Organocatalyzed enantioslective synthesis of 2-aminoo-4H-chromenes and oxindole derivatives
Performing asymmetric transformations is one of the most interesting and challenging areas of organic chemistry. It is known that in many cases only one of the two enantiomers exhibit the desired biological activities and, therefore, to develop an enantioselective synthesis of the desired enantiomer in an asymmetric transformation is desirable in medicinal chemistry as well as in the pharmaceutical industry. Using organocatalysts to perform asymmetric transformations is one of the emerging areas of the modern organic chemistry. They are related to biocatalysts (such as enzymes), but are much easier to access chemically and have usually much broader substrate scope. Among the reported organocatalysts, bifunctional organocatalysts are capable of activating both the electrophile and the nucleophile simultaneously and frequently demonstrate superior reactivity and stereoselectivity. We hypothesized that this mode of activation is also applicable to substrates and reagents that are not normally considered in traditional organic chemistry but are very important for the synthesis of biologically active molecules. This dissertation will demonstrate the applications of Brönsted base bifunctional catalysts in synthesizing enantiomerically enriched biologically active molecules through novel tandem Michael addition sequences. This dissertation work also provides a novel base-catalyzed reaction pathway to synthesize Baylis-Hillman adducts which are known to exhibit great synthetic utility in modern organic chemistry.