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 ‘3+1’ condensation with tripyrrane 3 will the afford phenaliporphyrin.

Investigations directed towards the synthesis of phenaliporphyrin

2019 Spring National Meeting

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