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This article explores the olefination of carbonyl compounds, which is an important process in synthetic research for the preparation of alkenes. The article discusses various reagents and mechanisms involved in olefination reactions, including the use of organophosphorus compounds, silanes, boranes, and titanium organometallics. The authors also investigate the potential involvement of ß-lactones, specifically activated carboxylic esters, in carbon-based olefination reactions. The study presents experimental results using esters of fluorinated alcohols and carbonyl compounds, demonstrating the formation of ¿-methylcinnamates through the formation and spontaneous cleavage of ß-lactones. This research suggests that carbon-based reagents can react similarly to heteroatom-based reagents in olefination reactions. [Extracted from the article]

This article discusses the development of a highly enantioselective synthesis of α-substituted γ-lactones bearing a γ-quaternary stereocenter through catalytic asymmetric bromolactonization. The researchers used chiral bifunctional sulfide catalysts to achieve this synthesis, and they demonstrated the utility of the method through various transformations of the resulting γ-lactone products. The article highlights the importance of these α-substituted γ-lactones as building blocks for the preparation of biologically active compounds. The researchers are currently exploring further applications of their chiral bifunctional sulfide catalysts in other asymmetric syntheses. [Extracted from the article]

This article explores the synthesis of 3-lactone-substituted 2-oxindoles with vicinal quaternary carbon centers through vinylogous conjugate addition. These compounds have various bioactivities and are important intermediates in the synthesis of natural products and pharmaceuticals. The authors discuss different methods and catalysts used for this synthesis, including diastereo- and enantioselective versions that allow for the preparation of optically active natural products. They also propose a method to connect lactones and indol-2-ones to create new molecules. The article includes a table presenting the optimization of reaction conditions. The authors found that a chiral N,N'-dioxide/nickel(II) complex was effective in promoting the vinylogous addition reaction, yielding high diastereo- and enantioselectivities. They also conducted a gram-scale synthesis to demonstrate the practicality of the approach. [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]

After synthesizing alkyne hydrazones B 5a b through a simple condensation of I p i -toluenesulfonylhydrazide with the alkyne hydrazones, the resulting compounds can react with NIS to synthesize B 7a b I via i a chemoselective pathway; compound B 7a b can be easily hydrolyzed, leading to alkyne hydrazides B 6a b . Keywords: tandem reactions; N -iodosuccinimide; lactones; tosylhydrazones; alkynes; oxidation EN tandem reactions N -iodosuccinimide lactones tosylhydrazones alkynes oxidation 1270 1274 5 06/19/23 20230704 NES 230704 Tandem C-C and C-X bond formations are among the most powerful approaches for the construction of a broad spectrum of structurally complex molecules from readily available starting materials in a convergent way. In the case of B 3a b synthesis, the 5- I exo i -dig cyclization is preferred over the 6- I endo i -dig cyclization; however, in the case of B 2a b synthesis, the 6- I endo i -dig cyclization is the main pathway for the cyclization step. Owing to the significance of pyranoquinoline and isobenzofuran moieties, which are known to be present in a variety of alkaloids and possess a wide range of pharmacological and biological activities, [6] we report herein the tandem oxidation-ring closure reactions of alkyne hydrazones to afford fused lactones by using NIS in the presence of water. [Extracted from the article]

We report an asymmetric inverse-electron-demand Diels–Alder reaction of electron-deficient 2-pyrones with various phenyl vinyl selenides catalyzed by a chiral bis(oxazoline)/Cu(OTf)2 complex. By using a side-arm-modified chiral bis(oxazoline)ligand, a variety of [2,2,2]-bicyclic lactones with phenyl selenide substituents were obtained in good to excellent yields (up to 99%) and enantioselectivities (up to 98% ee) under mild conditions. Based on this strategy, a highly concise enantioselective synthesis of the Corey lactone was accomplished. [ABSTRACT FROM AUTHOR]

