Studies on synthesis of novel porphycene analogs and Eu(fod){209}-catalyzed rearrangement of allylic esters

Porphycene is among the most stable porphyrin analog known today. Numerous synthetic strategies were developed for synthesizing the dialdehydes or diketones over last decade for making varies porphycene analogs. The first part of the thesis focuses on synthesis of dialdehydes and diketones by using the Suzuki cross-coupling, which were then used for making novel porphycene analogs. The second part emphasizes on the Eu(fod)3-catalyzed regiospecific rearrangement of allylic esters which can be applied for 1,3-diene synthesis. Furthermore, the tandem reaction combining the allylic ester rearrangement and Diels-Alder reaction by using Eu(fod)3 as the catalyst has been established as well. The thesis begins with a brief introduction of porphycene (a porphyrin derivative) where the previous approaches to various porphycene analogs are presented. In chapter 2, selected methodologies towards dialdehydes and diketones are reviewed followed by a background description on dialdehyde synthesis by using the Suzuki cross-coupling. Dioxadithiaporphycenes as well as the first benzene-incorporated porphycene analog have been synthesized in this study. As an extension of chapter 2, we attempted to fuse two benzene rings into the porphycene skeleton in chapter 3. The research started with the McMurry coupling of monoalkynyl ketones. However, attempt to couple the dialkynyl ketones was unsuccessful. Besides, the Sonogashira cross-coupling also failed to connect such large ring system mainly due to loss of entropy and huge ring strain. In chapter 4, the Eu(fod)3-catalyzed rearrangement of allylic esters was studied. The reactivity of a series of p-methoxybenzyloxyacetates towards Eu(fod)3-catalyzed allylic rearrangement was examined. Generally, the reactivity toward rearrangement is influenced by the substituents. Studies on allylic alkoxyacetates revealed that the migrating ability of the esters follows the trend of p-(trifluoromethyl)benzyloxyacetate > methoxyacetate > benzyloxyacetate > p-methoxybenzyloxyacetate. It is explained by the electron-withdrawing power of the alkoxy group. The final chapter outlines a novel strategy for 1,3-diene synthesis as well as the tandem reaction combining the allylic ester rearrangement and Diels-Alder reaction. The unsymmetrical divinyl alkoxyacetates underwent a Eu(fod)3-catalyzed regiospecific allylic rearrangement to form the C5-substituted (E)-2-ethoxy-1,3-dienes at room temperature. Then, a tandem strategy was carried out by rearrangement the allylic esters in the presence of dienophiles (TCNE, MA, BQ, DMAD) and Eu(fod)3. Compared with the stepwise process, the overall yield of the final product was greatly improved in the tandem process. Because 1,3-dienes are versatile starting materials, the tandem strategy developed in this thesis work should find applications in contemporary organic synthesis as well