Intermolecular and intramolecular pauson-khand reactions of functionalized allenes

Pauson-Khand reactions of functionalized allenes with different alkynes give cyclopentenones with generally high regio- and stereoselectivities. The allenes react through their external double bonds, giving cyclopentenones with exocyclic double bond at their P positions and predominantly with E stereochemistry. Some intramolecular reactions with allenynes connected through aromatic rings are described. These give the corresponding heterocycles with moderate to good yields. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).