BF3·OEt2-mediated transamidation of unprotected primary amides under solvent-free conditions.

A BF3·OEt2-mediated transamidation between unactivated amides and amines is reported, enabling access to diverse secondary and tertiary amides under transition-metal-free and solvent-free conditions. The operationally simple procedure provides a novel manifold for converting amide-amide bonds with excellent chemoselectivity. In particular, a series of amides including challenging thioamides enable direct transamidation to products with modest to excellent yields. Meanwhile, additional experiments were conducted to elucidate the mechanism of this transformation, and a plausible mechanism was proposed based on the results and related literature.

Proposal for the classification of sinomenine alkaloids.

The chemical structure of sinoacutine is formed by a phenanthrene nucleus and an ethylamine bridge. Because it has a similar parent structure to morphine, it is subdivided into morphinane. At present, all reports have pointed out that the basic skeleton of morphine alkaloids is salutaridine (the isomer of sinoacutine), which is generated by the phenol coupling reaction of (R)-reticuline. This study shows that the biosynthetic precursors of sinoacutine and salutaridine are different. In this paper, the sinoacutine synthetase (SinSyn) gene was cloned from Sinomenium acutum and expressed SinSyn protein. Sinoacutine was produced by SinSyn catalyzed (S)-reticuline, according to the results of enzyme-catalyzed experiments. The optical activity, nuclear magnetic resonance, and mass spectrum of sinoacutine and salutaridine were analyzed. The classification and pharmacological action of isoquinoline alkaloids were discussed. It was suggested that sinoacutine should be separated from morphinane and classified as sinomenine alkaloids.

S-alkyl Dithiocarbamates Synthesis through Electrochemical Multicomponent Reaction of Thiols, Hydrogen Sulfide, and Isocyanides.

Dithiocarbamates synthesis is extremely important in plenty of biomedical and agrochemical applications, especially fungicide development, but remains a great challenge. In this work, we have successfully developed a multicomponent reaction protocol to convert H2S into S-alkyl dithiocarbamates under constant current conditions. No additional oxidants nor additional catalysts are required, and due to mild conditions, the reactions display a broad substrate scope, including varieties of thiols or disulfides.

A peptide aptamer based electrochemical amperometric sensor for sensitive L-glutamate detection.

L-glutamate (L-Glu) has gained much attention owing to its contribution to the umami taste and it plays important roles in the central nervous system. Herein, an enzyme-free amperometric biosensor based on a peptide possessing an electroactive ferrocene linker as ferrocene-Gly-Gly-Gly-Gly-Ile- Pro-Val-Tyr-Cys-Gly-Leu-Ile-Gly-Gly-Gly-Gly-Lys-(CH2)4- thioctic acid self- assembled on gold electrode was designed and fabricated for specific determination of L-Glu. The biosensor was characterised via cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and scanning electron microscopy. The biosensor showed optimum response within 200 s at 0.10 V in phosphate-buffered saline. Moreover, the biosensor exhibited excellent sensitivity and a low detection limit of 1.00 × 10-10 M. The sensitivity at an L-Glu concentration of 1.00 × 10-7 M - 1.00 × 10-3 M was 0.1572 µA/M, and that at an L-Glu concentration of 1.00 × 10-10 M - 1.00 × 10-7 M was 0.0293 µA/M. The peptide-based biosensor had excellent specificity and a wider linear range. The relative standard deviation of the L-Glu concentrations measured by the biosensor in a hundred-fold dilution of mouse serum samples was less than 5.00% compared with the high-performance liquid chromatography results, and the recovery rate of L-Glu was from 93.32% to 105.15%.

Visible-Light Photosynthesis of CHF2 /CClF2 /CBrF2 -Substituted Ring-fused Quinazolinones in Dimethyl Carbonate.

With eco-friendly and sustainable CO2 -derived dimethyl carbonate as the sole solvent, the visible-light-induced cascade radical reactions have been established as a green and efficient tool for constructing various CHF2 /CClF2 /CBrF2 -substituted ring-fused quinazolinones.

Electrosynthesis of S-thiocarbamates with disulfides as a sulfur source.

