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2005
Ring closure reactions
O 0130
Palladium(0)-Catalyzed Cyclization of Electron-Deficient Enynes and Enediynes.
The outcome of the cyclization concerning 1,6-enyne esters is found to depend on
06- 047 —
the nature of the educt as well as on the conditions used. For example, in the presence
of Pd2(dba)3 or PBN, the enyne ester (I) undergoes regioselective cyclodimerization.
Addition of phosphine ligands results in unusual formation of a 6-membered ring.
Under these conditions, the analogues (Ve) and (Vf) undergo normal cycloisomerization yielding the 5-membered ring systems (X) and (XI), respectively. A terminal ester
group as well as the presence of heteroatom in 1,6-enyne educts are found to be crucial
for successful cyclodimerization. Enediyne esters undergo [2 + 2 + 2]cycloisomerization to afford products of type (XV), (XVI), and (XVIII). — (YAMAMOTO*,
Y.; KUWABARA, S.; ANDO, Y.; NAGATA, H.; NISHIYAMA, H.; ITOH, K.; J. Org.
Chem. 69 (2004) 20, 6697-6705; Dep. Appl. Chem., Fac. Eng., Nagoya Univ.,
Chikusa, Nagoya 464, Japan; Eng.) — Jannicke
2005
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