Bioinspired Selective Synthesis of Heterodimer 8-5' or 8-O-4' Neolignan Analogs

Visible-light TiO2-catalyzed synthesis of dihydrobenzofurans by oxidative [3 + 2] annulation of phenols with alkenyl phenols

An oxidative strategy for the preparation of dihydrobenzofurans via heterogeneous photocatalysis is reported. This method leverages the surface interaction between the alkenyl phenol and the TiO2 solid surface, which enables direct activation by visible light without the need for pre-functionalization or surface modification. The resulting alkenyl phenoxyl radical is proposed to be selectively captured by a neutral phenol nucleophile, rendering β-5' coupling with excellent chemo- and regio-selectivity. The reaction proceeds under benign conditions, using an inexpensive, nontoxic, and recyclable photocatalyst under visible light irradiation with air as the terminal oxidant at room temperature.

Development of novel transition metal-catalyzed synthetic approaches for the synthesis of a dihydrobenzofuran nucleus: a review

The synthesis of dihydrobenzofuran scaffolds bears pivotal significance in the field of medicinal chemistry and organic synthesis. These heterocyclic scaffolds hold immense prospects owing to their significant pharmaceutical applications as they are extensively employed as essential precursors for constructing complex organic frameworks. Their versatility and importance make them an interesting subject of study for researchers in the scientific community. While exploring their synthesis, researchers have unveiled various novel and efficient pathways for assembling the dihydrobenzofuran core. In the wake of extensive data being continuously reported each year, we have outlined the recent updates (post 2020) on novel methodological accomplishments employing the efficient catalytic role of several transition metals to forge dihydrobenzofuran functionalities.

Recent advances in oxidative phenol coupling for the total synthesis of natural products

Covering: 2008 to 2023This review will describe oxidative phenol coupling as applied in the total synthesis of natural products. This review covers catalytic and electrochemical methods with a brief comparison to stoichiometric and enzymatic systems assessing their practicality, atom economy, and other measures. Natural products forged by C-C and C-O oxidative phenol couplings as well as from alkenyl phenol couplings will be addressed. Additionally, exploration into catalytic oxidative coupling of phenols and other related species (carbazoles, indoles, aryl ethers, etc.) will be surveyed. Future directions of this particular area of research will also be assessed.

Electrosynthesis of 5-Aminocoumaran Derivatives from Olefins and Aminophenols

The electrochemical synthesis of 5-aminocoumaran derivatives from easily oxidizable aminophenols and readily available olefins is described. The reaction efficiently produces 5-aminocoumarans in high yield under mild and environmentally friendly conditions without the necessity of catalysts, additives, oxidizing agents, or sacrificial reagents. Hydrogen as the sole byproduct of the reaction makes the method clean, highly atom-efficient, and step-economical.

Chemodivergent Photocatalyzed Heterocyclization of Hydrazones and Isothiocyanates for the Selectivity Synthesis of 2-Amino-1,3,4-thiadiazoles and 1,2,4-Triazole-3-thiones

A photocatalytic chemodivergent reaction for the selectivity formation of C-S and C-N bonds in a controlled manner was proposed. The reaction medium, either neutral or acidic, is critical to dictate the formation of 2-amino-1,3,4-thiadiazoles and 1,2,4-triazole-3-thiones from isothiocyanates and hydrazones. This is a practical protocol to achieve the chemoselectivity under mild and metal-free conditions.

Visible-Light-Induced Oxidative Coupling of Phenols and Alkenylphenols with a Recyclable, Solid Photocatalyst

A photocatalytic method for phenol and alkenylphenol oxidative coupling is reported using an inexpensive heterogeneous titanium dioxide photocatalyst with air and visible light. During the coupling process, the Ti-substrate complex is activated under visible light through a ligand to metal charge transfer effect, and the diphenol adduct is proposed to form through a radical cation. The heterogeneous TiO2 catalyst remains stable throughout the reaction and can be easily removed and reused multiple times.

Cu(ii)-Catalyzed C2-site functionalization of p-aminophenols: an approach for selective cross-dehydrogenative aminations

Site selective cross dehydrogenative aminations from precursors without preactivated C–H and N–H bonds have been challenging.

Cu-Catalyzed Synthesis of Benzoxazole with Phenol and Cyclic Oxime

A Cu-catalyzed straightforward synthesis of benzoxazoles from free phenols and cyclic oxime esters is reported. The mild reaction conditions tolerate various electron-withdrawing and electron-donating functional groups on both substrates, affording benzoxazoles in moderate to good yields. With this protocol, large-scale syntheses of Ezutromid and Flunoxaprofe in one or two steps are demonstrated. A catalytic mechanism, which includes Cu-catalyzed amination via inner-sphere electron transfer and consequent annulation, is proposed.