Chemistry Reference
In-Depth Information
Tab l e 9 . 8
Substrate
Product
Yield (%)
R
R
Z
Z
O
Z
R
C(CO
2
Et)
2
O
NTs
Ph
Bu
Me
97
85
87
O
+
R
R
R
Bu
Ph
64
65
O
+
49
Ph
Ph
O
+
Ph
Ph
17
The screening result of various enyne substrates for the intramolecular PKR under optimized
reaction conditions (
Co
2
Rh
2
/C (0.05 g), enyne (0.96 mmol), crotonaldehyde (2.4 mmol),
THF, 130
◦
C, and 18 h) is shown in Table 9.8. The catalytic system is effective for giv-
ing high yields of the intramolecular PKR products. No additives were necessary to en-
hance or promote the catalytic reaction. Moreover, multi-gram quantities of cyclopen-
tenones were obtained without any difficulties. The catalytic system is also effective in
the intermolecular PK-type reaction although the yields were not high, partly due to
the trimerization of alkynes. For example, in a reaction of phenylacetylene with nor-
bornene, the PKR product and trimerization product were obtained in 64% and 23% yields,
respectively.
9.4.2.3
Co
2
Rh
2
-catalyzed asymmetric catalytic Pauson-Khand-type reaction
13
Compared to the huge advances seen in homogeneous asymmetric catalysis, most of the
transition metal nanoparticle-catalyzed reactions have been limited to non-asymmetric
reactions
39
until the advent of some notable reports.
15d,40