o -Iodoxybenzoic acid (IBX) is an oxidation reagent that has surged into prominence in the last two decades. It is cost-effective, environmentally benign, and readily prepared from o -iodobenzoic acid. However, its insolubility in common organic solvents and explosive attributes upon impact and heating are debilitating disadvantages. The development of modified IBX s (mIBX s) that exhibit improved solubility and enhanced reactivity, and obviate explosive attributes by judicious manipulation of the structure of IBX has been an incessant endeavor. In this account, common organic solvent-soluble mIBX s developed in our research group are collated with a discussion of the rationale underlying the design principles. Steric build-up around the iodoxolone moiety that is responsible for strong intermolecular interactions within the crystal lattice of IBX constitutes the key consideration in the design and development of modified λ5-iodanes that are reactive and sparingly soluble in common organic solvents. In situ generation of mIBX s from precursor iodo-acids in the presence of Oxone® permits their employment as organocatalysts for facile oxidative transformations. Reactive mIBX s generated in situ from precursor modified iodo-acids (mIA s, II) in the presence of Oxone® may offer unrivaled prospects for cost-effective oxidations. Applications of mIBX s, generated in situ or otherwise, for efficient oxidations are consolidated. 1 Introduction 2 Design and Synthesis of Modified IBXs and their Precursors Iodo-Acids 3 Catalytic Oxidations with Modified IBXs 3.1 Oxidation of Alcohols 3.2 Oxidation of 1,2-Diols 3.3 Conversion of Diols into Lactones 3.4 One-Pot Oxidative Cleavage of Olefins 3.5 One-Pot Transformation of Olefins into α-Bromo- and α-Azidoketones 4 Conclusions [ABSTRACT FROM AUTHOR]

Two catalytic benzannulation/1,4-addition cascades of available enynones with indoles or tetronic acid-derived enamino lactones as C-nucleophiles are reported, producing 53 examples of heterocycle-incorporating diarylmethanes with moderate to excellent yields. The combination of AgOTf and Sc(OTf)3 permits bimetallic synergistic catalysis of the reaction of enynones with indoles to access 35 triarylmethanes in generally good yields with ortho -naphthoquinone methides, generated in situ, as the key intermediates. Exchanging indoles for tetronic acid-derived enamino lactones resulted in 18 diarylmethanes by the Ag-catalyzed benzannulation/1,4-addition cascade. Both reactions are advantageous for their high atom utilization and mild reaction conditions, providing intriguing complementary approaches for the direct syntheses of new heterocycle-containing diarylmethanes. [ABSTRACT FROM AUTHOR]

Electrosynthesis is undergoing a renaissance, but it is still far from being considered a standard method within the chemists' synthetic toolbox. In this article, we will demystify organic electrochemistry by reviewing some practical methodologies developed in our laboratory to prepare highly reactive synthetic intermediates. 1 Introduction 2 Acyloxy Radicals 3 Orthoesters 4 Isocyanates 5 Isocyanides 6 Diazo Compounds 7 Conclusion [ABSTRACT FROM AUTHOR]

α-Metalated isocyanides are a versatile class of compounds that can easily be employed in various transformations, affording tangible libraries for screening campaigns. We report the ring-opening reactions of cyclic anhydrides and lactones with three different metalated isocyanides that readily give 4,5-disubstituted oxazoles, including useful drug-like synthetic intermediates with two functional groups as handles for further modifications. [ABSTRACT FROM AUTHOR]

