Studies On Palladium Catalyzed Carbonylation Reactions Of Multifunctional Unsaturated Compounds

As an important method for the introduction of a carbonyl moiety into an organic molecule, transition metal complex-catalyzed carbonylation reactions have received great deal of attention in recent years. The development of transition metal-catalyzed carbonylation reactions include involving employing the " catalyst killer" chalcogen compounds as a substrate and the application of advanced techniques such as microwave irradiation. Our efforts in this challenging and interesting area are well described in this thesis. The whole dissertation consists of two parts:Part 1 describes the studies on the cyclizaition and carbonylation reactions of (Z)-enynols with thiols or other nucleaphilic reagents and carbon monoxide. Initial catalyst screening indicated that the use of different palladium(0) or palladium (â…¡) complexes with added phosphine ligands displayed different catalytic activities with respect to the formation of the two kinds of lactones. The use of Pd(OAc)₂/PPh₃ or Pd(PPh₃)₄ gave the highest selectivity for the dicarbonylation lactone. The reaction with the use of bidentate phosphines such as dppp and dppb gave the lower selectivity, affording the mixture of the di-and mono-carbonylation products. The cyclodicarbonylation reactions of a series of enynols with other thiols were performed at the optimized conditions. All thiols and thiolphenols afford good results except the one bearing strong electron-withdrawing groups. Enynols with terminal alkyne moiety show good reactivities under these conditions, while enynols with internal triple bond are unreactive. A possible mechanism of this double carbonylation reaction was proposed here. We also checked the reactions between enynols and other nucleophilic regeants. The results show that, Pd(0)-complex catalyzed carbonylation reaction between enynols and alcohols occurs proceeds in the similar way as the reaction between enynols and thiol does, while amine and carbon nucleophilic regeants do not show any reactivity.Part 2 presents the studies on the microwave-accelerated palladium-catalyzed carbonylative cyclization reactions of 2-iodophenol with alkynes. Rapid palladium-catalyzed carbonylation reactions of 2-iodophenol with various alkynes have been carried out by the use of commercially available molybdenum hexacarbonyl as a convenient and solid carbon monoxide source. The reaction affords the corresponding chromen-2-one derivatives in good to excellent yields in 30 mins while under traditional condition the reaction time is longer than 18 hours. Internal and terminal alkynes can be successfully employed in the reaction. The regioselectivity of this reaction depends on the substrate employed. The terminal alkynes reacted with 2-iodophenol to afford exclusively the chromen-2-one derivatives in pretty good yields. Mixtures of chromen-2-one and chromen-4-onewere obtained with modest regioselectivity when internal alkynes were applied in the reaction. The possible mechanisms were also discussed to explain the selectivity.