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A strategy for synthesis of γ-alkylated enones through oxidative coupling of siloxydienes and 1,3-dicarbonyl compounds is reported. This method is an interrupted form of our formal [3 + 2] cycloaddition method reported previously. The present work excels in generating all-carbon quaternary centers via C–C bond formation at the remote γ-site which is traditionally challenging to functionalize. Stereoselectivity and functional group tolerance are examined in complex systems. Double alkylation reactions are also described.

Neopeapyran ( 1 ), an unusual furo[2,3 b ]pyran analogue, together with a new cyclopeptide, turnagainolide C ( 2 ), were isolated from Streptomyces sp. S2236 associated with the rhizosphere soil of Panax notoginseng . The planar structure and relative configuration of neopeapyran ( 1 ) were elucidated on the basis of spectroscopic techniques, while the absolute configuration was determined by TDDFT calculation. The absolute configuration of turnagainolide C ( 2 ) was determined by partial hydrolysis, together with the advanced Marfey's method and spectroscopic analysis. The antimicrobial activities of these two compounds were also investigated.

A novel strategy for the difunctionalization of styrenes was developed. This synthesis includes the use of electrophilic perfluoroalkyl and tert-butylperoxy radicals and produces (1-(tert-butylperoxy)-2-perfluoroalkyl)ethylbenzene at room temperature, which has been traditionally difficult to synthesize. With at least four radical species included in the transformation, its high chemoselectivity was extraordinary; the results were further elucidated using computational studies. The methodology also holds a good potential for application as a result of its mild reaction conditions, ease of further modification, and insensitivity to moisture and air.

A general regio- and stereoselective γ-C–C bond formation is achieved using α-halocarbonyl compounds and dienol ethers via Cu(II) catalysis. This method constitutes a novel approach to the challenging 1,6-dioxygenation motif. A range of γ-substituted enones, including many bearing all-carbon quaternary centers, are available through a simple protocol under mild reaction conditions with superb functional group compatibility. Excellent stereoinduction is observed providing controlled access to challenging stereochemical arrays.

An asymmetric carbene cascade reaction, which proceeds through carbene/alkyne metathesis and formal (3+2) cycloaddition and converts alkynyl-tethered enol diazoacetates to chiral bicyclic cyclopentadienes, is presented; and no catalytic asymmetric version of these carbene cascade transformations has been disclosed so far. The proton signals of the cyclopropene intermediates are observed in the mechanism study, which clearly demonstrate the reaction pathways. In addition, these products are intercepted via Diels–Alder reactions to provide bridged polycyclic structures in high yields and enantioselectivities.

A practical and efficient method for the direct, regioselective conversion of vinylogous esters to haloresorcinols is reported. Control of the reaction conditions enables synthesis of either the 4- or 6-haloresorcinol isomers from a common precursor with excellent regiocontrol and high yield. The generality and functional group tolerance of this novel protocol is demonstrated. The utility of this methodology to access polyhaloresorcinols is also reported. These methods create useful functionalized building blocks for further synthetic applications.

A transition-metal-free oxidative N–N bond formation strategy was developed to generate various structurally interesting [1,2,4]triazolo[1,5-a]benzazoles efficiently. The mechanism of the key oxidative N–N bond formation was investigated by using an intramolecular competition reaction. Notably, the first single crystal structure was also obtained to confirm the structure of 2-aryl[1,2,4]triazolo[1,5-a]benzimidazole.

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction regiospecifically produces 1,4-disubstituted-1,2,3-triazole molecules. This heterocycle formation chemistry has high tolerance to reaction conditions and substrate structures. Therefore, it has been practiced not only within, but also far beyond the area of heterocyclic chemistry. Herein, the mechanistic understanding of CuAAC is summarized, with a particular emphasis on the significance of copper/azide interactions. Our analysis concludes that the formation of the azide/copper(I) acetylide complex in the early stage of the reaction dictates the reaction rate. The subsequent triazole ring-formation step is fast and consequently possibly kinetically invisible. Therefore, structures of substrates and copper catalysts, as well as other reaction variables that are conducive to the formation of the copper/alkyne/azide ternary complex predisposed for cycloaddition would result in highly efficient CuAAC reactions. Specifically, terminal alkynes with relatively low pKa values and an inclination to engage in π-backbonding with copper(I), azides with ancillary copper-binding ligands (aka chelating azides), and copper catalysts that resist aggregation, balance redox activity with Lewis acidity, and allow for dinuclear cooperative catalysis are favored in CuAAC reactions. Brief discussions on the mechanistic aspects of internal alkyne-involved CuAAC reactions are also included, based on the relatively limited data that are available at this point.