For a long time, frogs were believed to communicate primarily via the acoustic channel, but during the last decades it became obvious that various lineages also use chemical communication. In this Account we present our research on the identification of volatile lactones from Madagascan Mantellidae and African Hyperoliidae frogs. Both possess male specific glands that can disseminate a range of volatile compounds. Key constituents are macrocyclic lactones. They show high variability in structure and occurrence. We focus here on the synthetic approaches we have used to clarify constitution and configuration of the glandular compounds. Key synthetic methods are ring-closing metathesis and nucleophilic epoxide opening. Often, but not always, the natural compounds occurs in amounts that excludes their investigation by NMR spectroscopy. Instead, we use GC/MS analysis, GC/IR, microreactions, and synthesis to identify such components. Several aspects of our work will be described giving some insight in our scientific approach. 1 Introduction 2 Macrocylic Lactones from the Fatty Acid Biosynthetic Pathway 3 Unsaturated Lactones 4 Terpenoid Lactones 5 Macrolide Occurrence 6 Conclusions [ABSTRACT FROM AUTHOR]

Inspired by the chemistry and biology of butyrolactones, pyrrolidines, and chromanones, we successfully developed a simple domino 1,3-dipolar cycloaddition of homoserine-lactone-derived azomethine ylides for the construction of biologically important spiro[butyrolactone–pyrrolidine–chromanone] hybrids in the presence of Et3 N as a catalyst under mild conditions. The reaction 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 (up to 85% yield and >20:1 diastereomeric ratio) via an exo -transition state. This is the first example of an introduction of a chromanone moiety into a spiro[butyrolactone-pyrrolidine] framework, which might be valuable in medicinal chemistry. [ABSTRACT FROM AUTHOR]

Diels–Alder reactions of 2-pyrones with alkenes can provide highly functionalized [2,2,2]-bicyclic lactones under mild reaction conditions. Synthetic utilizations of these reactions have been well demonstrated in natural-product synthesis. Although several catalytic asymmetric strategies have been realized, current research in this area is still largely underdeveloped. Recent advances in enantioselective inverse-electron-demand Diels–Alder reactions with Lewis acid catalysis are reviewed. 1 Introduction 2 State of the Art of Enantioselective Diels–Alder Reactions of 2-Pyrones by Lewis Acid Catalysis 3 Enantioselective Synthesis of Arene cis -Dihydrodiols by Diels–-Alder/Retro-Diels–Alder Reactions of 2-Pyrones 4 Enantioselective Synthesis of cis -Decalin Derivatives by Diels–-Alder Reactions of 2-Pyrones 5 Conclusions [ABSTRACT FROM AUTHOR]

Benzimidazoles represent common chemical moieties in bioactive compounds. The synthesis of this heterocycle often involves a condensation of an ortho -phenylenediamine with a carboxylic acid derivative. The observed dialkylation of the starting ortho -phenylenediamine is avoided by opening of lactones or lactams. This strategy can directly yield 1 H -benzimidazoles substituted at the 2-position by a functionalized chain. We present herein a study of the effect of different electron-withdrawing or electron-donating groups at the 4-position of ortho -phenylenediamines on the opening of lactones or lactams to synthesize benzimidazol-2-yl alkanols and benzimidazol-2-yl alkylamines. [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]

A lactonization of various diols catalyzed by platinum on carbon (Pt/C) in water under an atmosphere of molecular oxygen was developed. Derivatives of 1,4- 1,5- and 1,6-diols were transformed into the corresponding five-, six-, and seven-membered lactones by the present oxidative lactonization method. [ABSTRACT FROM AUTHOR]

A catalytic enantioselective α-amination reaction of alkenoate cyclic esters with dialkyl azodicarboxylates was achieved by using a 3,3′-di(1-naphthyl)-substituted (R)-BINOL–dibromostannane complex as a chiral precatalyst in the presence of a sodium alkoxide and an alcohol. Optically active α-hydrazino ketones were obtained in moderate to high yields and with up to 91% ee in the presence of the chiral tin alkoxide generated in situ. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated that variants of a heme protein, Rhodothermus marinus cytochrome c (Rma cyt c), catalyze abiological carbene boron–hydrogen (B–H) bond insertion with high efficiency and selectivity. Here we investigated this carbon–boron bond-forming chemistry with cyclic, lactone-based carbenes. Using directed evolution, we obtained a Rma cyt c variant BORLAC that shows high selectivity and efficiency for B–H insertion of 5- and 6-membered lactone carbenes (up to 24,500 total turnovers and 97.1:2.9 enantiomeric ratio). The enzyme shows low activity with a 7-membered lactone carbene. Computational studies revealed a highly twisted geometry of the 7-membered lactone carbene intermediate relative to 5- and 6-membered ones. Directed evolution of cytochrome c together with computational characterization of key iron-carbene intermediates has allowed us to expand the scope of enzymatic carbene B–H insertion to produce new lactone-based organoborons. [ABSTRACT FROM AUTHOR]

