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In-Depth Information
Surprisingly tricyclic compounds can also be obtained in good yields and moderate ee.
Afterwards the same research group reported a Pauson-Khand reaction of
-unsaturated
aldehydes (such as acrolein) with alkynes in the presence of a bimetallic Co
2
Rh
2
catalyst
to afford the desired substituted cyclopentenones (Scheme 7.47).
81
,
O
O
Co
2
Rh
2
R
3
R
2
R
3
+
R
1
H
130
°
C, 18 h
R
1
R
2
48-77% yield
R
1
=H,Me,Ph
R
2
=H,Me,Ph
R
3
=TMS,C
5
H
11
,Bu,Ph
Scheme 7.47
Co
2
Rh
2
-catalyzed PK reaction of
α
,
β
-unsaturated aldehydes with alkynes.
7.8 Conclusion
This chapter illustrates the current evolution of the catalytic Pauson-Khand-type reaction
and the recent catalyst advances for these reactions. Although some significant improve-
ments have been achieved in intramolecular PK reaction, a path to the perfect intermolecular
PK reaction, especially with the elements of environmentally friendly, enantioselective and
low catalyst loading, is still a long way away. We believe the summary of the TON tables of
each type of catalysts provide useful information for readers to choose an appropriate cat-
alyst system in this reaction type for genuine synthetic applications. Further ligand (chiral)
designs are expected to be more practical this decade.
Acknowledgements
We thank the Research Grants Council of Hong Kong (GRF: PolyU 5014/10P), State
Key Laboratory of Chirosciences, European Commission (CATAFLU.OR), PolyU internal
funding (A-PA8R, G-U243), postdoctoral fellowship (G-YX1L) and the University Grants
Committee Areas of Excellence Scheme (AoE/P-10/01) for financial support.
References
[1] B. M. Trost,
Science
, 1991,
254
, 1471.
[2] For initial reports from Pauson and Khand, see: a) I. U. Khand, G. R. Knox, P. L.
Pauson, W. E. Watts,
J. Chem. Soc., Chem. Commun
. 1971, 36; b) I. U. Khand, G. R.
Knox, P. L. Pauson, W. E. Watts, M. I. Foreman,
J. Chem. Soc., Perkin Trans.
1
1973,
977.
[3] For reviews on PKR, see: a) H.-W. Fruhauf,
Chem. Rev.
1997,
97
, 523; b) O. Geis,
H.-G. Schmalz,
Angew. Chem.
1998,
110
, 955;
Angew. Chem. Int. Ed
. 1998,
37
,
911; c) N. Jeong, In
Transition Metals In Organic Synthesis: Building Blocks and
Fine Chemicals
, M. Beller, C. Bolm, Eds., Wiley-VCH: Weinheim, 1998, Vol. 1,
