Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones, which is particularly useful less accessible acyclic α-tertiary cases. By protonation–amination sequence, our represents rare H–heteroatom bond insertion by α-carbonyl sulfonium ylides, an attractive surrogate diazocarbonyls. The mild intermolecular C–N formation was catalyzed phosphoric acids with excellent efficiency and enantioselectivity. products are precursors to other important amine...

An enantioselective route to the tetracyclic core structure of novel antibiotic lead compound platensimycin is accomplished in 10 steps from simple commercially available starting materials. Highlights this synthesis include (1) a regio- and Diels−Alder reaction between methyl acrylate cyclopentadiene give adduct 2 with essentially complete regio-, diastereo-, enantiocontrol; (2) oxidative decarboxylation ester using nitrosobenzene; (3) one-pot reductive cyanation lactone 4; (4)...

Lewis acid catalyzed inverse-electron-demand Diels−Alder reaction of tropone derivatives was developed. Up to 97% ee obtained for the chiral dinucleus BINOL−aluminum complex between tropones and ketene diethyl acetal give bicyclo[3.2.2] ring structures, which opens up a unique way making seven-membered rings.

A novel transition-metal-free, sulfur mediated allylic C-H alkylation reaction through a one-pot procedure involving an ene-like step between simple olefins and activated sulfoxides to generate sulfonium intermediates, subsequent [2,3]-sigmatropic rearrangement under basic conditions give products, has been developed. This method is applicable tri- disubstituted olefin substrates in both inter- intramolecular fashions.

A green method for simultaneous extraction and enrichment of flavonoids from Euonymus alatus was developed by ultrasonic-assisted (UAE) temperature-induced cloud point (TICPE) using PEG-base aqueous solution as the extractant. Based on screening different molecular weights PEGs, PEG-400/water used extractant, effects key factors yields were investigated single-factor experiments response surface methodology (RSM). The optimum conditions UAE follows: PEG-400 concentration 16% (w/w), particle...

Objective The visual guiding system, as a tunnel traffic safety improvement method by using facilities to actively guide driving safely, has been widely used in countries with many tunnels, recent years. This paper aims quantitatively study the comprehensive evaluation of system which certain engineering application value and can provide support for quantitative optimal design safety.

New nucleophiles for the O-nitroso aldol reaction in form of readily prepared disilanyl enol ethers make this transformation more practical and versatile. A silver catalyst with a chiral biaryl phosphite ligand promotes title high enantio- regioselectivity (see scheme). R1,R2 = H, Ar; TMS trimethylsilyl.

Synthesis of α-heterosubstituted ketones and related heterocyclic structures was achieved through sulfur mediated difunctionalization internal alkynes in one pot.

A sulfur-mediated electrophilic cyclization reaction of aryl-tethered internal alkynes has been developed. Triflic anhydride-activated sulfoxides induced the and then demethylation with triethylamine in one pot, affording 3-sulfenyl-1,2-dihydronaphthalenes related types products yields ≤96%.

This study intends to explore people's satisfaction with sidewalk environments and examine its association emotional perceptions physical components. A perception survey was taken evaluate the of 20 105 participants. Two factors were identified as harmoniousness openness through factor analysis. Then, a path model tested relationship among satisfaction, factors, components environments. The demonstrates good fit data. Furthermore, results show that overall is more strongly directly affected...

A novel organic acid-base-co-catalyzed conversion of styrylepoxides into [1,1'-biaryl]-3-carbaldehydes was realized under microwave irradiation. Styrylepoxides first underwent an acid-catalyzed Meinwald rearrangement followed by a tandem base-catalyzed Michael addition, aldol and aromatization sequence to generate [1,1'-biaryl]-3-carbaldehydes.

Formal synthesis of platencin was achieved by assembling its tricyclic core structure through a Robinson annulation reaction, whose precursor made from bicyclo[3.2.2] ring structure, product tropone Diels–Alder reaction.

In China, serious road traffic crashes (SRTCs) are those in which there 10-30 fatalities, 50-100 injuries, or a total cost of million RMB (U.S.$8-16 M), and particularly (PSRTCs) that more severe costly. Due to the large number fatalities injuries as well negative public reaction they elicit, SRTCs PSRTCs have become great concern China during recent years. The aim this study is identify main factors contributing these propose preventive measures reduce their number.49 occurred from 2007...

<italic>N</italic>-Alkylated 2-pyridone products were obtained in good to excellent yields through a one-pot procedure involving either normal or interrupted Pummerer reactions between triflic anhydride activated sulfoxides and 2-fluoropyridine derivatives, followed by hydrolysis.

Sulfur mediated propargylic C–H alkylation was realized through a one-pot procedure with modest yields and substrate scope. Hopefully, the community could find better solution to this challenge by some novel metal-catalyzed reactions.

Cationic rearrangement reactions usually follow Markovnikov's rule to give more substituted carbocations as stable intermediates. During our study on sulfur mediated allylic C-H amination of olefins, very rare cases anti-Markovnikov from secondary toward primary or triflates were observed.

The silica gel absorbed amino acid salt catalyzed asymmetric intramolecular Robinson annulation reaction has been developed; up to 97% ee was obtained with this readily recoverable organocatalyst.

Abstract This Account discusses several new reaction methods developed in our group that utilize sulfur-mediated reactions through sulfonium salts and ylides, highlighting the interplay of rational design serendipity. Our initial goal was to convert aliphatic C–H bonds into C–C site-selectively, without use transition-metal catalysts. While a proof-of-concept has been achieved, this target is far from being ideally realized. The unexpected discovery an anti-Markovnikov rearrangement...

Nucleophilic organic base DABCO (1,4-diazabicyclo[2.2.2]octane)-mediated Meinwald rearrangement of various epoxides was investigated. 2-Aryl-, alkenyl-, and alkynylepoxides generate the corresponding methyl ketones chemospecifically in good to excellent yields. The current DABCO-mediated features readily accessible starting materials, a wide substrate scope, transition-metal- acid-free environment, chemospecificity isomerization epoxides.