Direct β-Acyloxylation Of Enamines Via PhIO-Mediated Intermolecular Oxidative C-O Bond Formation And Its Application To The Synthesis Of Oxazoles

1,3-Oxazole, also known simply as oxazole, are important compounds and haveattracted great interest due to their appearance as subunit of various biologicallyactive natural products as well as their utilities as valuable precursors in many usefulsynthetic transformations. A large number of oxazole-containing natural productshave been isolated from marine invertebrates and microorganisms. The synthesis ofnatural products with the common biogenic oxazole moiety has attracted the attentionof several chemists for decades.Recently, iodine(III) reagents are boosting the preparation of variousheteracycles for their unique oxidative properties in C-C, C-O and C-N bondformation. One of the most useful aspect of these oxidant, includes PIDA and PIFA, isthe reaction with β-monosubstituted emaines. This thesis mainly introduces theresearch of the systhesis of β-acyloxy enamines and oxazoless including the followingaspects:1. Based on the literature review and research results from our group, anapproach to synthesize β-acyloxy enamines and oxazoless by the oxidation ofβ-monosubstituted enamines via hypervalent iodine reagent was developed.2. Under the oxidation of PhIO, β-monosubstituted enamines and carboxylicacids (including N-Boc-amino acids) can be coupled at ambicient temperature.Therefore, according to the influence of electronic effect and steric effect, wedesigned various β-monosubstituted enamines and carboxylic acids as substrates tocompose21distinct β-acyloxy enamines for measuring the impacts of sundtituentgroups on the reaction yield and velocity.3. The procedures for preparing oxaoles from β-acyloxy enaminesandβ-monosubstituted enamines were established. And17oxalozes were synthesizedby these methods.4. The application of this methodology was preliminarily explored bysynthesizing3oxazoles containing chiral amino-acid residues and the stabilities oftheir chiral centers under such condition was studied by NMR and chiral separation.5. The mechanism of this recation was supposed by literature review and logicl analysis. Moreover, the control test was conducted to prove it.Advantages of the method include the readily availability of the startingmaterials, the mild reaction condition and the much desired transition-metal-freefeature. Moreover, the transformation can tolerate a wide range of functional groupsand furnish a variety of β-acyloxy enamines that can be further cyclized to oxazolecompounds.