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A visible‐light‐induced selenocyclization of ortho‐vinylanilides to 4H‐3,1‐benzoxazines has been developed under controlled O2 atmosphere. The low O2 content in reaction medium promotes the aerobic selenol oxidation to diselenides for the full use of 2 equiv. selenyl radicals in a redox‐neutral way, avoiding the aerobic oxidation of ortho‐vinylanilides under higher O2 content. The developed visible light‐induced selenocyclization of ortho‐vinylanilides utilizes only visible light with low O2 content, eliminating the use of exogenous photocatalyst and chemical oxidant. [ABSTRACT FROM AUTHOR]

Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper‐containing amine oxidase (CuAO)‐like o‐NQ‐catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)‐like TBHP‐mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP‐mediated oxidation pathways of imines. The developed metal‐free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application. [ABSTRACT FROM AUTHOR]

Divergent halogenation pathways of 2,2‐dichlorobut‐3‐yn‐1‐ols have been developed to give 3,4‐dihalofurans and 1,3‐dihaloallenyl ketones in good to excellent yields. Thus, the readily accessible 2,2‐dichlorobut‐3‐yn‐1‐ols were treated with the electrophilic halogen source to provide the 1,3‐dihalogen‐substituted allenyl ketones, whereas the use of Pd(II) catalyst promoted the oxypalladation followed by the electrophilic halogenation to give 3,4‐dihalogen‐substituted furan derivatives. The synthetic utility of 3,4‐dihalofurans and 1,3‐dihaloallenyl ketones is demonstrated in the sequential Suzuki cross coupling strategies. [ABSTRACT FROM AUTHOR]

Divergent reaction pathways of β‐chlorovinyl ketones have been established to provide stereodefined alkylidenecyclopent‐2‐enones and 2‐alkenylfuran derivatives. The switch of the reaction pathways was made possible by the microwave‐assisted thermal Nazarov cyclization reaction of β‐chlorovinyl ketones, whereas the soft α‐vinyl enolization of β‐chlorovinyl ketones allowed the generation of allenyl ketone intermediates that in turn smoothly underwent cycloisomerization to the 2‐alkenyl furan derivatives in good to excellent yields. [ABSTRACT FROM AUTHOR]

The dehydrogenative coupling of amines by copper catalysts was investigated in the presence of molecular oxygen. By modulating the aerobic oxidation pathways of Cu(OAc)2 catalyst in different reaction solvents, the selective formations of homo‐coupled imines, cross‐coupled imines, and nitriles have been achieved from amine derivatives. The discovery of the multiple aerobic oxidation pathways of Cu(OAc)2 signifies the on demand reactivity control of the catalytically active copper species by the reaction solvents. Given that the aerobic oxidation protocols are of significant interest to the advancement of green chemical processes, the copper‐catalyzed aerobic oxidation reactions will be useful for a wide range of functional group transformations. [ABSTRACT FROM AUTHOR]

Many combustion systems use the technique called exhaust gas recirculation. Thus, the effects of N2/CO2 dilution on the combustion characteristics have been of interest. In this study, the dilution effects on the flame propagation velocity (FPV) of an oxy-methane premixed mixture were investigated using a state-of-the-art annular stepwise diverging tube. The relationship between FPV and the length scale was measured for various equivalence ratios in the dilution ratio range 65–75% N2 and 50–65% CO2. The characteristic variations of FPV in each dilution case could be described as a surface in a concentration–length–velocity diagram, and this provides a bird's eye view of the dilution effects on flame propagation. Two distinctive scalar values of the quenching distance and the critical FPV were investigated. At the same dilution ratio, CO2 dilution caused more significant variation than N2 dilution did regarding FPV, quenching distance, and flammable limits. In particular, the critical FPV was compared with the laminar burning velocity (LBV) calculated using a PREMIX code employing GRI-3.0. In addition, fictitious species (F-N2/F-CO2) were used in the reaction mechanism to distinguish chemical effects. Conclusively, results showed that CO2 dilution reduced LBV significantly not only by its larger thermal capacity but also by its active involvement in the chemical reaction. [ABSTRACT FROM AUTHOR]

The direct regioselective synthesis of highly functionalized pyrroles with two different electron-withdrawing groups has been developed using an angle strain-induced 1,2-shift of an electron-withdrawing group in 2 H-pyrroles. The preferential migration aptitude of an electron-withdrawing group over alkyl and aryl groups is believed to be the result of the orbital overlap between the internal alkene and the electron-withdrawing group. The newly developed regioselective synthesis of pyrroles features a wide substrate scope, simple reaction set-up, and high yields (60-82%), capturing the essence of alkyne-isocyanide 'click' reactions. [ABSTRACT FROM AUTHOR]

