Synthesis of 4-Aryl- and 4-Alkyl-2-silyl-1,3-butadienes and Their Diels−Alder/Cross-Coupling Reactions

An ene-yne cross methasis of silyl-substituted alkynes and alkenes has been developed as a route to 4-aryl- and 4-alkyl-2-silyl-substituted 1,3-dienes. The dienes prepared were used to affect highly diastereoselective Diels−Alder reactions and then the silicon-substituted Diels−Alder cycloadducts were used in Hiyama cross-coupling reactions. The cross-coupling reactions enable these silicon dienes to be used as synthons for a variety of other dienes one might prepare and need access to. Two of the silicon-substituted Diels−Alder cycloadducts and one of the Hiyama cross-coupling products were also characterized by X-ray crystallography.