Switch from palladium-catalyzed cycloisomerization/dimerization of terminal allenyl ketones to preferential formation of monomers by a 5-palladatricyclo[4.1.0.02,4]heptane catalyst: synthesis of furans from substrates incompatible with the commonly used silver catalysts - Hashmi, A. Stephen K.; Schwarz, Lothar (Chemische Berichte - recueil, 1997)