Core-Modified Smaragdyrins:  First Examples of Stable Meso-Substituted Expanded Corrole

Abstract

A synthetic access to the first members of expanded corroles 1 and 2 is achieved through formation of two direct pyrrole−pyrrole links by an oxidative coupling reaction. Spectroscopic and structural analysis reveal that 1 and 2 are 22Π aromatic macrocycles despite the nonplanar structure and properties resemble that of isocorroles rather than 22Π sapphyrins. Sapphyrin 1 is an example of the simplest possible expanded porphyrin with 22Π electrons. 1 The existence of sapphyrins was been reported long ago, but their rich and diverse chemistry has been explored only recently after the development of efficient synthetic methodologies allowing their preparation in gram quantities. Removal of one meso carbon from the sapphyrin skeleton results in a new 22Π electron macrocycle with two direct pyrrole-pyrrole links. This structural principle is referred to as "smaragdyrin" 2 in the literature. 2,3 The structural relationship between 1 and 2 is analogous to that between a porphyrin and a corrole; therefore, the chemistry of smaragdyrins is expected to resemble that of corroles. 4 Two previous attempts to syn-(1) For the recent reviews and papers on the expanded porphyrins, see: (a) Jasat, A.; Dolphin, D.

Synthetic Expanded Porphyrin Chemistry

“…[61] For example, an oxidative coupling between the heterotripyrranes 43 and the dipyrromethane 42 gives rise to heterosmaragdyrins (Scheme 6). In the case of the oxasmaragdyrin 44 b (Ar = Ph), the reported yields are as high as 51 %, while for the corresponding thiasmaragdyrins, the yields are significantly lower, namely, 5 % for 44 a (Ar = Ph).…”

“…Catalytic decomposition of peroxynitrite by a manganesetexaphyrin complex. [61] Expanded Porphyrins Angewandte Chemie Figure 15. In the same report, the possibility of using the protonated form of 44 b as an anion receptor was also noted (see Figure 16 for the X-ray structure).…”

5,10,15-Triaryl-21,23-dioxacorrole and Its Isomer with a Protruding Furan Ring

“…Recently, Chandrashekar and co-workers have demonstrated that the R-R coupling of 5,10-diphenyl-16-oxatripyrrane and dipyrromethane yields 5,10,15-triaryl-21-oxacorrole. 32, 33 Lindsey and co-workers have remarked that the condensation of 5-(p-tolyl)-dipyrromethane and furylpyrromethanediol yielded 5,10,15-triaryloxacorrole in addition to the expected 5,10,15,20-tetraaryl-21-oxaporphyrin. 34 Lee and co-workers have reported on an original way to produce 5,10,15-triaryl-21-oxacorrole and, for the first time, the isomeric 5,10,15-triaryl-22-oxacorrole. 35 Finally, the Vogel group succeeded 36,37 in preparation of tetraoxacorrole cation and octaethyltetroxacorrole cation, although these results are practically available in the review articles.…”

Recent Advances in the Synthesis of Corroles and Core-Modified Corroles

“…Chandrashekar and co-workers found that the acid-catalyzed coupling of dipyrromethane 23 and 16-oxatripyrrane 24 catalyzed by BF 3 ·OEt 2 leads, in addition to the expected core-modified smaragdyrin (26), also to core-modified corrole 25 as a side product (Scheme 12). [51] The formation of core-modified corroles in this [3ϩ2] reaction is due to the fact that both substrates are susceptible to acid-catalyzed rearrangements and are known to undergo fragmentation.…”

“…[52] Complexes of oxacorroles with Cu II , Ni, II or Co II have already been prepared by reaction with CuCl 2 , NiCl 2 , or Co-(OAc) 2 in DMF. [51] The chemistry of triazatetrabenzocorroles, first obtained by Fujiki et al, [53] was recently further developed by Hanack and co-workers. They found that reaction of diiminoisoindoline 31 with Si 2 Cl 6 leads to the ring-contracted (hydroxy)(α,β,γ-triazatetrabenzocorrole)silicon 32 (Scheme 14).…”