Preparation And Performances Of α-Reactive Pyrylium Salts

Pyrylium salts are a type of heterocyclic compound with a positive charge character at a and y positions. Because of this property, they have played an important role as versatile synthetic intermediates for complex heterrcyclic skeletons which are utilized in many fields, such as biology, pharmaceutics, nonlinear materials, polymer science, etc. Here we investigated the reactions of a series of polysubstituted pyrylium salts withη3-phosphines which were selectively synthesized for the comparisons. The main points of this dissertation are as follows:1. As precursor compounds, a series of polysustituted pyrylium salts were synthesized, including 2-phenyl pyrylium salt,2,4-diphenyl pyrylium slat,2,4,5-triphenyl pyrylium salt, 2,4,6-triphenyl pyrylium salt,2,3,4,5-tetraphenyl pyrylium salt,2,3,4,6-tetraphenyl pyrylium salt,2,3,4,5,6-pentaphenyl pyrylium salt,2-methyl-3,4,5,6-tetraphenyl pyrylium salt, 2-ethyl-3,4,5,6-tetraphenyl pyrylium salt,2,4,6-trimethyl pyrylium salt,2-methyl-4,6-diphenyl pyrylium salt,2,3,4,5,6-pentamethyl pyrylium salt, and 2,5-dipenyl-3,4-di(p-methyl)phenyl pyrylium salt. Some processes of the synthesis have been improved effectively. The a-reactive 2,5-dipenyl-3,4-di(p-methyl)phenyl pyrylium salt was firstly reported.2. The reactions of polysubstituted pyryliums salts withη3-phosphines have been explored. The phosphonium salts formed through the reaction are fully characterized by 1H, 13C,31P NMR spectroscopy, elemental analyses, and X-ray crystallography. The results indicated that too many electron donating alkyl-substitutents did weaken the theα- and its paraβ-position of pyrylium salts played key role in the synthesic process and were important for the stability of the obtained phosphonium salts.3. Four PTPCPY (phosphonium triphenylcyclopentadienylide) ligands have been synthesized by treatment of triphenylcyclopentadienyl phosphonium salt with sodium hydroxide in excellent yields. Molybdenum complexes of three PTPCPY ligands have also been synthesized and characterized spectroscopically and crystallographically. The direct comparisons were made among these compounds. The results indicate that the steric effects of the PR3 moiety are generally as important as electronic ones and could dominate in some cases.4. The possible intramolecular Wittig reaction mechanism of 2,4,5-triphenylpyrylium salt withη3-phosphines was postulated, and a series of experiments were designed to support this mechanism. The preliminary results supported the mechanism of a tandem conjugate addition and intramolecular Wittig reaction, during which theα-reactivity of pyrylium salt has a profound effect on this ring contraction.5. The acyclic phosphonium salts converted from 2,4,5-triphenylpyrylium salts could act as the MitoTracker (mitochondrial tracker) in living cells due to their good lipophilic properties and little cytotoxicity. Furthermore, the relatively good amphiphilic properties of 2c(PMe3) show the potential that it could be used as targeted drug delivery toward mitochondria.