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46.5.5.1.1 Variation 1: Palladium-Catalyzed Cycloisomerization

DOI: 10.1055/sos-SD-046-00090

Gandon, V.; Thorimbert, S.; Malacria, M.Science of Synthesis, (200946228.

The palladium-catalyzed cycloisomerization of 1,6- and 1,7-enynes into 1,3-dienes having endocyclic and exocyclic double bonds was first reported in 1994.[‌187‌] For example, both the cyclopentene 192 and the cyclohexene 193 can be synthesized from the 1,6-enyne 190 in good yields. The ligand bonded to the palladium atom is responsible for the chemical course of the reaction. Thus, in the presence of the ligand 1,3-bis(diphen­ylphosphino)propane isomerization of the initially formed 1,2-bis(methylene)cyclopentene 191 affords the cyclopentene 192 (Scheme 68), a result that has been confirmed during studies directed at the synthesis of cyclic amino acids.[‌188‌] The use of a catalytic system composed of palladium(II) acetate (40mol%) and tri-2-tolylphosphine (80mol%) in acetic acid/acetonitrile can be utilized for the preparations of macrocyclic peptides, but yields are moderate.[‌189‌]

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