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This article explores the synthesis of medium-sized lactones, which are important structural components in natural products and pharmaceuticals. The authors provide examples of specific lactones and their biological activities. They then discuss their own research on synthesizing benzannulated lactams and lactones using a specific starting material and different reaction conditions. The article includes a table summarizing their experimental results, demonstrating the formation of various lactones. The authors conclude by discussing the implications and potential applications of their findings. The study was supported by Evonik Industries, and the authors express gratitude to individuals who assisted in the laboratory. [Extracted from the article]

This article explores the stabilization of carbenium ions and their role in bond reorganizations, with a specific focus on the β-silicon effect. It discusses the generation of cyclopropyl-stabilized silylium ions and their reactivity in bond reorganization processes, including various rearrangements involving vinylcyclopropanes. The article provides insights into the mechanisms and outcomes of these reactions and discusses their potential applications in the synthesis of silicon-containing compounds. The authors also investigate different variations of substituents and nucleophilic coupling partners, highlighting the importance of careful reaction conditions in obtaining specific products. [Extracted from the article]

For the insertion of amino acid derivatives, the Fmoc protecting group strategy was used (SuRE method B), with both - and -amino acids again being compatible ( B 25 b , B 31 b - B 34 b ). Using this method, I N i -acylation of B 21 b using the more stable Fmoc-protected amino acid chloride B 22 b proceeded well (based on full consumption of B 21 b by TLC analysis) to form imide B 23 b (Scheme 3). It is clear that lactam B 21 b undergoes I N i -acylation less readily than lactam B 8 b , and in previous work we have found Cbz-protected amino acid chlorides to be less stable than the analogous Fmoc derivatives. Keywords: macrocycles; medium-sized rings; ring expansion; natural product analogues; lactams; lactones; solomonamides EN macrocycles medium-sized rings ring expansion natural product analogues lactams lactones solomonamides 1694 1698 5 08/18/23 20230901 NES 230901 Graph Solomonamides A and B were first isolated in 2011 by Zampella and coworkers from the marine sponge I Theonella swinhoei i . [Extracted from the article]

The transition-metal-free total syntheses of the oxygenated carbazole natural products glycoborine, carbazomycin A and carbazomycin B are reported. The key step involves an NBS-mediated cyclobutanol ring expansion to 4-tetralones for the preparation of the tricyclic carbazole core. [ABSTRACT FROM AUTHOR]

Domino conjugate addition/inert-bond activation is a useful strategy for improving the efficiency of synthesis. We summarize reports on domino conjugate addition/inert-bond activation and its applications in the rhodium-catalyzed ring-expansion and ring-opening reactions of azetidines. 1 Introduction 2 Rhodium-Catalyzed Domino Conjugate Addition/β-C Cleavage/ Protonation 3 Rhodium-Catalyzed Domino Conjugate Addition/N-Directed α-C(sp3)–H Activation 4 Conclusion [ABSTRACT FROM AUTHOR]

We report the rearrangement of abietane core with trifluoromethanesulfonic anhydride in pyridine to afford the icetexane core, a key intermediate for total syntheses of the structurally intriguing and biologically active compounds (±)-barbatusol, (±)-rosmaridiphenol, and (±)-pisiferin. [ABSTRACT FROM AUTHOR]

Cyclic polymers are of increasing interest to the synthetic and physical polymer communities due to their unique structures that lack chain ends. This topological distinction results in decreased chain entanglement, lower intrinsic viscosity, and smaller hydrodynamic radii. Many methods for the production of cyclic polymers exist, however, large-scale production of architecturally pure cyclic polymers is challenging. Ring-expansion metathesis polymerization (REMP) is an increasingly promising method to produce cyclic polymers because of the mild and scalable reaction conditions. Herein, a brief history of REMP for the synthesis of cyclic polymers with both ruthenium and non-ruthenium initiators is discussed. Even though REMP is a promising method for synthesizing cyclic polymers, state-of-the-art methods still struggle with poor molar mass control, slow polymerization rates, low conversion, and poor initiator stability. To combat these challenges, our group has developed a tethered ruthenium-benzylidene initiator, CB6, which utilizes design features from ubiquitous Grubbs-type initiators used in linear polymerizations. These structural modifications are shown to improve initiator kinetics, enhance initiator stability, and increase control over the molar mass of the resulting cyclic polymers. 1 Introduction 2 Ring-Expansion Metathesis Polymerization (REMP) with Ruthenium Initiators 3 New Developments in Ruthenium Ring-Expansion Metathesis (REMP) Initiator Design 4 Ring-Expansion Metathesis Polymerization (REMP) with Non-Ruthenium Initiators 5 Conclusions [ABSTRACT FROM AUTHOR]

