Post-functionalization of dibenzothiophene to functionalized biphenyls via a photoinduced thia-Baeyer-Villiger oxidation.

The Baeyer-Villiger reaction is used extensively in organic chemistry. Sila- and bora-variants have also been documented widely, with these processes underpinning, for example, the Fleming-Tamao oxidation and hydroborative alkene hydration, respectively. By contrast, the development of thia-Baeyer-Villiger reactions involving sulfoxides has long been considered unlikely because competitive oxidation to the sulfone occurs exclusively. Here, we disclose a photoinduced thia-Baeyer-Villiger-type oxidations; specifically, we find that exposure of dibenzothiophene (DBT) derivatives to an iron porphyrin catalyst under Ultraviolet irradiation in the presence of t-BuOOH generates sulfinic esters in up to 87% yield. The produced sulfinic esters are transformed to a variety of biphenyl substrates including biphenyl sulfoxides, sulfones and sulfonamides in 1-2 steps. These results provide a mild process for the selective functionalization of sulfur compounds, and offer a biomimetic approach to convert DBT into 2-hydroxybiphenyl under controllable stepwise pathway. Based upon experimental evidences and DFT calculation, a mechanism is proposed.

Unique Thia-Baeyer-Villiger-Type Oxidation of Dibenzothiophene Sulfoxides Derivatives.

The present research has demonstrated that selective C-S bond cleavages of dibenzothiophene and its derivatives are feasible by thia-Baeyer-Villiger type oxidation, i. e. the oxygen insertion process within a sulfoxide-carbon linkage, in the presence of porphyrin iron (III) and by ultraviolet irradiation originating from sunlight, high pressure Hg-lamp or residentially germicidal ultraviolet lamp under very mild conditions. This reaction with tert-butylhydroperoxide at 30.0 °C leads to dibenzo[1,2]oxathiin-6-oxide (PBS) in 83.2 % isolated yield or its hydrated products, 2-(2-hydroxyphenyl)-benzenesulfinic derivatives (HPBS) in near 100 % yield based HPLC data. PBS and HPBS are a type of biological products detected on the C-S bond cleavage step through various oxidative biodesulfurization (OBDS) pathways, and are useful synthetic intermediates and fine chemicals. These observations may contribute on understanding delicately molecular aspect of OBDS in the photosynthesis system, expanding the C-S cleavage chemistry of S-heterocyclic compounds and approaching toward biomemic desulfurization with respect to converting sulfur contaminants to chemically beneficial blocks as needed and performing under the ambient conditions.

Synthesis of Diketones, Ketoesters, and Tetraketones by Electrochemical Oxidative Decarboxylation of Malonic Acid Derivatives: Application to the Synthesis of cis-Jasmone.

Disubstituted malonic acid derivatives are smoothly converted into diketones and ketoesters in good to excellent yield (68% to 91%) under electrochemical conditions. The scope can be extended to transform trisubstituted bis-malonic acids into tetraketones in 77% to 86% yield. The new method was applied to the total synthesis of cis-jasmone.

Electrochemical methoxymethylation of alcohols - a new, green and safe approach for the preparation of MOM ethers and other acetals.

A new, green, safe, cost-effective and highly efficient electrochemical approach for the methoxymethylation of alcohols and phenols was successfully developed. The methodology was also applied to the synthesis of substituted acetals.

Straightforward and effective synthesis of γ-aminobutyric acid transporter subtype 2-selective acyl-substituted azaspiro[4.5]decanes.

Supply of major metabolites such as γ-aminobutyric acid (GABA), ß-alanine and taurine is an essential instrument that shapes signalling, proper cell functioning and survival in the brain and peripheral organs. This background motivates the synthesis of novel classes of compounds regulating their selective transport through various fluid-organ barriers via the low-affinity γ-aminobutyric acid (GABA) transporter subtype 2 (GAT2). Natural and synthetic spirocyclic compounds or therapeutics with a range of structures and biological activity are increasingly recognised in this regard. Based on pre-validated GABA transport activity, straightforward and efficient synthesis method was developed to provide an azaspiro[4.5]decane scaffold, holding a variety of charge, substituent and 3D constrain of spirocyclic amine. Investigation of the azaspiro[4.5]decane scaffold in cell lines expressing the four GABA transporter subtypes led to the discovery of a subclass of a GAT2-selective compounds with acyl-substituted azaspiro[4.5]decane core.

User-Friendly Platinum Catalysts for the Highly Stereoselective Hydrosilylation of Alkynes and Alkenes.

With a view to addressing the shortcomings of traditional catalysts, a new generation of outstanding N-heterocyclic carbene platinum(0) complexes for the hydrosilylation of unsaturated carbon-carbon bonds is reported. Their discovery and application to the stereoselective addition of various silanes to silylated alkynes, terminal acetylenes, and olefins is presented. Insights into the catalytic cycle and the origin of the stereoselectivity are also discussed.

Electrochemical Oxidative Decarboxylation of Malonic Acid Derivatives: A Method for the Synthesis of Ketals and Ketones.

A novel electrochemical oxidative decarboxylation of disubstituted malonic acids leading to dimethoxy ketals is described. In the presence of NH3, a wide range of disubstituted malonic acids was transformed into the corresponding ketals in good to excellent yields under electrochemical conditions. When the crude reaction mixture, obtained after electrolysis, was directly treated with 1 M aq HCl, the initially generated ketals were smoothly transformed into the corresponding ketones in a single vessel operation.

Validation of the boronate sensor ContPY1 as a specific probe for fluorescent detection of hydrogen peroxide in plants.

