Page 110 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements

GROUP 13 ELEMENTS
90
The first steps of the mechanism are standard for electrophilic aromatic substitution:

O F 3 C
O O +
O +
C TI O O −
F 3 − CF CO
− H 3 2 O O
O F C TI H
3
O CF TI
O O O 3
F C O O CF 3
3
F C
3
O
F C
3
+
+
O O − H O O
H
TI TI
F C O O CF 3 F 3 C O O CF 3
3
(3.48)
The thallated benzene is a valuable synthetic intermediate. With two equivalents of potas-
sium iodide, it provides a convenient route to aromatic iodides, as shown below:

O O O
O
TI −
C O O F 3 C
F 3 CF 3 O TI
− I O CF 3
I

− O −
I − CF CO 2
3
TI
C O I TI
F 3 I
− I
I

+ TI I
TI I
I I
(3.49)
The first part of the above mechanism is unremarkable, consisting of simple nucleophilic
substitutions. The last step is more interesting: it’s a reductive elimination, where trivalent
thallium is reduced to monovalent.