The synthesis of a series of A2B‐corroles with 4‐carboxyphenyl substituent is described. The macrocycles are prepared from dipyrromethanes and 4‐formylbenzoic acid under Gryko conditions. Redox active biometal complexes are formed from the corrole carboxylic acids with the metal ions of cobalt, iron, and manganese, but not with copper. From all free corrole bases and metal complexes, the respective active esters are obtained in good yields by condensation with NHS (N‐hydroxysuccinimide) and EDC (1‐ethyl‐3‐dimethylaminopropyl‐carbodiimide). Starting from the active esters of the free corrole bases, the copper corroles are accessible in acceptable yields. Oxidation‐ and spin states of the biometal corroles correspond to those of simple corroles and are confirmed spectroscopically and magnetically. Ethylenediamine is efficiently coupled with the corrole carboxylic acids by EDC, whereby selective two‐fold coupling is observed. For the coupling to NαBoc‐lysine as well as NαFmoc‐lysine the use of corrole active esters is advantageous. The metalation of corroles carrying N‐protected lysine side chains turns out to proceed only with loss of most of the material. Here, the coupling of the amino acid building block with the metal corrole active ester proved to be the synthetically more applicable variant. The resulting NαFmoc‐lysine conjugates of both a free base corrole and a manganese corrole complex are shown to be suitable for use in Merrifield solid phase peptide synthesis.
The formation of meso‐aryl‐BODIPYs (boron dipyrrins) through the acidic condensation of 3,4‐dialkylpyrroles with aromatic aldehydes, followed by 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) oxidation and BF2 complexation, has been reviewed. Surprisingly, it was found that the major products from these reactions were not the anticipated symmetric BODIPYs, but non‐symmetric derivatives carrying one benzyl substituent at the BODIPY α position. The best yields and simple purification conditions were be achieved if the oxidant was not employed in the one‐pot reaction sequence. Electron‐rich benzaldehydes provided the best results, whereas precursors with electron‐withdrawing substituents gave significant amounts of the symmetric BODIPYs as side‐products. This unexpected result can be rationalized mechanistically on the basis of two reaction pathways that diverge from a common intermediate at an early step in the condensation sequence. Preliminary reactivity investigations showed chlorination to give unexpected results, but a typical substitution and coupling chemistry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.