Chemistry Reference
In-Depth Information
Another variation of the oxidation reaction with dioxygen can be e
ciently accom-
plished by a catalytic condensation of amines and isonitriles using a palladium
complex catalyst and iodine at 100
C to give dialkylcarbodiimides in yields of 35-
86% [1283]. Dicyclohexylcarbodiimide was obtained in 67% yield from cyclo-
hexylisonitrile 1748 and cyclohexylamine 1749 (see Section 4.5.3.5, Table 4.48).
1.
Pd(OAc)
2
I
2
, Na
2
CO
3
MeCN
H
2
N
+
N
N
NC
2.
O
2
(40 psi)
100°C, 3 h
67 %
DCC
1748
1749
Typical procedure. Dicyclohexylcarbodiimide DCC [1283]:
Palladium acetate (22 mg,
0.1 mmol), iodine (50 mg, 0.2 mmol), and anhydrous sodium carbonate (320 mg,
3.0 mmol) were placed in a pressure vessel. Cyclohexylamine (0.11 mL, 1.0 mmol)
and cyclohexyl isocyanide (0.1 mL, 0.8 mmol) were dissolved in acetonitrile (10
mL) and this solution was added to the reaction vessel, which was then pressurized
with oxygen (40 psi) and heated to 100
C for 3 h. The initially deep-red reaction
mixture turned yellow-orange; no Pd black precipitation was observed. There was
no obvious reaction rate dependence on oxygen pressure. The mixture was cooled
to ambient temperature, depressurized, filtered, and analyzed by GC. DCC was
isolated by evaporating the solvent and residual amine, followed by vacuum distil-
lation.
Palladium(II) complexes with a carbodiimide ligand, in which a nitrogen of the
linear N
N moiety is bonded to the metal center, and bis(carbodiimido)palla-
dium(II) complexes, both derived from isocyanides, have been described [1284].
b
C
b
4.5.3.5
Dicyclohexylcarbodiimide (DCC)
Dicyclohexylcarbodiimide (DCC) is the most widely used carbodiimide and many
efforts have been made to produce it e
ciently. Recent publications and patents
are presented in Table 4.48.
A new field of application for DCC has been entered with carbodiimide-mediated
multicomponent reactions (MCRs). 4-Thiazolidinones 1697 have been assembled by
a 3CR of amine 1694, aldehyde 1695, and mercaptoacetic acid 1696, mediated by
DCC, in yields of 54-95% within 1 h at room temperature [1251].
O
DCC
O
OH
N
S
+
+
RNH
2
R´
H
S
R
54-95 %
1697
H
THF
rt, 1 h
O
1694
1695
1696
R´
R = benzyl, phenyl, cyclohexyl, n-butyl, n-octyl, i-propyl, CH(CH
2
Ph)CO
2
Me
R´= phenyl, 4-chlorophenyl, 2-methoxyphenyl, 1-naphthyl, 4-cyanophenyl
