Investigations into the Synthesis of Phenaliporphyrins

Benziporphyrins 1 are nonaromatic porphyrinoids with a cross-conjugated 6π electron arene subunit. However, modification of this system can result in the formation of aromatic macrocycles. In this project, a benziporphyrin-like system 2 incorporating a phenalene subunit has been targeted for investigation. It is anticipated that this porphyrinoid will take on fully aromatic characteristics while retaining a fused naphthalene moiety. The required precursors to 2 are tripyrranes such as 3a and 3b, and tricyclic dialdehydes 4 or 5. Initial attempts to prepare 4 by performing a Wittig condensation with perinaphthenone, followed by a Vilsmeier formylation, were unsuccessful. Currently, an alternative synthetic route to 5 is being developed beginning with 1-tetralone. Naphthylsuccinic anhydride 6 has been prepared and cyclized to produce keto acid 7a. It is anticipated that esterification to produce 7b, followed by a Wittig condensation and reduction with DIBAL-H, will afford the required dialdehyde 5. Subsequent ‘3+1’ condensation with tripyrranes 3 will the afford phenaliporphyrins 2.https://ir.library.illinoisstate.edu/ursche/1000/thumbnail.jp

INVESTIGATION DIRECTED TOWARDS THE SYNTHESIS OF PHENALIPORPHYRIN

Carbaporphyrins and related systems are porphyrin analogues where at least one of the inner nitrogens have been replaced with carbons. These macrocycles may have global aromaticity but in some cases the structures are nonaromatic or even antiaromatic. Benziporphyrins 1 are nonaromatic porphyrinoids due to the 6π electron arene unit introducing cross-conjugation. In this work, a benziporphyrin-like system 2 incorporating a phenalene subunit has been targeted for investigation. It is anticipated that this porphyrinoid will take on fully aromatic characteristics while retaining a fused naphthalene moiety. The required precursors to 2 are tripyrrane 3 and dialdehydes 4 or 5. Initial attempts to prepare 4 by reacting perinaphthenone with (methoxymethyl)triphenylphosphonium chloride in a Wittig condensation, and then carrying out a Vilsmeier formylation, were unsuccessful. Currently, an alternative synthetic route to 5 is being developed starting with 1-tetralone. It is anticipated that cyclization of naphthalene intermediate 6 will afford a keto acid that can be converted into 5. Subsequent \u273+1\u27 condensation with tripyrrane 3 will the afford phenaliporphyrin

Synthesis of Highly Conjugated Porphyrinoid Systems

Porphyrins are a group of naturally occurring heterocyclic macrocycles comprising of four pyrrole subunits connected by four methine bridges. Metalloporphyrins, such as heme and chlorophyll, serve as cofactors in essential biological processes, making them one of nature’s most versatile ligands. However, porphyrinoid structures are not only of biological relevance, but they show intriguing spectroscopic properties which are commonly attributed to their [18]annulene-like delocalization pathway. Porphyrinoid systems are widely studied via modifications such as the introduction of additional conjugated units, particularly fused aromatic rings. The synthesis and subsequent modification of chrysoporphyrin and anthro[2,3-b]carbaporphyrin demonstrates that fusion of aromatic rings onto the porphyrinoid system has a measurable impact on the electronic structure and it induces bathochromic shifts of key signals in the UV-vis spectra as well as altering the strength of the diamagnetic ring current