ORGANIC
LETTERS
2005
Vol. 7, No. 8
1657-1659
Thioureas as Ligands in the
Pd-Catalyzed Intramolecular
Pauson−Khand Reaction
Yefeng Tang,† Lujiang Deng,† Yangdong Zhang,† Guangbin Dong,†
Jiahua Chen,*,† and Zhen Yang*,†,‡
Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of
Education, College of Chemistry, Beijing 100871, China, Laboratory of Chemical
Genetics, Shenzhen Graduate School of Peking UniVersity, The UniVersity Town,
Shenzhen 518055, China, and ViVoQuest, Inc., 711 ExecutiVe BlVd.,
Valley Cottage, New York 10989
Received February 24, 2005
ABSTRACT
The thiourea−Pd complex was established as a novel type of catalyst in the PKR of allylpropargylamine, and the demonstrated chemistry may
prove to be valuable for developing thiuorea as a ligand for the Pd-catalyzed Pauson
−Khand reaction.
The Pauson-Khand reaction1 (PKR) is utilized as an
effective method to construct cyclopentenone frameworks
in the synthesis of many complex molecules,1b-d such as (+)-
epoxydictymene.2 Catalytic PKRs with the use of Co,3 Ti,4
Ni,5 Ru,6 Rh,7 and Ir8 complexes have been reported in the
past decade; however, no successful example of the Pd-
catalyzed PKR is currently known.9
Recently we reported tetramethyl thiourea (tmtu) as an
effective additive in the Co-catalyzed PKR.10 In view of a
lack of any precedents in the utilization of palladium as a
catalyst in the PKR, we decided to apply thioureas in the
Pd-catalyzed PKR. We now report herein our preliminary
results on the Pd-catalyzed PKR using thioureas as effective
ligands.
† Peking University.
‡ VivoQuest, Inc.
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10.1021/ol050410y CCC: $30.25
© 2005 American Chemical Society
Published on Web 03/15/2005