Synthesis of Dibenz[b,f]oxepins via Manganese(III)-Based Oxidative 1,2-Radical Rearrangement

1O2 and Base Assisted Oxidative Conversion of β-Enaminoesters to α-Acyloxy-β-ketoesters under Visible Light Irradiation

Singlet oxygen (1O2) and base assisted conversion of β-enaminoesters to α-acyloxy-β-ketoesters is demonstrated under visible light irradiation. The reaction involves formation of an imine intermediate via ene-type pathway initiated by 1O2 followed by base promoted dimerization and hydrolysis steps. The method is mild, environmentally friendly, requires air as the oxidant, and gives the products in moderate to high yields.

Visible light induced cooperative carbonylation and (hetero)aryl migration: synthesis of multi-carbonyl compounds

Carbonylative transformation represents one of the most straightforward procedures for the synthesis of carbonyl-containing compounds. However, the carbonylative procedure toward 1,4-diketones is still limited which are key moieties with potent applications in various areas. Herein, we report a new strategy for the synthesis of multi-carbonyl compounds containing a 1,4-diketone skeleton through remote heteroaryl migration of traditionally restricted 1,3-migratory substrates utilizing carbon monoxide (CO) as the C1 synthon and diazonium compounds as the starting material.

Dibenzo[b,f]oxepine Molecules Used in Biological Systems and Medicine

In this short review, including 113 references, issues related to dibenzo[b,f]oxepine derivatives are presented. Dibenzo[b,f]oxepine scaffold is an important framework in medicinal chemistry, and its derivatives occur in several medicinally relevant plants. At the same time, the structure, production, and therapeutic effects of dibenzo[b,f]oxepines have not been extensively discussed thus far and are presented in this review. This manuscript addresses the following issues: extracting dibenzo[b,f]oxepines from plants and its significance in medicine, the biosynthesis of dibenzo[b,f]oxepines, the active synthetic dibenzo[b,f]oxepine derivatives, the potential of dibenzo[b,f]oxepines as microtubule inhibitors, and perspective for applications of dibenzo[b,f]oxepine derivatives. In conclusion, this review describes studies on various structural features and pharmacological actions of dibenzo[b,f]oxepine derivatives.

Strategies in the synthesis of dibenzo[b,f]heteropines

The dibenzo[b,f]azepine skeleton is important in the pharmaceutical industry, not only in terms of existing commercial antidepressants, anxiolytics and anticonvulsants, but also in reengineering for other applications. More recently, the potential of the dibenzo[b,f]azepine moiety in organic light emitting diodes and dye-sensitized solar cell dyes has been recognised, while catalysts and molecular organic frameworks with dibenzo[b,f]azepine derived ligands have also been reported. This review provides a brief overview of the different synthetic strategies to dibenzo[b,f]azepines and other dibenzo[b,f]heteropines.

Rearrangement of Methylenebis(cyclohexane-1,3-dione) Enols Induced by Mn(III)-Catalyzed Aerobic Oxidation

The Mn(III)-catalyzed aerobic oxidation of methylenebis(cyclohexane-1,3-dione) enols 1 resulted in 6a-hydroxy-2,3,4,6a,7,8,9,10a-octahydro-1H-benzo[c]chromene-1,6,10-triones 3 during the formation of 4,5,8,10,11,12-hexahydro-2H-benzo[b]oxecine-2,6,7,9(3H)-tetraones 2. The mechanism for the formation of 3 was proposed on the basis of the isolation of intermediates 2, which were transformed into 3 under Claisen and retro-Claisen conditions.

Radical-mediated rearrangements: past, present, and future

Rearrangement reactions, one of the most significant transformations in organic chemistry, play an irreplaceable role in improving synthetic efficiency and molecular complexity. Concomitant cleavage and reconstruction of chemical bonds can display the great artistry and the glamour of synthetic chemistry. Over the past century, ionic rearrangement reactions, in particular those involving cationic pathways, have represented most of the research. Alongside the renaissance of radical chemistry, radical-mediated rearrangements have recently seen a rapid increase of attention from the chemical community. Many new radical rearrangements that extensively reveal the migratory behaviour of functional groups have been unveiled in the last decade. This Review provides a comprehensive perspective on the area from the past to present achievements, and brings up the prospects that may inspire colleagues to develop more useful synthetic tools based on radical rearrangements.

One-Pot Synthesis of Dibenzo[b,f]oxepines and Total Synthesis of Bauhinoxepin C

In this work, we report a novel and simple one-pot synthesis of substituted dibenzo[b,f]oxepines under transition-metal-free conditions. This cascade process involves nucleophilic aromatic substitution followed by Knoevanagel condensation, as evidenced by the isolated reaction intermediates. We have also achieved the synthesis of anticancer bauhinoxepin C in 7 steps with 5.1% overall yield using this synthetic approach.

Electrochemical oxidative decarboxylation and 1,2-aryl migration towards the synthesis of 1,2-diaryl ethers

Carboxylic acid compounds are important chemicals and are widely present in various natural products. They are not only nucleophiles, but also radical precursors. Classic transition-metal-catalyzed and photochemical decarboxylation have shown their excellent site selectivity in radical chemistry. However, electrochemical decarboxylation with a long history hasn't got enough attention in recent years. In this work, the electrochemical oxidative decarboxylation and 1,2-aryl migration of 3,3-diarylpropionic acids have been introduced to construct C–O bonds with alcohols. Remarkably, this transformation can proceed smoothly without metal catalysts and external oxidants.

Carboxylic acid compounds are important chemicals and are widely present in various natural products. The conversion of carboxylic acids into valuable compounds is a promising field.

Synthesis of medium-sized (6-7-6) ring compounds by iron-catalyzed C-H activation/annulation [corrected]

In this report, we have described a FeCl3-catalyzed process involving intramolecular annulation of o-phenoxy diarylacetylenes via hydroarylation to afford a series of biologically potent fused seven-membered (6-7-6) ring compounds under mild reaction conditions. This reaction was believed to proceed through Friedel-Crafts type sequential carbometallation followed by protonation to produce phenyldibenz[b,f]oxepines. This method was also extended to synthesize seven-membered rings that are fused with coumarins.

Silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with malonyl peroxides in solvent-free conditions

For the first time silica gel was observed to activate peroxides in oxidative coupling reactions. Here we report silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with cyclic diacyl peroxides affording α-acyloxy derivatives with 100% atom efficiency. The highest yields of coupling products were achieved in solvent free conditions. C–O coupling products were prepared in yields up to 86%.

A metal-free yne-addition/1,4-aryl migration/decarboxylation cascade reaction of alkynoates with Csp3–H centers

Reactions of alkynoates with different types of radical precursors under metal-free conditions affording single-site-addition poly-substituted alkenes were reported.

Radical aryl migration reactions and synthetic applications

This review provides a comprehensive summary of radical aryl migration reactions, highlighting their mechanistic studies and synthetic applications.

Manganese triacetate as an efficient catalyst for bisperoxidation of styrenes

Bisperoxidation of styrenes with tert-butyl hydroperoxide in the presence of a catalytic amount of Mn(OAc)₃.