Tandem Reactions Based On The Sulfur Ylides And Photocatalytic Strategy

Heterocyclic compounds are of great significant in material, agriculture and pharmaceutically related research areas because of the natural abundance and prominent bioactivities. Organic synthesis is a powerful tool for generating novel moleculars, and its rapid development brings us much convience. However, in addition to all advantages, it also makes people have to face the problem of their impact on the environment. In this regard, the development of novel synthetic strategies and efficient and green approaches for heterocyclic synthesis is highly desirable. In this dissertation, my programs are focused on the highly efficient synthesis of heterocyclic compounds through tandem reactions of sulfur ylides and the reactions promoted by visible light irradiation.1、A formal [4+1]/[3+2] cycloaddition sequence of sulfur ylides and alkene-tethered nitroolefins has been developed. The use of (R)-binol-derived chiral sulfide leads to an asymmetric process that allows the construction of oxa-and aza-angular triquinanes in good to excellent diastereoselectivities and enantioselectivities (up to96%ee,>95:5dr). The absolute configuration of triquinane product was unambiguously confirmed to be (3aS,4S,8R,9R,9aS) by X-ray crystallographic analysis. And we have proposed a model which can rationalize the origin of stereo-discrimination in this tandem reaction.2、An addition-cyclization reaction of (1H-indole-2-yl)methanols and vinyl sulfonium salts has been developed. It provides biologically and pharmaceutically important oxazino[4,3-a]indoles in good to excellent yields (up to93%yield). This methodology can also be used in the preparation of pyrazino[1,2-a] indole derivatives. The synthetic utility of this transformation was highlighted in the synthesis of3,4-dihydro-7,8-dimethoxy-10-(4-methoxyphenyl)-1H-[1,4]oxazino[4,3-a]indole, a drug candidate for the treatment of tumors of the blood. Comparing with conventional three-step synthesis the current one-step procedure represents a significant improvement in terms of the criteria of green chemistry.3、A direct and efficient synthesis of2,3-unsubstituted1-acylpyrrolo[2,1-a]isoquinolines by1,3-dipolar cycloaddition of stabilized isoquinolinium N-ylides with vinyl sulfonium salts (up to88%yield) has been developed. This process features simple experimental procedures, under mild conditions.4、A visible light-induced, aerobic oxyamidation reaction of indoles, using oxygen in air as the oxidant, has been developed. This process serves as a photocatalytic strategy to generate efficiently tetrahydro-5H-indolo[2,3-b]quinolinols, which owing to their privileged indoline structure, may have interesting biological and pharmacological activities (up to79%yield,>95:5dr). In addition, based on18O-labeling experiments and electrochemical analysis, we proposed a novel mechanism for this reaction.