Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air

Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.

Decarboxylative, diastereoselective and exo-selective 1,3-dipolar cycloaddition for diversity-oriented construction of structurally spiro-[butyrolactone-pyrrolidine-chromanone] hybrids

Inspired by the chemistry and biology of butyrolactones, pyrrolidines and chromanones, herein we successfully developed a simple domino 1,3-dipolar cycloaddition of homoserine lactone-derived azomethine ylides for construction of biologically important spiro-[butyrolactone-pyrrolidine-chromanone] hybrids in the presence of the catalyst Et3N under mild conditions. It is based on the application of carboxylic acid activated chromones as dienophiles followed by a decarboxylation process. This reaction displayed good substrate tolerance and gave the desired products in moderate to good yields with high diastereoselectivities via an exo-transition state (up to 85% yield and >20:1 diastereomeric ratio). In particular, this is the first example of introduction of chromanone moiety into spiro [butyrolactone-pyrrolidine] frameworks, which might be valuable in medicinal chemistry.

Copper-Catalyzed Synthesis of Axially Chiral Biaryls with Diaryliodonium Salts as Arylation Reagents

NOBIN and BINAM derivatives harboring biaryl frameworks are recognized as a class of important atropisomers with versatile applications. Here, we present an efficient synthetic route to access such compounds through copper-catalyzed domino arylation of N-arylhydroxylamines or N-arylhydrazines with diaryliodonium salts and [3,3]-sigmatropic rearrangement. This reaction features mild conditions, good substrate compatibility, and excellent efficiency. The practicality of this protocol was further extended by the synthesis of biaryl amino alcohols.

Metal-free site-selective C–H cyanoalkylation of 8-aminoquinoline and aniline-derived amides with azobisisobutyronitrile

An efficient metal-free cyanoalkylation of 8-aminoquinoline and aniline-derived amides was achieved in the presence of K2S2O8. The method showed good substrate tolerance and also suitable for bromination and dimerization reactions.

Long-Term Stability of sulfhydryl-Au modification reagent in biological detection at room temperature

As a good substrate, gold has been widely applied in the fields of biological diagnosis and biological analysis. By forming Au-S bonds, the self-assembled molecules could form a monolayer modification...

Electrochemical synthesis of sulfonated benzothiophenes using 2-alkynylthioanisoles and sodium sulfinates

An electrochemical sulfonlylation/cyclization of 2-alkynylthioanisoles with sodium sulfinates was developed under catalyst-, external oxidant- and metal-free conditions. The electrosynthesis provides sustainable and efficient access to 3-sulfonated benzothiophenes with good substrate...

Decarboxylative-Mediated Regioselective 1,3-Dipolar Cycloaddition for Diversity-Oriented Synthesis of Structurally exo′-Selective Spiro[oxindole-pyrrolidine-dihydrocoumarin] Hybrids

A general and practical three-component regioselective 1,3-dipolar cycloaddition of 3-amino-oxindole-based azomethine ylides and coumarins has been developed. This reaction displayed good substrate tolerance and gave a diverse array of biologically relevant spiro[ox-­i­ndole-pyrrolidine-dihydrocoumarin] derivatives bearing four contiguous stereocenters including one spiro quaternary center in moderate to high yields (up to 90%) with high diastereoselectivities (up to 15:1 dr). It is based on the application of carboxylic acid activated coumarins as dienophiles followed by a decarboxylation process. The possible mechanism of the 1,3-dipolar cycloaddition is proposed via an exo′-transition state. Furthermore, this is the first example of decarboxylative-mediated regioselective 1,3-dipolar cycloaddition of 3-amino-oxindole-based azomethine ylides and coumarins.

Palladium-catalyzed cross-coupling reaction of sulfoxonium ylides and benzyl bromides by carbene migratory insertion

A palladium-catalyzed cross-coupling reaction of sulfoxonium ylides with benzyl bromides is reported, which could afford polysubstituted olefins and features good substrate tolerance.