New applications of cyclobutadiene cycloadditions: Diversity and target oriented synthesis

Cyclobutadiene cycloadditions provide rapid access to rigid polycyclic systems with high strain energy and unusual molecular geometries. Further functionalization of these systems allows entry into unexplored chemical space. A tricarbonylcyclobutadiene iron complex on solid support enables exploration of these cycloadditions in a parallel format amenable to diversity oriented synthesis. Modeling of the cycloaddition transition states with density functional calculations provides a theoretical basis for analysis of the regioselectivity observed in generation of these substituted bicyclo[2.2.0]hexene derivatives.;The high strain energy accessible in cyclobutadiene cycloadducts and their derivatives renders them useful synthons for access to medium-ring natural products through ring expansion. Torilin, a guaiane sesquiterpene isolated from extracts of the fruits of Torilis japonica, exhibits a range of biological activities including testosterone 5alpha-reductase inhibition, hKv1.5 channel blocking, hepatoprotective, anti-inflammatory and anti-cancer effects. These activities are reviewed and analyzed from the perspective of a common biochemical target.;Tandem oxidation and acid-catalyzed rearrangement of a highly strained tetracyclo[5.3.0.01,5.02,4]decane in the presence of tetrapropylammonium perruthenate provides the bicyclo[5.3.0]decane core of this natural product with complete control of relevant stereochemistry. The complex precursor required for this rearrangement is rapidly accessed by cyclopropanation of an intramolecular cyclobutadiene cycloadduct. Synthetic studies are reported which provide preliminary access to 8-deoxytorilolone.