The increase and spread of Gram-negative bacteria that resistant are to almost all currently available β-lactam antibiotics is a major global health problem. The primary cause for drug resistance is the acquisition of metallo-β-lactamases such as metallo-β-lactamase-1 (NDM-1). The fungal natural product aspergillomarasmine A (AMA), a fungal natural product, is an inhibitor of NDM-1 and has shown promising in vivo therapeutic potential in a mouse model infected with NDM-1-expressing Gram-negative bacteria. The first total synthesis and stereochemical configuration reassignment of aspergillomarasmine A is reported. The synthesis highlights a flexible route and an effective strategy to achieve the required oxidation state at a late stage. This modular route is amenable to the efficient preparation of analogues for the development of metallo-β-lactamase inhibitors to potentiate β-lactam antibiotics.

Reported is the first scalable synthesis of rac-jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6-dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6-dienyne reductive radical cyclization.

A radical-based strategy for regioselective γ-C-C bond formation/oxa-conjugate addition, forming the tetrahydrobenzofuran core common to many bioactive natural products is described. The technique utilizes readily available enone derivatives and 1,3-dicarbonyl compounds as coupling partners in an oxidative formal [3+2] cycloaddition mediated by Mn(III) . The transformation delivers polycyclic products in good yields and proceeds with complete regiocontrol and excellent stereoselectivity. Sterically encumbered substrates are notably well-tolerated and bond formation occurs readily to form neopentyl and all-carbon quaternary centers in good yields. Several stereo- and chemoselective transformations of the products are described.

A general and efficient synthesis of the 2H-tetrahydro-4,6-dioxo-1,2-oxazine ring system through a tandem nucleophilic addition and transesterification reaction is described. The reaction is highly functional-group-tolerant and proceeds under mild conditions, affording the corresponding products in good to excellent yields. This method represents the first general synthetic route to access this heterocyclic scaffold, which exists in the complex natural products alchivemycin A and B with significant antibiotic activities.

Carbonyl compounds bearing a γ-amino group are valuable pharmacologically active targets. Regioselective γ-C–N bond formation is achieved with simple enone substrates through controlled dienolate reactivity toward azodicarboxylate electrophiles. The amination reaction occurs readily with sterically demanding nucleophiles and is stereoselective.

A preformed chiral boron-complex including a VANOL-type ligand is efficiently employed as catalyst for the enantioselective Diels—Alder reaction of 2-hydroxychalcones [cf.

A variety of distally Csp3-chlorinated ketones are synthesized with good regioselectivities via silver-catalyzed ring opening of cycloalkanols under mild reaction conditions. The reaction uses only routine, inexpensive reagents and can be scaled up to gram quantities. A novel radical-mediated C–C bond cleavage/C–Cl bond formation is proposed.

Through merging Cu-based carbenes in a radical process, a novel crossover reaction has been successfully established, leading to the facile and efficient syntheses of various γ-peroxy esters and 1,4-dicarbonyl compounds. Considering that both Cu-based carbene complexes and radicals are extremely reactive, and therefore exist only in extraordinarily low concentrations, the high selectivity of this coupling reaction is unusual.

A regioselective synthesis of 1-tetralones via silver-catalyzed ring expansion is described. A variety of 1-tetralones are furnished under mild reaction conditions from tertiary cyclobutanols regardless of the electronic properties and steric hindrance of substituents, providing a new and practical method to access diverse 1-tetralone building blocks. Preliminary experimental and DFT studies revealed that a radical-mediated sequence of C–C bond cleavage/C–C bond formation is involved.