A new synthetic methodology for azaspiro-γ-lactones is reported. The key C–H spirolactonization was accomplished by employing iodobenzene diacetate and potassium bromide to afford a variety of azaspiro-γ-lactones in high yields. The reaction was also applicable to the preparation of a bislactone derivative. [ABSTRACT FROM AUTHOR]

A formal total synthesis of the anticancer natural product kanamienamide has been accomplished. This communication describes two approaches to the macrocyclic core of the natural product. The key features of the route include an efficient macrolactamization, a Corey–Bakshi–Shibata asymmetric reduction, and a Stork–Zhao–Wittig olefination. [ABSTRACT FROM AUTHOR]

The synthesis of 6-substituted 3-fluoro-5,6-dihydropyran-2- ones under mild conditions is described. The key step of the synthesis involves a Julia–Kocienski olefination. [ABSTRACT FROM AUTHOR]

A highly stereoselective conjugate radical addition to arylidene ketones and lactones has been developed. The conjugate radical additions using chiral salen Lewis acids proceeds with up to 99:1 dr and 87% ee in good to excellent chemical yields. [ABSTRACT FROM AUTHOR]

(HMe2SiCH2)2 has been utilized as a useful reagent for B(C6F5)3-catalyzed reduction–lactonization of keto acids to synthesize γ- and δ-lactones. The process led concisely to (–)-cis-whisky and (–)-ciscognac lactones in respective overall yields of 32% and 36%. [ABSTRACT FROM AUTHOR]

N-Alkyl pipecolamides were efficiently synthesized from D-glucurono-6,3-lactone via a key 5-azido N-alkylamide intermediate that can be used as a scaffold for the synthesis of 4-amino and N-sulfonated pipecolamide derivatives. [ABSTRACT FROM AUTHOR]

Acyclic conjugated ynenediones tethered to an alcohol or carboxylic acid are converted into furanyl-substituted cyclic ethers or lactones in a single step by treatment with the tetrahydrothiophene. Modest levels of diastereocontrol can be achieved in some cases where the presence of a substituent on the tether results in the creation of a second stereogenic centre upon formation of the cyclic ether or lactone. [ABSTRACT FROM AUTHOR]

The advantages of glycosyl donors bearing a 2,6-lactone moiety in 1,2-cis-β-glycosylation reactions are discussed in the context of recent comprehension on the SN2-SN1 borderline. The 2,6-lactone structure increases the likelihood of the SN2-like reaction, analogous to 4,6-tethered structures or 2-O-electron-deficient substituents, which are known to mound the energetic barrier to SN1 reactions. Furthermore, the glycosyl cation generated from the 2,6-lactone donor seems to direct β-glycosides similar to the torsional and flipped cations generated from 4,6-tethered donors and mannuronate or 3,6-lactone donors, respectively. Overall, 2,6-lactones are suitable for use in 1,2-cis-β-glycosylations, and this novel class of donors is expected to help deepen our global understanding of glycosylation reactions. 1 Introduction 2 Stereoinversion (SN2-Like) Reactions 3 Conformational Control of Glycosyl Cations 4 Conclusions. [ABSTRACT FROM AUTHOR]

