Regioselective and Switchable meso-Aminations and Couplings of 5,15-Diarylchlorins

Phenyliodine bis(trifluoroacetate) as a sustainable reagent: exploring its significance in organic synthesis

Iodine-containing molecules, especially hypervalent iodine compounds, have gained significant attention in organic synthesis. They are valuable and sustainable reagents, leading to a remarkable surge in their use for chemical transformations. One such hypervalent iodine compound, phenyliodine bis(trifluoroacetate)/bis(trifluoroacetoxy)iodobenzene, commonly referred to as PIFA, has emerged as a prominent candidate due to its attributes of facile manipulation, moderate reactivity, low toxicity, and ready availability. PIFA presents an auspicious prospect as a substitute for costly organometallic catalysts and environmentally hazardous oxidants containing heavy metals. PIFA exhibits remarkable catalytic activity, facilitating an array of consequential organic reactions, including sulfenylation, alkylarylation, oxidative coupling, cascade reactions, amination, amidation, ring-rearrangement, carboxylation, and numerous others. Over the past decade, the application of PIFA in synthetic chemistry has witnessed substantial growth, necessitating an updated exploration of this field. In this discourse, we present a concise overview of PIFA's applications as a 'green' reagent in the domain of synthetic organic chemistry. A primary objective of this article is to bring to the forefront the scientific community's awareness of the merits associated with adopting PIFA as an environmentally conscientious alternative to heavy metals.

An Oxidant- and Catalyst-Free Electrooxidative Cross-Coupling Approach to Synthesize meso-Substituted Porphyrin Derivatives

The synthesis of porphyrin and chlorin derivatives has attracted significant attention due to their numerous applications. Herein, we report an environment friendly oxidant- and catalyst-free electrooxidative cross-coupling approach for multiple coupling reactions to synthesize meso C-N, C-O, and C-S substituted porphyrin and chlorin derivatives. For C-N cross-coupling reactions, diaminated porphyrins were obtained as the main products, while using 4-bromo-2,6-dimethyl aniline resulted in monoaminated product. Similarly, electrochemical catalysis of porphyrins with phenol and thiophene produced meso-disubstituted porphyrins in moderate yields under a smaller current. Chlorins were also applicable, and 20-substituted products were efficiently produced regioselectively. To the best of our knowledge, this work represents the first example of electrooxidative C-X cross-coupling of porphyrins and chlorins.

Regioselective C-H amination of free base porphyrins via electrogenerated pyridinium-porphyrins and stabilization of easily oxidized amino-porphyrins by protonation

Four free base aminoporphyrins were synthesized in two steps via regioselective anodic nucleophilic substitution with pyridine followed by ring opening of the electrogenerated pyridinium with piperidine. The X-ray crystallographic structure of the unstable 2-aminotetraphenylporphyrin was solved. Protonation of this latter compound leads to the stable diiminium porphyrin salt.

2,3-Dicyano-5,6-dichlorobenzoquinone-Mediated and Selective C-O and C-C Cross-Couplings of Phenols and Porphyrins

A selective C-O cross-coupling reaction between porphyrins and phenols has been developed through 2,3-dicyano-5,6-dichlorobenzoquinone (DDQ)/Sc(OTf)₃ oxidation, efficiently delivering meso-etherified porphyrins in good yields (≤93%). The radical complex process was proposed and calculated as the rationalized mechanism to block the homocoupling process. In addition, the switchable selective C-C cross-coupling reaction was achieved by using bulky electron-rich phenols and naphthols under DDQ oxidation conditions.

Reactions of 2-aza-21-carbaporphyrin with aniline derivatives

Post-synthetic modification of N-confused porphyrin (NCP) yields chiral 21-arylazo- or 3,21-bis(arylamino)-NCP in one-step, one-pot reactions of NCP with anilines.