A regioselective method for the introduction of sulfonyl groups at the γ-carbon of enone systems is reported. Using a copper catalyst and readily available sulfonyl chlorides, a range of silyl dienol ethers are sulfonylated in good yield under mild reaction conditions. The sulfone derivatives formed are poised for further synthetic manipulations as demonstrated by regioselective alkylations.

Tripterlides A–F (1–6), six new abietane diterpenoid derivatives, together with six known abietane diterpenoids (7–12) were obtained from the leaves of Tripterygium wilfordii. Tripterlides A–C (1–3) were novel 14(13 → 12),18(4 → 3)-diabeo-abietanoids possessing a 6/6/5 tricyclic ring system. These unusual structures, including their absolute configurations, were determined from UV, IR, HRESIMS, 1D and 2D-NMR data and through comparisons of their experimental and calculated electronic circular dichroism (ECD) spectra. A plausible biosynthetic pathway for 1–3 was proposed. Furthermore, in an in vitro bioassay, 5, 6, 8, and 10–12 showed significant cytotoxic effects against five human cell lines, and 6, 8, 10–12 also exhibited moderate inhibitory activities on hypoxia-inducible factor 1 (HIF-1), which is relevant to tumor development.

This review summarizes the application of different strategies for the key Diels–Alder cycloaddition in prenylflavonoid and related Diels–Alder natural products synthesis, highlighting the application of novel methodologies and innovative strategies in the synthesis of these natural products and their analogues. 1 Introduction 2 Classical Conditions for the Diels–Alder Cycloaddition 2.1 Thermal Promotion 2.2 High-Pressure Promotion 2.3 Bronsted Acid Catalysis 3 Modern Approaches to the Diels–Alder Cycloaddition 3.1 Electron-Transfer Initiation 3.2 Silver-Nanoparticle Catalysis 3.3 Chiral-Boron-Complex Promotion 4 Conclusion

New chiral zirconium systems catalyze the asymmetric hydroamination/cyclization of primary aminoalkenes affording five- and six-membered N-heterocyclic amines with up to 94% e.e.

The first examples of regioselective cyclocondensation of hetereocyclic ketene aminals with nitrophenylpropiolates are described.

ZnO nanorods and nanowires (50-120 nm diameter, 1-6 μm length) are prepared on SiO2 substrate by catalyst-free thermal evaporation using Zn powders in an Al2O3 boat (900 °C).

The title phosphors are prepared by solid state reaction using CaCO3, M2CO3 (M: Li, Na, K), TiO2, Eu2O3, and Bi2O3 as source materials (600 °C for 5 h and 1350 °C for 4 h in air).

Nine guaiane-type sesquiterpenes, as an example compound (I) is shown, and one eudesmane-type sesquiterpene (II), called argyinolides, are isolated from the title plant together with nine known analogues.

Oligomeric sesquiterpenoids, biogenetically assembled from two or three monomeric sesquiterpenoid units via diverse pathways, represent a unique class of natural products. The synthetic studies inspired by their biogenesis have offered significant impetus for the efficient construction of these architecturally complex frameworks. Here we provide an overview for the biomimetic syntheses of these dimeric and trimeric molecules based on the different strategies of bond formation, including Diels-Alder reaction, hetero-Diels-Alder reaction, [2 + 2] cycloaddition, and C-C bond coupling.

The simple one-pot cycloaddition/decarbonylation/dehydrogenation sequence of two indenones allows the synthesis of benzo[c]fluorenone derivatives.

In contrast to established C-H functionalizations of tertiary amines involving α-aminoalkyl radicals the present method does not require photocatalytic conditions or a transition-metal catalyst.An α-aminoalkyl radical and benzoyl cyanide are the key intermediates in this process.

18 Title compounds are prepared and evaluated for antiproliferative activities against five human cancer cell lines.

Red single crystals of the new title compound are prepared by stoichiometric solid state reaction of Hg2Cl2, red P, and Cu (evacuated Pyrex tube, 1.

The first example of oxidative olefination via Pd-catalyzed C4-H activation of CF3- and CF2H-substituted pyrazoles is reported.