The catalytic asymmetric intramolecular cyclopropanation (CAIMCP) of α-diazo-α-silyl acetates to form oxabicyclo[3.2.1]hexane, which proceeds with high yields and enantioselectivities, is described. The maximum enantiomeric excess observed was 96% ee and the absolute configuration of the products was elucidated. The counteranion of the Cu(I) catalyst was found to play a crucial role in determining the yields and enantioselectivities, with highly anionic counteranions improving both yields and enantioselectivities. Our previously reported model explains the enantiofacial selectivity of the reacting alkene. [ABSTRACT FROM AUTHOR]

The electrophilic substitution of indoles with tetronic acid and N-acetyltetramic acid mediated by BF3·OEt2 was investigated. This strategy allowed for the preparation of nine indole-substituted furan-2-ones (indolyl-γ-lactones) and 3-pyrrolin-2-ones (indolyl-γ-lactams) and is more straightforward than previously reported synthetic methods. During the course of our investigation, we also discovered a facile synthesis of tetronates and a tetramate via a BF3-mediated addition of alcohols to tetronic acid and N-acetyltetramic acid, respectively. [ABSTRACT FROM AUTHOR]

A palladium(II)-catalyzed intramolecular lactonization of unactivated methylene C(sp³)-H bonds using PIP bidentate auxiliary is described. This method provides an efficient and concise pathway to synthesize functionalized γ-lactones. [ABSTRACT FROM AUTHOR]

Amine-functionalized polyesters are an important class of materials for biomedical applications due to their utility in gene and drug delivery, bioconjugation reactions, hydrogels, and controlled release systems. The synthesis of amino polyesters by ring-opening polymerization (ROP) is an ongoing challenge that is being aided by advances in reaction development. For the benefit of this important research area, this article highlights the related works of synthesizing amino polyesters by ROP as well as our recent synthesis of a new library of amino polyesters from amine-functionalized lactone monomers. 1 Polymerization of Lactone Monomers with Unprotected Amine Functionalities. 2 Synthesis of Amino-Functionalized Polyesters via Postpolymerization Modification of Functionalized Monomers. 3 Design of Novel Amino-Functionalized Lactone Monomers and Direct Synthesis of Amino Polyesters. [ABSTRACT FROM AUTHOR]

Biphenyl-2,6-diols, substituted at the C2' position with alkanoic acid side chain containing a stereogenic center, underwent the highly atrop-stereoselective nine-membered lactone formation with differentiation of the diastereotopic hydroxy groups. [ABSTRACT FROM AUTHOR]

Lactone-moiety-attached 2-cyclohexylideneethyl picolinate was prepared through the OH-directed epoxidation (98% ds) of (R)-3-methylcyclohex-2-en-1-ol (99% ee), Horner-Wadsworth-Emmons olefination, conversion to the allylic moiety, and epoxide ring opening with Et2AlCH2CO2t-Bu. The allylic substitution of the picolinate with Me2CuMgBr·MgBr2 furnished a quaternary carbon center with 92% ds. Finally, the lactonization of the product, the tert-butyl ester of the seco acid, under acidic conditions, afforded (--)-anastrephin. [ABSTRACT FROM AUTHOR]

The naturally occurring polyphenolic compounds, valoneic and woodfordinic acid dilactones, were synthesized through the classical Ullmann coupling reaction as the key step. To prepare the diaryl ether component, the Ullmann condensation method was applied using the corresponding phenol and arylbromide. [ABSTRACT FROM AUTHOR]

A new method for the preparation of optically active α-methylidene-γ-lactones is presented. The developed strategy utilizes an intramolecular Rauhut-Currier reaction for a facile construction of the α-methylidene-γ-lactone framework. The reaction is catalyzed by a chiral phosphine and employs the principles of nucleophilic catalysis. It benefits from operational simplicity and uses readily available starting materials. [ABSTRACT FROM AUTHOR]