An electrochemical oxidative synthesis of S-thiocarbamates by a carbamothioation reaction via a three-component coupling reaction (disulfide, water and isocyanide) is developed, which avoids the use of external oxidants and generates only hydrogen gas as the by-product. With NH4I as the mediator and electrolyte, the desired S-thiocarbamates were obtained in good yields in an undivided cell at room temperature.

Ultrasound-assisted bromination of indazoles at the C3 position with dibromohydantoin.

Bromoaryl compounds have attracted great attention in organic chemistry, especially for the synthesis of pharmaceutical intermediates. Herein, we demonstrated a novel and efficient bromination protocol of indazoles via C-H bond cleavage to give site-specific 3-bromide products that could be further employed as synthetic blocks to prepare drugs. The reaction used DBDMH as a bromine source, tolerated a wide range of indazoles, and finished in 30 min under mild, ultrasound-assisted conditions. Besides, preliminary mechanistic studies revealed that this approach was not a radical process.

Ultrasound-Assisted Iodination of Imidazo[1,2-α]pyridines Via C-H Functionalization Mediated by tert-Butyl Hydroperoxide.

A novel metal catalyst-free and environmentally friendly method for the regioselective iodination of imidazo[1,2-α]pyridines at their C3 position is disclosed, which has a wide substrate scope and could be sustainable. This reaction proceeds through ultrasound acceleration in the presence of a green alcohol solvent. Compared with a conventional heating system, the reaction efficiency and the rate are significantly improved and the iodine atom economy is maximized using ultrasound techniques.

Diethylaminosulfur Trifluoride: A Novel, Low-Cost, Stable Double Thiolation Reagent for Imidazo[1,2-α]pyridines.

We report a novel, inexpensive double thiolation reagent that sulfurizes a broad range of imidazo[1,2-α]pyridines under mild conditions. Importantly, diethylaminosulfur trifluoride, as a common nucleophilic fluorinating reagent, was utilized as a novel thiolation reagent.

Photoinduced efficient synthesis of cyanoalkylsulfonylated oxindoles via sulfur dioxide insertion.

A visible-light-promoted radical cascade reaction of N-arylacrylamide and cyclobutanone oxime esters with sulfur dioxide insertion is established. Mainly through the exploration of the visible light wavelength, it is found that the light source has a certain influence on the formation of cyanoalkylsulfonylated oxindoles, furnishing a range of sulfones in good to excellent yields. This protocol presents good functional group compatibility and does not require transition metals, photosensitizers, external bases, or oxidants.

Electrochemically promoted oxidative α-cyanation of tertiary and secondary amines using cheap AIBN.

The electrochemical α-cyanation of tertiary and secondary amines has been developed by using a cheap cyanide reagent, azobisisobutyronitrile (AIBN). The CN radical, generated through n-Bu4NBr-meidated electrochemical oxidation, participates in a novel α-cyanation reaction under exogenous oxidant-free conditions.

An antifouling polymer for dynamic anti-protein adhesion analysis by a quartz crystal microbalance.

Nowadays, the non-specific adsorption of biomolecules is a key issue in numerous fields. Herein, an improved antifouling molecule was synthesized by grafting phenol with oligopoly (ethylene glycol), named (4-(2-(2-ethoxyethoxy) ethoxy) phenol (EEP). An ideal antifouling polymer coating (PEEP) was synthesized by the mechanism of electropolymerization of phenol. Quartz crystal microbalance (QCM), a sensitive mass sensor, was used to dynamically monitor both the modification and anti-protein adhesion (with bovine serum albumin as the model) process. Quantitatively, less proteins were observed to adhere to the modified electrode (277.8 ng for bare GCE and 8.88 ng for the modified GCE). Fourier transform infrared spectrophotometry (FT-IR), scanning electron microscopy (SEM), and electrochemical methods were used to study the coatings in detail. In this study, EEP was synthesized for the electrochemical preparation of an antifouling coating and characterized by QCM and electrochemical methods. The mild preparation environment (lower potential window and in phosphate buffered saline) and one-step method enable potential applications of PEEP in the field of biomaterials and biosensors.

Copper(i)-catalyzed intermolecular cyanoarylation of alkenes: convenient access to α-alkylated arylacetonitriles.

