Investigations On Several Reactions Based On Palladium-Catalyzed Allylic Alkylation

Palladiumcatalyzed allylation is very effective for the synthesis of unsaturated organic compounds.π-allylpalladium intermediates can react with various nucleophilic reagents to synthesize many allyl compounds containing C-C, C-O, C-N and C-S bonds. Among these the allyl-substituted esters and amides are essential important for their application in synthesizing some important natural products, drugs and bacteria, etc.π-allylpalladium compounds can be used as dipoles to react with unsaturated alkenes to form some heterocyclic compounds with high efficiency and selectivity. Several reactions based on π-allylpalladium intermediates were studied in this thesis, including:1."One-Pot" synthesis of allyl-substituted esters (amides). One-pot synthesis of a-phenyl-y,8-unsaturated esters or amides has been realized by the Pd-catalyzed coupling of a-aryl N-acetylbenzotriazoles with allylethylcarbonate, giving yields up to86%. The currently reported synthesis of allyl-substituted esters (amides) are mainly about direct palladium-catalyzed allylations of esters (amides). The main disadvantage of these methods is that a strong base is needed to remove the proton on the a-carbon atom of the esters (amides), thereby side reactions such as ester condensation will be caused under such strong alkaline conditions. In this thesis, a-phenyl-N-acetyl-benzotriazole was chosen as the nucleophile, which is a rarely-used "hard" nucleophile in this kind of reactions with benzotriazole (Bt) as the leaving group and can be used to avoid the disadvantage mentioned above effectively. Furthermore, the effects of catalysts, ligands and solvents on the yields were investigated; the optimum reaction conditions were determined and the possible mechanism was proposed; the products were identified by1H NMR and13C NMR. The synthetic method is effective and environment-friendly for its mild conditions, higher yields, simple experimental operation, without intermediate separation in the reaction process, less pollution and less energy consumption.2.1,3-oxazine analogues were synthesized by means of palladium-catalyzed cycloaddition of π-allylpalladium dipole in this thesis. Currently1,3-oxazine analogues were synthesized mainly by palladium-(TMM)[3+2] cycloaddition, which is limited in some aspects:(1) The substrates can only be changed with diene receptors and the restriction of substrate is apparent;(2) Strong base such as n-BuLi and low temperature are needed for the introduction of substituents containing silicon. In this thesis,2-methylene-1,3-propanediol analogues as a kind of easily-synthetic compounds were used as the substrate in the cycloaddition, which can react under relatively mild conditions and thus the reaction conditions for the synthesis of1,3-oxazine analogues would be improved effectively. However, the method we used still needs some further improvements for its present unsatisfactory yields.