Creation from Confusion and Fusion in the Porphyrin World─The Last Three Decades of N-Confused Porphyrinoid Chemistry

Abstract

Confusion is a novel concept of isomerism in porphyrin chemistry, delivering a steady stream of new chemistry since the discovery of N-confused porphyrin, a porphyrin mutant, in 1994. These days, the number of confused porphyrinoids is increasing, and confusion and associated fusion are found in various fields such as supramolecular chemistry, materials chemistry, biological chemistry, and catalysts. In this review, the birth and growth of confused porphyrinoids in the last three decades are described.

21-Carba-23-oxaporphyrinoids and 21-oxo-21-carba-23-oxaporphyrinoids: macrocyclic π-conjugation involving the carbonyl moiety

“…6 A perfect match between a metal cation radius and a crevice diameter, so significant for the coordination chemistry of porphyrins, remains conserved in 21-carbaporphyrin, providing the crucial incentive to explore unique macrocyclic organometallic chemistry. [15][16][17][18]21,22 Thus direct insertions of metal ions to 21-carbaporphyrin and 21-carba-23-heteroporphyrin have been reported. 6,8,19 Previously, inspired by the gradual emerging chemistry of 21-carbaporphyrins, we have focused our synthetic effort on the synthesis of 21-carba-23-thiaporphyrin 5 and 21-carba-23thiachlorin 6.…”

Biodegradation of 2,5-Dihydroxypyridine by 2,5-Dihydroxypyridine Dioxygenase and Its Mutants: Insights into O–O Bond Activation and Flexible Reaction Mechanisms from QM/MM Simulations

“…The pyridine ring is a dominant constituent of heterocyclic aromatic compounds, widely existing in natural plant alkaloids, coenzymes, and pyridine derivatives. − The hydrophilic pyridine-based chemicals can be easily released into the groundwater, causing pollution to the natural environment. , 2,5-dihydroxypyridine (DHP) is one of the key intermediates in the microbial transformation of nicotine and nicotinic acid (see Scheme ), . ,− which can be a potential carcinogen and cause DNA stand scission. , As nicotine dependence can cause a high risk of lung cancer for lifelong smokers, − an effective degradation of nicotine is highly required. Biodegradation of nicotine and its derivatives has attracted considerable attentions, − and particularly, the enzymatic degradation provides one of the most effective ways for the ring cleavage of aromatic compounds. − , As shown in Scheme , the 2,5-dihydroxypyridine dioxygenase (NicX) from Pseudomonas putida KT2440 can catalyze the conversion of DHP into N -formylmaleamic acid (NFM). − …”

Organometallic Chemistry within the Structured Environment Provided by the Macrocyclic Cores of Carbaporphyrins and Related Systems

“…In these systems, the metal cation is constrained within a highly ordered coordination sphere, and this can lead to unusual reactivity, including selective oxidation reactions. The best known porphyrinoids of this type are the so-called N-confused porphyrins (NCP, 1 ) [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], and these can easily be prepared by a one-pot procedure from pyrrole and benzaldehyde [ 13 , 14 ]. However, many other intriguing carbaporphyrinoid systems such as carbaporphyrins 2 and 3 [ 15 ], azuliporphyrins 4 [ 16 ], benziporphyrins 5 [ 17 , 18 ], oxybenziporphyrins 6 [ 19 ], and tropiporphyrins 7 [ 20 ] have been reported ( Figure 1 ) and these exhibit diverse structural and spectroscopic properties, unusual reactivity, and varying degrees of aromatic, nonaromatic and antiaromatic characteristics.…”