phenols,
[
¹4 ]
pyridazines,
[
¹5 ]
phytoalexin cyclobrassinin,
[
¹6 ]
p -bromodienone
calixarene derivatives,
[
¹7 ]
and
2-arylthiazino[5,6-
b ]indoles.
[
¹8 ]
</P><P>Phenyltrimethylammonium tribromide is commercially available
now. It can be readily prepared from
N,N -dimethylaniline
and dimethyl sulfate, followed by treatment with 48% hydrobromic
acid and bromine.
[
¹ ]
</P>
Scheme 1