A novel Cu(i)-catalyzed intermolecular cyanoarylation of alkenes with diaryliodonium salts as a radical arylating reagent and tetra-butylammonium cyanide as an electrophilic cyanating reagent was established. A broad range of α-alkylated arylacetonitriles were efficiently constructed in good to excellent yields under base- and oxidant-free and mild conditions.

Electrochemical Synthesis of α-Ketoamides under Catalyst-, Oxidant-, and Electrolyte-Free Conditions.

A catalyst-, oxidant-, electrolyte-free method for the preparation of α-ketoamides through the direct electrochemical amidation of α-ketoaldehydes and amines with innocuous hydrogen as the sole byproduct at ambient temperature was developed. The present reaction features clean and mild conditions, excellent functional-group tolerance, and high atom economy and scalability, enabling facile applications in pharmaceutical chemistry.

Ultrasound accelerated synthesis of O-alkylated hydroximides under solvent- and metal-free conditions.

A novel, sustainable, environmentally friendly, high substrate scope, efficient, solvent-free and metal catalyst-free method for the cross-dehydrogenative coupling (CDC) reaction between N-hydroxyphthalimide (NHPI) and benzyl/ether compounds is described. This coupling reaction proceeds through ultrasound acceleration. Compared to conventional heating conditions, the use of ultrasound techniques not only improves the reaction efficiency and enhances the reaction rate but also minimizes the side reactions.

Copper-catalyzed desymmetrization of prochiral 4,4-disubstituted cyclopentenes via a site-selective allylic oxidation: a concise total synthesis of untenone A.

The desymmetrization of prochiral 4,4-disubstituted cyclopentenes via a site-selective copper-catalyzed allylic oxidation is described. This study provides a direct comparison of a series of known methods for allylic oxidation, and thus identifies ligand-free copper(i) iodide as the optimal catalyst for this particular process. Notably, this work offers a convenient approach to the preparation of γ-quaternary α,ß-unsaturated cyclopentenones, which permits an efficient three-step total synthesis of (±)-untenone A.

TBAI-catalyzed selective synthesis of sulfonamides and ß-aryl sulfonyl enamines: coupling of arenesulfonyl chlorides and sodium sulfinates with tert-amines.

A simple, practical and metal-free method has been developed for the synthesis of sulfonamides and ß-arylsulfonyl enamines via the selective cleavage of C-N and C-H bonds through the iodine-catalyzed oxidation of arenesulfonyl chlorides and sodium sulfinates with tert-amines. The method uses commercially available inexpensive catalysts and oxidants, and has a wide substrate scope and operational simplicity.

E-Selective synthesis of vinyl sulfones via silver-catalyzed sulfonylation of styrenes.

An efficient and highly E-selective protocol for the synthesis of vinyl sulfones is described. This simple protocol demonstrates the first synthesis of vinyl sulfones via a silver-catalyzed C-S bond coupling reaction. In addition, the success of the reaction was found to be critically dependent on the use of TEMPO as the additive.

Synthesis of Aryl Alkynes via Copper Catalyzed Decarboxylative Alkynylation of 2-Nitrobenzoic Acids.

An efficient protocol for the synthesis of internal aryl alkynes was achieved via Cu-catalyzed decarboxylative cross-coupling reactions, and to the best of our knowledge, this is the first example of a Cu-catalyzed decarboxylative alkynylation of benzoic acids with terminal alkynes. This approach utilizes simple Cu salt as catalyst and O2, an abundant, clean, and green material, as the oxidant. The reaction tolerates various functional groups, and a variety of internal aryl alkynes were synthesized in 46-83% yields.

Selective Synthesis of Aryl Nitriles and 3-Imino-1-oxoisoindolines via Nickel-Promoted C(sp2)-H Cyanations.

An efficient nickel-promoted selective monocyanation of benzamides with TMSCN via 8-aminoquinoline directed ortho C-H activation has been developed. Varieties of functionalized ortho-cyanated (hetero)aryl nitriles can be selectively synthesized in moderate to good yields. These cyanation products can be easily transformed into various 3-imino-1-oxoisoindolines in a one-pot procedure. The mild reaction conditions, use of cheap and commercially available reagents, wide functional group tolerance, and operational convenience make this protocol practical to the synthetic community.