The current Account gives an insight into the synthesis of some N-heterocyclic β-amino acid derivatives and various functionalized saturated azaheterocycles accessed from substituted cycloalkenes via ring C=C bond oxidative cleavage followed by ring closing across double reductive amination. The ring-cleavage protocol has been accomplished according to two common approaches: a) Os-catalyzed dihydroxylation/NaIO4 vicinal diol oxidation and b) ozonolysis. A comparative study on these methodologies has been investigated. Due to the everincreasing relevance of organofluorine chemistry in drug research as well as of the high biological potential of β-amino acid derivatives several illustrative examples to the access of various fluorine-containing piperidine or azepane β-amino acid derivatives are also presented in the current Account. 1 Introduction 2 Olefin-Bond Transformation by Oxidative Ring Cleavage 3 Synthesis of Saturated Azaheterocycles via Oxidative Ring-Opening/Ring-Closing Double Reductive Amination 3.1 Importance of Fluorine-Containing Azaheterocycles in Pharmaceutical Research 3.2 Synthesis of Azaheterocyclic Amino Acid Derivatives with a Piperidine or Azepane Framework through Oxidative Ring Opening/Reductive Amination 3.2.1 Synthesis of Piperidine β-Amino Esters 3.2.2 Synthesis of Azepane β-Amino Esters 3.2.3 Synthesis of Fluorine-Containing Piperidine γ-Amino Esters 3.3 Synthesis of Tetrahydroisoquinoline Derivatives through Oxidative Ring Opening/Reductive Amination Protocol 3.4 Synthesis of Functionalized Benzazepines through Reductive Amination 3.4.1 Synthesis of Benzo[ c ]azepines 3.4.2 Synthesis of Benzo[ d ]azepines 3.5 Synthesis of Various N-Heterocycles via Ozonolysis/Reductive Amination 3.5.1 Synthesis of Compounds with an Azepane Ring 3.5.2 Synthesis of Piperidine β-Amino Acids and Piperidine-Fused β-Lactams 3.5.3 Synthesis of γ-Lactams with a Piperidine Ring 3.5.4 Synthesis of other N-Heterocycles 4 Summary and Outlook 5 List of Abbreviations [ABSTRACT FROM AUTHOR]

Vinyl aziridines are versatile starting materials toward ring-expansion transformations. Such processes are widely used to give various medium or larger N-heterocycles of synthetic interest. This letter describes a copper-catalyzed ring expansion of vinyl aziridines to 3-pyrrolines by using a Cu(I) salt [(CuOTf)2 ·toluene or Cu(MeCN)4 ·PF6 ]. In particular, this transformation occurs under mild conditions (THF, rt). [ABSTRACT FROM AUTHOR]

The only cyclic α-diazocarbonyl compound employed in the Büchner–Curtius–Schlotterbeck ring expansion of cyclic ketones to date was α-diazo-γ-butyrolactone. Encouraged by the recent success using α-diazo acetamides in related Tiffeneau–Demjanov type ring expansions, we extended this approach to various α-diazo-γ-butyrolactams, which produced, under BF3 ·OEt2-promoted conditions, spirocyclic seven-membered ketones. These findings substantially enhance the possibilities offered by cyclic α-diazocarbonyl compounds in constructing privileged spirocyclic scaffolds for drug design. [ABSTRACT FROM AUTHOR]

Macrocycles and medium-sized rings have important applications in several scientific fields but can be challenging to make using traditional end-to-end cyclization reactions. Ring-expansion methods represent a useful alternative and offer numerous practical benefits. In this Account, we discuss the current state of the art of ring-expansion strategies that have been applied consecutively. Such methods have the power to expedite the design and synthesis of functionalized macro-cycles via the selective, iterative insertion of smaller fragments into ring-enlarged products. 1 Introduction 2 Insertion Reactions 2.1 Transamidation/Transpeptidation 2.2 Transesterification 2.3 Transthioesterification 2.4 Aminyl Radical Cascade 2.5 Iterative Synthesis of Lactones 2.6 Successive Ring Expansion of β-Ketoesters and Lactams 3 Pericyclic Reactions 3.1 Sulfur-Mediated Rearrangements 3.2 Nitrogen-Mediated Rearrangements 4 Fragmentation Reactions 5 Conclusions and Future Outlook [ABSTRACT FROM AUTHOR]

