Electrophilic Reactions Of Functionalized Allenes And Design, Synthesis, And Application Of New Type Of Electron-rich And Sterically Bulky Monodentated Phosphine Ligands

This dissertation may be divided into the following two parts:Part1. Electrophilic reactions of functionalized allenesNowadays, allene chemistry has attracted wide attention and research because of its good reaction diversity and activity. As the continued work base on the electrophilic reactions of functionalized allenes in our group, the following two research areas have been carried out:1. Electrophilic fluorination reactions of2,3-allenoatesWe successfully synthesized (E)-3-fluoro-4-oxo-2-butenoates or4-fluoro-2-(5H)-furanones from2,3-allenoates under different conditions respectively. The mechanism was also proposed based on the isolation of key reaction intermediate.2. Electrophilic iodocyclization reactions of4,5-allenolsA series of2-[1’-iodo-1’(Z)-vinyl]tetrahydrofuran (Z/E>96/4) were afforded by the electrophilic cyclization reactions between4,5-allenols and iodine. When the substituents were introduced into3-position of allenols, the cyclization products were obtained with high diastereoselectivities (dr>96/4). Optically active (Z)-iodo-vinyltetrahydrofuran derivatives (Z/E>99/1) were synthesized via the reaction of axially chiral4,5-allenols with NIS followed by the kinetic resolution reaction applying Sonogashira couplings.Part2. Design, synthesis, and application of new type of electron-rich and sterically bulky monodentated phosphine ligandsThe bulky and electron-rich phosphine ligands were widely used in activation reactions of inert bonds. In this dissertation, three new monodentated phosphine ligands were developed for different reactions with organic chlorides:1.2,4,6-Trimethoxyphenyl dicyclohexylphosphine (LB-Phos)When using PCy3and S-Phos as the ligands in Pd-catalyzed Suzuki coupling reactions of optically active4-chloro-2(5H)-furanones, very serious racemizaton occurred. After analyzing the structure of the intermediate, we developed a new phosphine ligand-LB-Phos. With Pd/LB-Phos catalyst system, the chirality in optically active4-chloro-2(5H)-furanone was transferred into the product without racemization. This catalyst system could also be used in Suzuki coupling reactions of inert aryl and vinyl chlorides to form the products selectively.LB-Phos was also applied in Pd-catalyzed Sonogashira couplings of propagylic carbonates to form the allenyne derivatives in moderate to good yields without other metal co-catalysts.2.2,6-Diisopropoxyphenyl dicyclohexylphosphine (Gorlos-Phos)Since most of the previous reported C-Cl bond amination reactions were carried out using tBuONa or tBuOK as the base, many base sensitive functional groups could not be tolerated under these conditions. This problem was solved by using our new developed Pd/Gorlos-Phos-catalyst system which could catalyze the amination reactions of C-Cl bond using KOH as the base. The reaction mechanism was also proposed according to the31P NMR analysis research, kinetic research, and computational chemistry.3.2-Methoxy-5-(N-methyl-N-phenyl)aminophenyl dicyclohexylphosphine (Zheda-Phos)In this part, Pd/Zheda-Phos-catalyzed arylation reactions of ketones with C-Cl bonds were introduced. With this new catalyst system, not only acetyl type aromatic ketones but also acetone could form the mono-arylated products selectively with various aryl chlorides. These two processes were considered to be challenging before.