| Initially, the reactivity of a variety of 1,2-dihaloethylene compounds (olefin templates) towards palladium catalyzed cross-coupling reactions was investigated. Suzuki, Sonogashira and Negishi reactions were conducted on E-1-chloro-2 iodoethylene, E-1-bromo-2-iodoethylene, E-1,2-diiodoethylene and E- and Z-1,2-dibromoethylene. Only E-1-chloro-2-iodoethylene provided the desired coupling products reliably under all reaction conditions. E-1,2-Diiodoethylene did not provide mono-coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates E-1-bromo-2-iodoethylene and E- and Z-1,2-dibromoethylene. Studies indicated that oxidative addition of the most reactive carbon-halogen bond to palladium (0) was followed by elimination of the second halide, when the second halide was a bromide or an iodide.;The next two projects led to the total syntheses of three polyene-containing natural products, taking advantage of an olefin template strategy. The naturally occurring ant venom (13E,15E,18 Z,20Z)-1-hydroxy-4-oxopentacosa-13,15,18,20-tetraen-11-yn-1-ylethanoate was synthesized stereospecifically using a series of palladium mediated cross-coupling reactions. The use of the difunctionalized olefin template E-1-chloro-2-iodoethylene as the central, pseudosymmetrical building block facilitated a fully convergent and, thus, efficient strategy to prepare this polyunsaturated natural product. The ultimate utility of an olefin template strategy was conveyed by applying E-1-bromo-2-iodoethylene as a building block for the convergent and modular synthesis of two related natural products, E- and Z-Bupleurynol. In doing so, a 9-step synthesis of Z-Bupleurynol was reduced to one single operation by using queued cross-coupling reactions with palladium catalysts, negating the need for any protecting group chemistry.;In the last part of the thesis a variety of tetrafunctionalized olefin templates were prepared and their utility towards the stereospecific synthesis of tetrasubstituted olefin was investigated. |
