| Semipinacol rearrangement reaction is a powerful tool for constructing complicated molecular skeletons in organic synthesis.The generation of electrophilic carbon center is the key for this transformation.Among the strategies to produce this transient species,visible-light photoredox catalysis has attracted increasing research interest from synthetic community due to its extremely mild condition and the diversity of semipinacol rearrangement reaction.In the field of visible light photo-catalysis,N-acyloxyphthalimides and cyclobutanone oxime esters have been well established as two kinds of alkyl radical precursors.In this thesis,two photo-catalytic tandem alkyl radical addition/semipinacol rearrangement reactions of cycloalkanol-substituted styrenes with N-acyloxyphthalimides and O-acyl oximes have been documented.First,we investigated this reaction with 1-[1-(4-methoxyphenyl)vinyl]cyclobutan-1-ol and 1,3-dioxoisoindolin-2-yl cyclohexanecarboxylate as the model substrates to try this reaction.After screening a series of conditions(such as photocatalyst?solvent?additive),we determined the optimal conditions for the reaction:fac-Ir(ppy)3 as a photocatalyst,N,N-dimethylaniline(DMA)as a solvent under the irradiation of 6 W white LEDs at room temperature,we can get the best results.And a series of cyclopentanone compounds were finally obtained in 33-75%isolated yield.Moreover,we have also extended this strategy to evaluate the substrate scope of the reaction between O-acyl oximes and cycloalkanol-substituted styrenes,and cyclopentanone compounds were finally obtained in 54%-92%isolated yield.All the desired products were characterized by 1H NMR,13C NMR,HRMS,IR,and the spectroscopic properties of the target compounds were studied and their spectral data were assigned.And one of them was unambiguously determined by X-ray diffraction analysis.Finally,a possible reaction mechanism was proposed according to a preliminary exploration of the reaction mechanism and literature report. |
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