Studies On New Cross-couping Reactions Based On Palladium-catalyzed C-S Bond Activation Of Ketene Dithioacetals

In the area of transition metal-catalyzed cross-coupling reactions, the C-S bondcleaving reaction have attracted a lot of attention in the last decade as they provide agood alternative to the use of organo-halide reagents in traditional cross-couplingreactions. As compared to the corresponding halides, thioorganic derivative aretantalizing alternatives due to their diversity and stability. The availability of a widerange of organosulfur species provides the opportunity for developing inexpensivesubstrates and novel transformations for the synthesis of interesting organiccompounds.Easily prepared multiple functional ketene dithioacetals serves as buildingblocks for the construction of polysubstituted carbo-and heterocyclic compounds.From the point of structure, ?-oxo ketene-(S,S)acetals can be seemed as eitherfunctional thioether, or vinylogous ester. Owing to these chemical properties, wecreatively developed ketene dithioacetals to as novel electrophilic organosulfurcoupling partners, studied transition metal catalyzed C-C bond formations through theC-S bond cleavages. This thesis mainly includes five aspects:1. Palladium-catalyzed, copper-mediated desulfitative crossing-couplingbetween ketene dithioacetals and boronic acids have been studied. A convenientsynthesis of tetrasubstituted olefins under neutral conditions have been realized.2. Palladium-catalyzed, copper-mediated C S activation for [3+3] annulationof2(methylthio)benzofuran-3-carboxylates and2hydroxyphenylboronic acids havebeen realized. This method allows new approach to a class of coumestan derivatives,which possess potential biological properties and estrogenic activity.3. Copper-catalyzed C C coupling reaction of ?,?-dioxo ketene-(S,S)acetals andboronic acids to provide tetrasubstituted olefins have been realized. Actually, this isthe first example of Cu-catalyzed coupling of ordinary ester with boronic acids, andexpands the spectrum of desulfitative crossing-coupling.4. Catalyzed by Pd(OAc)2, a wide range of ?-carbamoyl ketene dithioacetalsreadily react with arynes afford functionalized2-quinolinones to selectively in highyields under neutral reaction conditions by a C-S activation/aryneinsertion/intramolecular coupling sequence. The insertion of an aryne into a C-S bondcan suppress the addition of an S nucleophile to the aryne in the presence ofpalladium. This process represents the first example for the reaction of arynes with thioorganics based on palladium-catalyzed C-S bond activation. A novel and efficientprotocol for the synthesis of functionalized2-quinolinone has been achieved.