RUI: Carbaporphyrins, Carbachlorins and Related Conjugated Macrocycles

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With this award, the Chemical Synthesis program is supporting Professor Timothy Lash at Illinois State University to explore the synthesis, characterization, and reactivity of porphyrin-like macrocycles. Porphyrins are large-ring heterocycles which possess many valuable properties and have applications in materials science, catalysis and medicine. Porphyrins are widely distributed in nature as catalytic sites in enzymes. Far less research has been reported on porphyrin-like macrocycles or porphyrinoids even though these systems demonstrate properties that complement those of true porphyrins. This research will lead to more efficient routes to carbaporphyrinoid systems, in which one nitrogen is replaced by carbon, and will also provide access to new classes of porphyrin analogues. These projects will improve our understanding of fundamental chemistry concepts such as aromaticity. The new porphyrinoids may find applications in the preparation of fine chemicals, since metalated derivatives can be used to construct catalysts for chemical synthesis. Broader impacts of this research lie in applications of these new substances and in student training. The target compounds have potential medicinal applications as photosensitizers in photodynamic therapy. These projects provide an excellent environment for training undergraduates and M.S.-level graduate students in the field of organic synthesis. Students will be exposed to the multidisciplinary nature of modern scientific research.In this research, synthetic routes to novel carbaporphyrins and related porphyrinoids, including "neo-confused" porphyrins, carbachlorins and dicarbaporphyrinoids, will be developed. Further application of the [3 + 1]-variant on the MacDonald reaction will allow the synthesis of porphyrinoids with pyranone, phenalene, pyrene and benz[f]indene units, and these studies will be extended to the preparation of fused carbaporphyrinoid dimers. A new synthetic approach to carbaporphyrinoids will also be developed using carbatripyrrin intermediates. This strategy will allow more direct access to carbaporphyrins, heterocarbaporphyrins and dicarbaporphyrins starting from indene or cyclopentadiene. Carbachlorins have been little studied to date, and new routes to dihydroporphyrinoids will also be developed. Carbachlorins have useful properties in their own right and may also act as precursors to carbaporphyrins. Furthermore, syntheses of adj-dicarbaporphyrins will be investigated using a base catalyzed MacDonald [2 + 2]-approach and attempts will be made to prepare tri- and tetracarbaporphyrinoid systems. The properties of this new collection of macrocycles will be investigated.