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

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.

Nucleophilic Aromatic Substitution (SNAr) and Related Reactions of Porphyrinoids: Mechanistic and Regiochemical Aspects

The nucleophilic substitution of aromatic moieties (SNAr) has been known for over 150 years and found wide use for the functionalization of (hetero)aromatic systems. Currently, several "types" of SNAr reactions have been established and notably the area of porphyrinoid macrocycles has seen many uses thereof. Herein, we detail the SNAr reactions of seven types of porphyrinoids with differing number and type of pyrrole units: subporphyrins, norcorroles, corroles, porphyrins, azuliporphyrins, N-confused porphyrins, and phthalocyanines. For each we analyze the substitution dependent upon: a) the type of nucleophile and b) the site of substitution (α, β, or meso). Along with this we evaluate this route as a synthetic strategy for the generation of unsymmetrical porphyrinoids. Distinct trends can be identified for each type of porphyrinoid discussed, regardless of nucleophile. The use of nucleophilic substitution on porphyrinoids is found to often be a cost-effective procedure with the ability to yield complex substituent patterns, which can be conducted in non-anhydrous solvents with easily accessible simple porphyrinoids.

One-pot synthesis of N-confused porphyrin-dipyrrin conjugates and their optical properties

A conjugated N-confused porphyrin-dipyrrin system NCP-IN-X (X = H, Br, Cl, OMe, COOEt) has been reported via N-Confused tetraphenylporphyrin (NCTPP) as a π-enlarged pyrrole and substituted trimethylindole subunits in 75-82% yields by one pot. All the NCP-INs show red-shifted absorption and emission in the NIR range compared with NCTPP in a series nonpolar and polar solvents. Interesting, relative higher emission in DMF can be observed. The structures of dipyrrin-NCP conjugates are characterized by ¹H-NMR and high resolution mass spectrum (HR-MS). Four frontier molecular orbital and simulated stick absorption spectra are calculated by DFT and TD-DFT calculation which is in good agreement with the experiments.

First imidazole-fused carbaporphyrinoid and its conversion to a N-heterocyclic carbene precursor

A series of novel imidazole-fused carbaporphyrinoids were obtained by a surprisingly simple approach by exploiting the reaction of tosylmethylisocyanide (TOSMIC) with readily obtainable 2-aza-21-carbaporphyrins. A facile methylation of silver(iii) complexes of these fused systems leads to cationic N-heterocyclic carbene precursors.

Copper-catalyzed synthesis of sulfonamides from nitroarenes via the insertion of sulfur dioxide

A three-component reaction of arylboronic acids, nitroarenes, and potassium metabisulfite under copper catalysis proceeds smoothly, giving rise to a range of sulfonamides in good to excellent yields with broad substrate scope.

Combinatorial synthesis and biological evaluations of (E)-β-trifluoromethyl vinylsulfones as antitumor agents

Combinatorial synthesis of (E)-β-trifluoromethyl vinylsulfones is accomplished through a reaction of alkynes, Togni reagent, and sodium benzenesulfinates in DMSO under metal-free conditions at room temperature. These compounds are evaluated in several assays against different tumor cells. Some hits are identified against ES-2, HO-8910, and K562.

Synthesis of β-Sulfonyl Amides through a Multicomponent Reaction with the Insertion of Sulfur Dioxide under Visible Light Irradiation

A multicomponent reaction of styrenes, aryldiazonium tetrafluoroborates, sulfur dioxide, nitriles, and water in the presence of a photocatalyst at room temperature is performed. This vicinal aminosulfonylation of styrenes with the insertion of sulfur dioxide under visible light irradiation proceeds efficiently with excellent chemoselectivity, giving rise to the corresponding β-sulfonyl amides in moderate to good yields.

Photoredox-catalyzed hydrosulfonylation reaction of electron-deficient alkenes with substituted Hantzsch esters and sulfur dioxide

A sulfonylation reaction of 4-substituted Hantzsch esters, DABCO·(SO₂)₂, and electron-deficient alkenes at room temperature in the presence of photoredox catalysis under visible light irradiation is described.

An unexpected reaction of aryldiazonium tetrafluoroborates, sodium metabisulfite, and thiourea under photoinduced conditions

A photoinduced synthesis of S-aryl thiosulfonates through a three-component reaction of aryldiazonium tetrafluoroborates, sodium metabisulfite, and thiourea is achieved. In this transformation, a radical coupling pathway is proposed.

Synthesis of β-hydroxysulfones through a copper(ii)-catalyzed multicomponent reaction with the insertion of sulfur dioxide

A copper(ii)-catalyzed aerobic oxidative reaction of arylhydrazines, DABCO·(SO₂)₂ and alkenes is reported. Diverse β-hydroxysulfones are generated in moderate to good yields through the hydroxysulfonylation of alkenes with the insertion of sulfur dioxide under mild conditions. In some cases, β-ketosulfones are produced.

Metal-catalyzed radical-type transformation of unactivated alkyl halides with C–C bond formation under photoinduced conditions

Recent advances in the metal-catalyzed radical-type transformation of unactivated alkyl halides with C–C bond formation under photoinduced conditions are summarized. Usually, a broad reaction scope is observed including tertiary, secondary, and primary alkyl halides, with good functional group compatibility.

Photoredox-catalyzed sulfonylation of alkenylcyclobutanols with the insertion of sulfur dioxide through semipinacol rearrangement

A photoredox-catalyzed sulfonylation of alkenylcyclobutanols with the insertion of sulfur dioxide through semipinacol rearrangement under visible light irradiation is developed.

Reaction of antiaromatic porphyrinoid with active methylene compounds

Antiaromatic norcorrolatonickel(ii) reacts regioselectively under basic conditions with active methylene compounds, yielding mono-substituted derivatives in which spectroscopic and redox properties of the starting macrocycle are retained.