Studying the implication of hydrogen peroxide in biological processes in plants remains a challenge due to the current shortcomings of H2O2-responsive probes. The use of ContPY1, a new fluorescent probe, which is highly selective and sensitive for H2O2, was investigated. To validate the use of ContPY1 on plants, we have generated protocols employing cells suspensions and leaves, and measured specifically H2O2 production by plants using spectrofluorometry and microscopy.

Anionic cascade reactions. One-pot assembly of (Z)-chloro-exo-methylenetetrahydrofurans from ß-hydroxyketones.

The assembly of (Z)-chloro-exo-methylenetetrahydrofurans by an original and connective anionic cascade sequence is reported. Base-catalysed condensation of ß-hydroxyketones with 1,1-dichloroethylene generates, in moderate to good yields, the corresponding (Z)-chloro-exo-methylenetetrahydrofurans. Acidic treatment of this motif leads to several unexpected dimers, possessing unique structural features.

Preparation of highly functionalised benzofurans from ortho-hydroxyphenones and dichloroethylene: applications and mechanistic investigations.

Highly functionalised benzofurans have been prepared from ortho-hydroxyphenones and 1,1-dichloroethylene. The key intermediate, a chloromethylene furan, smoothly rearranged into the corresponding benzofuran carbaldehyde under acidic conditions. Some mechanistic investigations have been performed and several biologically active benzofurans have been synthesised.

Interaction network of antimicrobial peptides of Arabidopsis thaliana, based on high-throughput yeast two-hybrid screening.

One mechanism used by plants to respond to infection is the production of antimicrobial peptides (AMPs). In addition to a role in defence, AMPs seem to have other biological functions. Furthermore, the number of cysteine-rich AMP-like peptides appears to have been underpredicted in plant genomes. Such peptides could be involved in plant defence and/or in other biological processes. Here we generated an interaction network between 15 AMPs/AMP-like peptides and ca. 8000 other Arabidopsis thaliana proteins (AtORFeome2.0) and found 53 putative novel interactions. These interactions involve five transcription factors, a subunit of the COP9 signalosome, a heat shock protein, a MAP kinase kinase, a thioredoxin and 4 uncharacterized proteins.

Evidence of two key intermediates contributing to the selectivity of P450-biomimetic oxidation of sulfides to sulfoxides and sulfones.

A mild process for the selective oxidation of sulfides is in great demand. Therefore, probing the mechanism underlying the biological oxidation of sulfides under ambient conditions may provide valuable insights for the development of such a reaction. Based on porphyrin models of P450 enzymes, evidence of two key intermediates, Int0 and Int1, in this reaction is provided. Spectroscopic studies indicated the formation of a hydroperoxide-iron(III) species (Int0) upon addition of H(2)O(2). This intermediate proved to be highly selective for sulfoxide production. By contrast, a defined porphyrin oxoiron(IV) cation radical (Int1) directly reacted with sulfoxides, leading selectively to the corresponding sulfones. Interestingly, the available sulfoxides reversibly act as a new axial ligand for Int0 forming a more active species Int0(SO). The amount of Int0 increased in the presence of alkyl, aryl, or aromatic sulfides, while Int1 formed in the absence of these sulfides. Thus, sulfoxides and sulfones would selectively form under conditions that favor the corresponding intermediates, which elucidate the biological oxidation pathway.

Functionalized orthoesters as powerful building blocks for the efficient preparation of heteroaromatic bicycles.

By combining substituted anilines with functionalized orthoesters, an efficient and connective methodology for the preparation of benzoxazole, benzothiazole, and benzimidazole derivatives has been established. The versatility of this approach enables the development of new libraries of heterocycles containing multifunctional sites.

Efficient and connective assembly of highly functionalized benzofurans using o-hydroxyphenones and dichloroethylene.

The preparation of highly functionalized benzofurans by a unique and connective transformation is reported. Base-catalyzed condensation of o-hydroxyphenones with 1,1-dichloroethylene generates the corresponding chloromethylene furans. These labile intermediates undergo a facile rearrangement into benzofuran carbaldehydes under mild acidic conditions.

Highly chemoselective reduction of carbonyl groups in the presence of aldehydes.

The exquisite ability of diethylaluminum benzenethiolate to efficiently discriminate between aldehydes and other carbonyl functions enables the chemoselective in situ reduction of ketones and methyl esters in the presence of aldehydes. This potent strategy avoids the usual drawbacks of traditional protecting group methodologies and could be extended to various other transformations.

Unexpected preparation of (Z)-chloromethyleneketals and their sulfur analogues by a novel three-component condensation.

A novel multicomponent condensation, leading to the rare (Z)-chloromethyleneketals and their sulfur analogues, has been discovered. The mechanism of this reaction has been studied in some detail and subsequent modifications were performed on the adducts, leading to unusual Umpolung transforms.

Novel electrochemical deoxygenation reaction using diphenylphosphinates.

The electrochemical reduction of diphenylphosphinate esters leads smoothly and in high yields to the corresponding deoxygenated products. In comparison with the previously developed methodologies, the electrolysis could be performed at lower temperature and with a higher current density, resulting in a shorter reaction time.

IPr* an easily accessible highly hindered N-heterocyclic carbene.

Herein, we wish to describe the efficient three-step synthesis of a novel highly hindered, but flexible, N-heterocyclic carbene and its coordination chemistry to Ag(i) and Rh(i).

Chemoselective chemical and electrochemical deprotections of aromatic esters.

Alcohols can be easily and chemoselectively deprotected from the corresponding aromatic esters by using either SmI(2)/HMPA or by electrolysis in the presence of a proton source.

Unexpected nucleophilic behaviour of free-radicals generated from alpha-iodoketones.

The unexpected nucleophilic reactivity of free-radicals generated from alpha-iodoketones is reported; two different procedures, either employing tin or the more environmentally acceptable ethylsulfone-based coupling reagent have been developed.