We previously reported a bifunctional organic catalyst that promotes highly efficient enantioselective halolactonizations of a broad array of olefinic acids. As part of that work, we demonstrated the desymmetrization of a prochiral substrate through a catalytic enantioselective halolactonization, and we report herein the application of one such desymmetrization process to the syntheses of F-ring subunit synthons of (+)-kibdelone C. [ABSTRACT FROM AUTHOR]

A variety of polysubstituted δ-lactones containing three or four stereocenters were prepared from various dialkyl 2-(3-oxo-1,3-diarylpropyl) malonates by a Barbier-type zinc-mediated allylation or cyclohexenylation of the keto group, followed by intramolecular lactonization/ transesterification. The stereochemistry of the major isomers was confirmed by X-ray crystal structure analysis of representative compounds. [ABSTRACT FROM AUTHOR]

Cyclocondensation of alicyclic and heterocyclic α-hydroxy β- dicarbonyl compounds with dimethyl malonate gives bicyclic butenolide derivatives. The reaction sequence is catalyzed by 4-(N,N-dimethylamino) pyridine and consists of two processes: Knoevenagel condensation followed by transesterification. Depending on the chemical nature of the β-dicarbonyl moiety (oxoester, diketone or α-acetyl lactone or lactam), products with either annulated or spirocyclic constitution are obtained. [ABSTRACT FROM AUTHOR]

Substituted γ-butyrolactones represent an important group of structural fragments commonly found in natural products, receptor ligands, and drug molecules. Interest in preparing a library of substituted γ-butyrolactones and finding that limited routes to β-substituted lactones exist, led to the development of an efficient approach for the synthesis of β,β-disubstituted γ-butyrolactones. Readily prepared substituted 1,4-diols and γ-hydroxy olefins were treated with the RuCl3/NaIO4 oxidation system to provide the target β,β-disubstituted γ-butyrolactones in modest to good yields. The reaction goes through a lactol intermediate that was isolated and characterized for selected compounds. The approach supplies an efficient and versatile method for the synthesis of these important heterocyclic structures. Importantly, the present work is the first report that demonstrates the ability of RuCl3/NaIO4 to selectively oxidize primary hydroxyl groups in the presence of secondary alcohols to prepare lactones in good yields. [ABSTRACT FROM AUTHOR]

Substituted γ-butyrolactones represent an important group of structural fragments commonly found in natural products, receptor ligands, and drug molecules. Interest in preparing a library of substituted γ-butyrolactones and finding that limited routes to β-substituted lactones exist, led to the development of an efficient approach for the synthesis of β,β-disubstituted γ-butyrolactones. Readily prepared substituted 1,4-diols and γ-hydroxy olefins were treated with the RuCl3/NaIO4 oxidation system to provide the target β,β-disubstituted γ-butyrolactones in modest to good yields. The reaction goes through a lactol intermediate that was isolated and characterized for selected compounds. The approach supplies an efficient and versatile method for the synthesis of these important heterocyclic structures. Importantly, the present work is the first report that demonstrates the ability of RuCl3/NaIO4 to selectively oxidize primary hydroxyl groups in the presence of secondary alcohols to prepare lactones in good yields. [ABSTRACT FROM AUTHOR]

A divergent strategy has been used to concisely and efficiently complete the synthesis of (+)-mintlactone and (-)-isomintlactone via SmI2-induced intramolecular radical cyclization, two rings and a stereocenter were constructed in one step. In the synthesis, the stereochemistry of the final natural product is set relative to the stereocenter of (-)-citronellol and favored coordination transition state of samarium atom with substrate. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed nucleophilic allylation of aldehydes with vinylcyclopropane in the presence of diethylzinc proceeded to provide homoallyl alcohols with anti stereoselectivity. Aldimines prepared from aldehyde and primary amines in situ underwent a similar nucleophilic allylation to give homoallylamines with syn stereoselectivity. The resulting homoallyl alcohols and homoallylamines could be converted by treatment with a tetranuclear zinc cluster into γ-vinyl-δ-valerolactones and γ-vinyl-δ-valerolactams, respectively. [ABSTRACT FROM AUTHOR]

