Studies On Selective Catalytic Oxidation/Oxygenation Reactions Of Carbonyl Compounds

Transformations that generate different molecular architectures from same or similar starting materials by selective catalysis provide an expedient approach to molecular diversity synthesis. In this thesis, the new developments on selective synthetic reactions (involving selective catalysis reactions catalyzed by transition metal or organocatalysts) in recent years are initially summarized. On this basis, three types of selective catalytic oxidation/oxygenation reactions of carbonyl compounds are presented. The details are summarized as following:1. We have developed an N-heterocyclic carbene (NHC)-catalyzed0-selective addition of nitrosoarenes with aldehydes, giving rise to O-acyl hydroxylamines without any detectable competing amidation by-products. High regioselectivity and moderate to good yields were observed for a wide range of substrates. The results revealed that a dual activated transition state underwent in the reaction. Key to the success of this reaction is the right choice of the NHC precursor and base. In addition, we developed an one-pot tandem reaction catalyzed by NHC involving aldehydes, nitroso compounds and allenyl ester, NHC-catalyzed direct amidation of nitroso compounds and aza-Cope rearrangement proceeded stepwise.2. We have develped a flexible protocol for the selective synthesis of chiral dihydropyranones and2H-pyran-2-ones from the same starting materials of β-bromoenals and1,3-dicarbonyl compounds upon controlled and divergent NHC catalyzed oxidative transformations. The elimination of the bromo atom could be controlled by changing the reaction conditions (adding external oxidant or not), allowing the Breslow-type intermediate generated from NHC and β-bromoenals transformed to two sorts of unsaturated acyl azoliums, leading to different types of heterocyclic compound, respectively. The method further expands the application of β-haloenals catalyzed by NHC.3. We have developed a novel catalytic aerobic ring-transformation reaction of 2H-pyran-2-ones under visible light, upon choosing appropriate solvents, functionalized5-hydroxylfuran-2-(5H)-ones and furan-2-(5H)-ones with potential biological and synthetic utility could be synthesized efficiently under very mild conditions. Some18O labeling experiments revealed that dioxine derivatives may be generated as the intermediate, which underwent subsequent oxidation or rearrangment to form the targeted products. The current protocol method expands the synthetic application of visible light photocatalysis and provides an alternative route to furan-2-(5H)-ones derivatives.