Cross-coupling for cross-conjugation: Practical synthesis and Diels-Alder reactions of [3]dendralenes

(Chemical Equation Presented) The parent [3]dendralene and 2-substituted [3]dendralenes are made easily through cross-coupling reactions. Contrary to some earlier reports, [3]dendralene is sufficiently stable to be handled using standard synthetic methods. These compounds allow the one-step stereoselective construction of polycyclic frameworks through reactions with dienophiles. Site selectivity and stereoselectivity in Diels-Alder reactions with dienophiles are generally not influenced by the nature of the [3]dendralene's 2-substituent; these features can, however, be influenced with Lewis acids. © 2007 American Chemical Society