Lipase B from Candida antarctica catalyzes the oxidative ring expansion of furfuryl alcohols using aqueous hydrogen peroxide to yield functionalized pyranones under mild conditions. The method further allows for the preparation of corresponding piperidinone derivatives by enzymatic rearrangement of N-protected furfurylamines. [ABSTRACT FROM AUTHOR]

N-Heterocyclic carbene catalysis allows the rapid formation of functionalized carbon-carbon bonds. Our group has spent the previous decade focusing on broadening practical applications of this type of catalysis. The design and discovery of novel reactivities and catalysts in our group can best be divided into work focusing on the Stetter, ringexpansion, and cross-benzoin reactions. Along with our expansion of the reaction scope, our introduction of novel bis(amino)cyclopropenylidene catalysts for the Stetter reaction successfully suppresses formation of side products, increasing synthetic utility. Concurrent work on ring-expansion reactions allows access to functionalized lactones and lactams. In addition to expanding the scope of the cross-benzoin reaction through use of α-ketoesters and α-amino aldehydes, the introduction of a new triazolylidene catalyst has allowed access to general chemoselective cross-benzoin reactions between aliphatic and aromatic aldehydes. 1 Introduction 2 Stetter Reactions 2.1 Domino Stetter Reactions 3 Ring-Expansion Reactions 4 Cross-Benzoin Reactions 5 Summary and Outlook. [ABSTRACT FROM AUTHOR]

Hyperforin has remained a popular and challenging synthetic target since its isolation over forty years ago. As a result, numerous synthetic strategies and ring-forming reactions have been developed to address its formidable molecular architecture. Herein we describe our contributions to this area resulting in a ten-step synthetic pathway enabled by a novel diketene annulation reaction and oxidative ring expansion strategy. [ABSTRACT FROM AUTHOR]

The synthesis and preliminary ADME evaluation of novel 4-(trifluoromethyl)-5,7,8,9-tetrahydro-6H-pyrido[3,2-b]azepin- 6-ones is presented. The key step is a ring expansion of 4-(trifluoromethyl)- 7,8-dihydroquinolin-5(6H)-ones via a Beckmann rearrangement. The rearrangement opens up possibilities to access novel unexplored scaffolds for medicinal chemistry. The biopharmaceutical profiling revealed a strong structural dependency of the druglike properties. [ABSTRACT FROM AUTHOR]

The synthesis of pharmacologically relevant isoquinoline-tetrazoles and benzazocine-tetrazoles via sequential azido-Ugi and alkyne-induced ring-expansion reactions starting from cotarnine chloride are reported. A one-pot, multicomponent reaction protocol toward the ring-expanded product is also described. [ABSTRACT FROM AUTHOR]

A formal [3+2] cycloaddition between aziridines and alkenes to give the corresponding pyrrolidines was successfully carried out in the presence of a cationic manganese porphyrin catalyst. The use of the porphyrin catalyst allowed, for the first time, styrene derivatives to react with aziridines. [ABSTRACT FROM AUTHOR]

In the last decade, chemists have increasingly focused on the development of new and more efficient methods for the catalytic conversion of carbon dioxide into value-added organic molecules. Homogeneous catalysis has proved to be a key technology for the conversion of carbon dioxide under particularly mild reaction conditions that meet the increasing societal demands for sustainable chemical processing. In this account article, we focus on the most effective routes developed for ring expansion-addition reaction of carbon dioxide to epoxides mediated by either metal catalysts or organocatalyst systems to give cyclic organic carbonates. [ABSTRACT FROM AUTHOR]

The direct combination of the desymmetrization of Nheterocyclic meso-diols using lipase from Mucor miehei as biocatalyst and subsequent ring expansion of the optically active products by activation of the remaining hydroxy group gives rise to functionalized nonsymmetrical piperidines in a highly enantio- and diastereoselective manner. [ABSTRACT FROM AUTHOR]