Enantiodivergent catalyst systems were developed using metals with different ionic radii and a multifunctional brucine diol (BD) ligand. The catalytic use of purported 1:1 Cu-BD complexes in the 1,3-dipolar cycloaddition of azomethine ylides with chalcones resulted in the selective formation of endo-pyrrolidines in 87-96% ees with an absolute stereochemical outcome of (2 R,3 S,4 R,5 S). In contrast, an opposite absolute stereochemical outcome was observed by using the catalysts derived from Ag(I) salts and BD. The demonstration of enantiodivergent approaches to a broad class of substrates/reaction types underlines their synthetic value in asymmetric synthesis. [ABSTRACT FROM AUTHOR]

Kumulierte Zwischenstufe: Die milde Vinylenolisierung von (E) ‐ β ‐ Chlorvinylketonen ermöglicht die In ‐ situ ‐ Bildung von elektrophilen Lithium[3]cumulenolaten, die mit Nucleophilen wie z. B. einem weiteren Lithium[3]cumulenolat stereoselektiv zu Vinylallenonen reagieren. Sie können auch mit Ketiminestern zu 3 ‐ Methylenpyrrolidinen umgesetzt werden. [ABSTRACT FROM AUTHOR]

Soft spot: The soft vinyl enolization of (E)‐β‐chlorovinyl ketones results in the in situ generation of electrophilic lithium [3]cumulenolates, which react with nucleophiles such as another lithium [3]cumulenolate to stereoselectively form vinyl allenones. They can also react with ketimine esters to give 3‐methylenepyrrolidines. [ABSTRACT FROM AUTHOR]

α ‐ Acylvinylanion ‐ Synthone wurden durch direkte α ‐ Vinyl ‐ Enolisierung α,β ‐ ungesättigter Ketone unter milden Reaktionsbedingungen zugänglich. Der präparative Nutzen solcher Synthone wurde anhand intermolekularer Aldol ‐ und Aldolkondensationsreaktionen gezeigt, die nützliche Allenylketon ‐ und Eninderivate liefern. [ABSTRACT FROM AUTHOR]

Synthesizing the synthons: The development of α‐acylvinyl anion synthons has been achieved using direct α‐vinyl enolization of α,β‐unsaturated ketones under mild reaction conditions. The synthetic utility of such synthons has been demonstrated in intermolecular aldol and aldol condensation reactions, which provide synthetically useful allenyl ketone and enyne derivatives. [ABSTRACT FROM AUTHOR]

The prevalence of cyclopropanes in biologically active compounds has fueled many investigations into their preparation. Despite significant advances, more efficient methods for their catalytic enantioselective synthesis remain in demand. Previously, we reported a novel tandem approach to diastereo- and enantioenriched cyclopropyl alcohols. Our method involved an initial asymmetric C-C bond formation by addition of organozinc reagents to aldehydes catalyzed by a (−)-MIB-based catalyst. The resulting allylic zinc alkoxides were then subject to directed cyclopropanations. Although this approach provided cyclopropyl alcohols with very high enantio- and diastereoselectivity, it was successful with only aliphatic aldehydes. Aryl aldehyde substrates, on the other hand, exhibited low conversion and variable diastereomeric ratios. The present study is aimed at raising the stereoselectivity and yield of the aforementioned tandem reaction with aryl aldehyde substrates to make the method synthetically useful. Herein, we report the successful optimization of aryl aldehyde substrates in our one-pot tandem approach leading to cyclopropyl alcohols with high yields and enantio- and diastereoselectivities. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The on-board tilting mirror calibration mechanism has a mechanical driving part that helps to achieve the main functional modes of deployment and stow when calibrating a spaceborne imaging sensor. In general, it is necessary to consider a holding and release device in the mechanism design, to secure the structural safety of the mechanical driving part in severe launch environments. However, in the present study, we proposed a novel design strategy based on mass balancing, to guarantee mechanical safety on the driving part of the tilt mirror mechanism, although the implementation of the holding and release mechanism was not considered in the design. The effectiveness of the proposed design was experimentally verified via launch vibration and life cycle tests. The test results demonstrated that the mechanism fulfills all the required functions, and the design approach proposed in this study is effective for ensuring mechanical safety on the driving part of the tilting mirror mechanism in severe launch vibration environments. [ABSTRACT FROM AUTHOR]

Cover Feature: Copper(II)-Catalyzed Aerobic Oxidation of Amines: Divergent Reaction Pathways by Solvent Control to Imines and Nitriles (Asian J. Org. The catalytic use of Cu(OAc) SB 2 sb under molecular oxygen promoted the oxidation of amines to either imines or nitriles by simply changing the reaction solvent. Aerobic oxidation, amines, copper catalyst, imines, nitriles. [Extracted from the article]