| The applications of Pd- and Ru-catalyzed reactions have profound impact on organic synthesis by achieving atom economical transformations that may not be feasible by conventional methods.; The development of a Ru-catalyzed [5+2] cycloaddition of vinylcyclopropane alkynes leads to the synthesis of seven-membered ring compounds. The scope, mechanism, diastereoselectivity and regioselectivity have been extensively investigated. The reaction was used for the highly diastereoselective construction of tricyclic compounds containing a seven-membered ring, which demonstrates the potential of this strategy to be applied to the total synthesis of complex natural products. This cycloaddition was also employed in synthetic efforts towards dehydroleucodin.; The Pd-catalyzed intramolecular asymmetric allylic alkylations (AAA) of phenol allylic carbonates provide a facile access to chiral chromans. The unusual acetic acid effect, the influence of olefin geometry and substitution pattern on the ee, and the absolute configuration of the chiral chromans suggest a mechanism involving the cyclization of the more reactive Pd-π-allyl diastereomeric intermediate as the enantiodiscriminating step (Curtin-Hammet conditions). This methodology led to the first enantioselective total synthesis of (+)-clusifoliol, the first enantioselective biomimetic total synthesis of (−)-siccanin, and the enantioselective synthesis of an advanced intermediate towards the total synthesis of rhododaurichromanic acid A.; In ancillary studies, the Pd-catalyzed diyne cycloisomerizations afforded 1,3-dienes, which was employed in synthetic efforts towards (+)-streptazolin. The Ru-catalyzed Alder-ene reactions of internal alkynes and alkenes offered a stereoselective synthesis of trisubstituted alkenes. |
