Regioselective oxidations of benzocarbaporphyrins with ferric chloride: a facile synthesis of bridged [18]annulene ketals with strong absorptions in the far red and an unexpected halogenation reaction at the interior carbon atom.

Benzocarbaporphyrins 4 were found to undergo regioselective oxidations with ferric chloride in methanol, ethanol, isopropyl alcohol, or ethylene glycol to give bridged benzo[18]annulene ketal derivatives 5 in excellent yields. These polar derivatives were generally isolated in a monoprotonated form and the corresponding free bases appeared to be relatively unstable. Addition of TFA resulted in the formation of spectroscopically distinct dications.

Silver(III) carbaporphyrins: the first organometallic complexes of true carbaporphyrins.

Reaction of carbaporphyrins 1 with silver(I) acetate in methanol-CH(2)Cl(2) gave excellent yields of the related silver(III) complexes 6. These nonpolar organometallic compounds retain fully aromatic properties as judged by UV-vis and NMR spectroscopy and were further characterized by X-ray crystallography and cyclic voltammetry.

Conjugated macrocycles related to the porphyrins. 21. Synthesis, spectroscopy, electrochemistry, and structural characterization of carbaporphyrins.

The "3 + 1" variant of the MacDonald condensation has been shown to be an excellent methodology for synthesizing carbaporphyrins. In particular, 1,3-indenedicarbaldehyde condenses with tripyrranes in the presence of TFA to give, following oxidation with DDQ, a series of benzocarbaporphyrins in excellent yields. Triformylcyclopentadienes also afford carbaporphyrin products, albeit in low yields ranging from 5 to 8%.