,
2001, 11(5), 172–173
Xenon difluoride–trimethylsilyl isocyanate–triflic acid as a new system for the
amination of aromatic compounds
Namig Sh. Pirkuliev,a,b Valery K. Brel,* Novruz G. Akhmedov, Nikolai S. Zefirov and Peter J. Stangc
a
b
a,b
a
Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, 142432 Moscow region,
b
Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation
Department of Chemistry, Unversity of Utah, Salt Lake City, UT 84112, USA
c
1
0.1070/MC2001v011n05ABEH001514
+
–
In the title system, OCNXeOSO CF is formed, which readily oxidises iodobenzene to [PhI –NCO OTf]. The direct amination of
2
3
aromatic substrates is possible with the use of XeF –Me SiNCO–CF SO H.
2
3
3
3
Since the discovery of the first xenon compounds by Bartlett1
in 1962, a large number of xenon derivatives with Xe–F, Xe–Cl,
Xe–O, Xe–N, Xe–C and Xe–N bonds were prepared.2 The
methodology of Xe–element bond formation is based on the rup-
ture of M–element bonds (where M = Bi, Sb or Si) with the aid
of xenon fluorides. The Si–element fission bond is most promising
CF SO O
3
2
IC6H5
I
I
4
H N
2
I
2
(a),3
i, Me SiNCO
3
ii, CF3SO2OH
and interesting for obtaining compounds with Xe–N bonds.
I
3
(c)
Thus, D. D. DesMarteau used this approach for the prepara-
tion of the relatively stable compound FXe(NSO F) . Recently,
XeF2
NH2
2
2
5
6
theoretical computations and product analysis of the reaction of
XeF with NaN and NaOCN indicated the intermediate forma-
2
3
R
4
tion of FXeN and FXeNCO.
3
R'
R
H N
2
Previously, we found that the reaction of trimethylsilyl iso-
cyanate with XeF or FXeOSO CF in the presence of olefins
RR' C6H4
2
2
3
R'
NH2
proceeds through the formation of FXeNCO and OCNXeOSO CF3
2
intermediates, which are easily added at the double bond of an
olefin. In a continuation of this work, we studied the interaction
7a–d
8a–d
a R = R' = H
of trimethylsilyl isocyanate with XeF or FXeOSO CF in the
2
2
3
b R = Cl, R' = H
c R = Me, R' = H
d R = R' = Me
presence of aromatic compounds. It is well known that, in this
case, the reaction path strongly depends on the order in which
the reactants were added. In particular, if finely dispersed XeF2
Scheme 2
5
in CH Cl was transformed into FXeOTf and the latter was
2
2
treated with trimethylsilyl isocyanate and then with iodobenzene,
mixed iodonium sulfonate 3 was obtained.
instead of iodobenzene the formation of amines 7 and 8 takes
place (Table 1).
6
†
Table 1 Amination of aromatic compounds with XeF –Me SiNCO–CF SO H.
CH Cl2
Me SiNCO
2
3
3
3
2
3
XeF2 + HOTf
FXeOTf
–
TMSF
Reaction Yielda
ortho-
para-
Yield of 4
a
1
Substrate
C H
time/h
(%)
isomer
isomer
(%)
PhI
–
–
+
[
Xe(OTf)(NCO)]
TfO PhI –NCO
Xe
3
3
4
6
3
45
40
38
35
43
—
54
50
45
—
6
6
2
3
MeC H
46
44
48
—
Scheme 1
6
5
IC H
44
6
5
When trimethylsilyl isocyanate was added to a XeF solution
in CH Cl and the resulting mixture was subsequently treated
with triflic acid and iodobenzene, phenyl(p-iodophenyl)iodonium
triflate 4 and iodoanilines 5, 6 (as a mixture of ortho and para
isomers) were isolated from the reaction mixture as a final pro-
ClC H
2
6 5
o-Xylene
2
2
a
Isolated yields based on XeF used.
2
‡
Reaction of iodobenzene with XeF –Me SiNCO–HOTf. XeF (4.72 mmol)
2
3
0
2
1
‡
was dissolved in dry CH2Cl2 (15 ml) under argon; then, Me3SiNCO
5.1 mmol) was added. Triflic acid (10 mmol) was slowly added dropwise
at –78 °C to the solution of FXeNCO in dry CH Cl and then the mix-
ducts. Note that in this case the formation of compound 3 was
(
not detected.
2
2
Consequently, the XeF –Me SiNCO–CF SO H system acts
2
3
3
3
ture was stirred at –30 °C for ~1 h. Then, a large excess of PhI (12 mmol)
was added to the suspension at –78 °C, and the mixture was stirred until
no more gas (Xe) was evolved (see Table 1 for total reaction time). The
solution was heated to room temperature and poured into a dilute solu-
tion of HCl with ice. An excess of iodobenzene and phenyl(p-iodophenyl)-
iodonium triflate 4 were extracted with dichloromethane (3×15 ml). The
volatile materials were then removed under reduced pressure to give an
oily residue, which was dissolved in dry diethyl ether. The mixture was
vigorously shaken for several minutes to precipitate slightly coloured
crystals. Analytically pure samples were obtained by recrystallization from
CH Cl –Et O. The aqueous layer was neutralised with a 30% sodium
7
,8
as an aminating reagent for aromatic compounds.
Moreover, we found that with the use of other aromatic com-
pounds such as benzene, toluene, chlorobenzene and o-xylene
†
+
–
Typical procedure for the preparation of [PhI NCO OTf]. 5.52 mmol
of Me SiNCO was added to a stirred suspension of 4.72 mmol of
3
5
CF SO OXeF in 20 ml of CH Cl at –78 °C under argon. The mixture
3
2
2
2
was allowed to warm up to –40 °C and stirred until the formation of a
yellow homogeneous solution. The solution was cooled to –78 °C; then,
.72 mmol of iodobenzene was added using a syringe. The mixture was
4
2
2
2
allowed to warm to –5 °C and stirred for ~2 h. The precipitate was fil-
tered off under argon, washed with cold diethyl ether and dried in vacuo
to yield the material of >98% purity. The analytically pure compound
can be obtained by recrystallization from CH Cl –Et O.
hydroxide solution to pH ~13. The mixture of o- and p-iodoanilines 5, 6
was then extracted with dichloromethane and dried with MgSO . Pro-
4
ducts were isolated after evaporating the solvent. Isomeric mixtures were
1
analysed by H NMR.
2
2
2
3
1
[
Isocyanato(trifyloxy)-l -iodo]benzene 3. H NMR (CD CN) d: 8.3–7.5
Phenyl(p-iodophenyl)iodonium triflate 4: yield 44%, mp 146–147 °C
3
13
11
1
(
m). C NMR (CD CN) d: 172.5 (CO), 136.6, 135.0, 132.9, 122.7 (Ph),
(lit., 144–148 °C). H NMR (CDCl ) d: 7.48 (m, 2H, Ph), 7.64 (m, 1H,
3
3
1
20.8. 19F NMR (CD CN) d: –78.6 (CF ). IR (CCl , n/cm ): 2510, 1625
–1
Ph), 7.80 (m, 4H, C H ), 8.10 (m, 2H, Ph). F NMR (CDCl ) d: –78.4
19
3
3
4
6
4
3
(NCO), 1258, 1178, 1023 (OTf).
(CF SO ).
3 3
–
172 –
Pirkuliev
