Key points are not available for this paper at this time.
Enantioenriched five-membered rings with a quaternary chiral center are prepared with remarkable efficiency by the ene-type carbocyclization of 1,6-enynes catalyzed by chiral palladium complexes (see scheme). Possible mechanisms including neutral (five-coordinate) and cationic (four-coordinate) intermediates have also been proposed.
Hatano et al. (2001) studied this question.