Synthetic studies on a 17ß-hydroxysteroid dehydrogenase type 3 (17ß-HSD3) inhibitor are described. The unsymmetrical dibenzazocine skeleton was constructed by a regiocontrolled ring-expansion reaction of a cyclic oxime with DIBAL-H. [ABSTRACT FROM AUTHOR]

This account summarizes the Njardarson group ring expansion journey from early vinyl oxirane explorations to the latest vinyl oxetane ring expansion discoveries. The evolution of the program and incredible success of Cu(hfacac)2 as catalyst is detailed. Application of these new ring expansion reactions to natural product, pharmaceutical and commodity chemical targets is discussed as well as our intriguing mechanistic journey and interesting entry into the world of chiral counterion catalysis. [ABSTRACT FROM AUTHOR]

An organocatalyzed enantioselective desymmetrization reaction for converting 3-substituted cyclobutanones into 4-substituted 5-hydroxy-γ-lactams is presented. This involves a ring-expanding O-nitroso aldol-cyclization domino sequence. This synthetic protocol provides access to five-membered ring systems in good yields with the generation of two new stereogenic centers. [ABSTRACT FROM AUTHOR]

A very short route to 2-phenylpiperidin-3-ol derivatives and 3-hydroxypipecolic acids is described. The approach uses two key steps: a one-pot reduction/Grignard addition sequence applied to alkyl proline esters and a ring expansion applied to the corresponding prolinols. [ABSTRACT FROM AUTHOR]

Cyclobutanes derived from [2+2] photocycloaddition �reactions of tetronic acid esters were subjected to free-radical fragmentation reactions. The product formation was strongly dependent on the relative stabilities of the intermediate radicals, thus leading to either an oxepane or a methylenetetrahydrofuran in good yields. [ABSTRACT FROM AUTHOR]

Ring-expansion reactions of bicyclic vinylidenecyclopropanes in the presence of Lewis acid was investigated, providing an efficient method for the synthesis of naphthalenes with annulated carbocycles of various ring sizes in good to excellent yields under mild conditions. [ABSTRACT FROM AUTHOR]

Stereoselective and regioselective synthesis of functionalized seven- and eight-membered carbocyclic systems was achieved by the ring expansion-cleavage of readily prepared [3.2.1] and [3.3.1] bicyclic alcohols using alkoxy radical fragmentation at room temperature. Transannular migration in the cyclooctane �system explain formation of unusual products. [ABSTRACT FROM AUTHOR]

N-Sulfonyl pyridinones derived from α-furylsulfon�amides may be aromatised with concomitant N→O sulfonyl transfer to produce 3-sulfonyloxypyridines. [ABSTRACT FROM AUTHOR]

The treatment of optically active prolinols with DAST produces optically active 3-fluoropiperidines via aziridinium intermediates. [ABSTRACT FROM AUTHOR]

The titanium-mediated cyclopropanation of an easily prepared chiral a-siloxylactone leads efficiently to an enantiomerically pure cyclopropanol derivative. The trimethylsilyl trifluoro�methane sulfonate induced pinacol rearrangement allows high level of chirality transfer into a cyclobutanone, which is a useful intermediate in the total synthesis of (+)-grandisol. [ABSTRACT FROM AUTHOR]

A diastereoselective approach to bicyclo[3.2.1]octan-2-ones and -3-ones is achieved by means of the semi-pinacol rearrangement of 2,3-epoxy silyl ethers. The key 1,2-migration is stereospecific. This method is easily amenable to an enantioselective synthesis by utilizing nonracemic norcamphor and related compounds. [ABSTRACT FROM AUTHOR]

A simple, efficient and general method has been developed for the synthesis of 1-arenesulfonylazetidines through a one-pot reaction of 1-arenesulfonylaziridines with dimethylsulfoxonium methylide, generated under microwave irradiation, using alumina as solid support. [ABSTRACT FROM AUTHOR]

Benzyne inserts into one of the C-O bonds of styrene �oxide to form a dihydrobenzofuran as the major product together with five other reaction products. A detailed study of the reaction mixture clarified an intriguing forty-year-old personal communication from Stiles and Haag. [ABSTRACT FROM AUTHOR]

A novel and efficient approach to prepare dihydropyrans via the ring expansion of cyclopropylidene alcohols in the presence of NaI in AcOH-MeCN was reported. The key feature in the transformation is the effect of the iodide anion. [ABSTRACT FROM AUTHOR]