Halocyclization reactions such as halolactonization are powerful synthetic methods for the functionalization of alkenes and alkynes. However, asymmetric versions were thought of as difficult reactions and only recently have new asymmetric, organocatalytic halocyclization methods been reported. Herein, we examine a specific strategy for asymmetric halocyclization reactions, desymmetrizing cyclizations, and highlight recent contributions in this area. [ABSTRACT FROM AUTHOR]

A detailed account regarding the synthesis of 5-ylidene-2(5H)-furanones is given. The key step is a decarboxylative Knoevenagel-type reaction of tetronamides with various α-functionalized aldehydes. The synthesis of protected basidalin is presented. [ABSTRACT FROM AUTHOR]

An efficient, one-pot method for the highly chemoselective synthesis of δ-lactols from α,β-unsaturated δ-lactones using CuCl and NaBH4 in methanol was developed. [ABSTRACT FROM AUTHOR]

A new and efficient approach to a series of highly fluorescent non-aggregating donor-acceptor 1,8-naphthyridines is described. Examination of the photophysical properties of the 1,8-naphthyridines revealed that the presence of donor-acceptor functionality leads to bright green fluorescence with solvatochromism in solvents of differing polarities. The application of these molecules in metal sensing was also explored. [ABSTRACT FROM AUTHOR]

It was found that α-aryl-α-diazocarboxylates react with variable regioselectivity in intramolecular rhodium-catalyzed C-H insertion reactions. 3-(Trialkoxysilyl)propyl esters underwent a clean cis-γ-lactone formation (62-69%) if the aryl rest was a phenyl group while the analogous α-(2-bromophenyl)-α-diazocarboxylates produced the respective βlactones. In general β-lactone formation was shown to be the only detectable C-H insertion pathway for the latter substrate class irrespective of the ester substituent. The β-lactone products (eight examples) were obtained in yields of 41-68% with a diastereomeric ratio (dr) of 75:25 to 96:4 in favor of the trans diastereoisomer. The 2-bromo substituent could be displaced by an aryl group in a subsequent Suzuki cross-coupling reaction. [ABSTRACT FROM AUTHOR]

An access to the dioxabicyclo[3.2.1]octane core of sorangicin A was developed, using a keto lactone formation, a Mukaiyama-Michael reaction and an epoxide opening as the key steps. [ABSTRACT FROM AUTHOR]

The first copper-catalyzed reductive aldol addition/lactonization domino reactions of α,β-unsaturated dicarboxylate esters with ketones were achieved in high yields. The method, which involves easily available reagents, a flexible combination of reactants, and mild conditions, provides a simple route to functionalized lactones bearing an ester group. [ABSTRACT FROM AUTHOR]

A new catalytic system for the asymmetric Baeyer-Villiger oxidation of monosubstituted prochiral cyclobutanones to γ-butyrolactones with high yields (40-99%) and enantioselectivities (45-87%) is described. Aluminium complexes with biaryl ligands and ionic liquids are presented. The incorporation of an ionic liquid in the complex structure was confirmed by the observed fourcoordinate nature of the aluminium. [ABSTRACT FROM AUTHOR]

Efficient synthesis of medium- and large-ring lactones is an important topic in organic synthesis. Summarized here are the conventional approaches and two recently reported new strategies. The both new intermolecular reactions employ siloxy alkynes as the key reaction partner. Enabled by the design of new (1,6)-amphoteric molecules and unprecedented ring expansion of fused oxetenium species, the two processes not only provide new solutions to medium- and large-ring lactone synthesis, but also overcome the drawbacks of traditional intramolecular cyclization strategies that typically require high dilution or slow addition. [ABSTRACT FROM AUTHOR]