Direct syntheses of polyfused ring systems by intramolecular tandem palladium-ene/Heck insertion reactions
摘要:
The Pd(0)-catalyzed polycyclizations 1 --> 3 + 4, 5 --> 9 and 6 --> 10 are described. The stereospecifity of these transformations is ascribed to an intramolecular suprafacial "palladium-ene" process followed by one to two "Heck-insertions" proceeding with retention of configuration at the metalated carbon.
Direct syntheses of polyfused ring systems by intramolecular tandem palladium-ene/Heck insertion reactions
摘要:
The Pd(0)-catalyzed polycyclizations 1 --> 3 + 4, 5 --> 9 and 6 --> 10 are described. The stereospecifity of these transformations is ascribed to an intramolecular suprafacial "palladium-ene" process followed by one to two "Heck-insertions" proceeding with retention of configuration at the metalated carbon.
Catalytic cycloisomerization of enynes has been accomplished in the presence of an Ni0-PPh3-Zn-carboxylic acid or -ZnCl2 system. A nickel(I)-hydride complex, thought to be generated by reduction of the protonated nickel(II) complex with Zn, is proposed as the catalytic species. This cycloisomerization shows reactivity behavior that is different from that of a conventional metal-catalyzed reaction. In particular