N-Heterocyclic Carbene Catalyzed [4+2] Annulation of Enals via a Double Vinylogous Michael Addition: Asymmetric Synthesis of 3,5-Diaryl Cyclohexenones
A strategy for the N-heterocyclic carbene (NHC) catalyzed asymmetric synthesis of 3,5-diaryl substituted cyclohexenones has been developed via oxidative [4+2] annulation of enals and alkenylisoxazoles. It is the first example of using NHC organocatalysis in a double vinylogous Michael type reaction, a challenging but highly desirable topic. This unprecedented protocol affords good yields as well as high to excellent diastereo- and enantioselectivities.
N-heterocyclic carbene organocatalysis allows the [4+2] annulation of enals with electron-deficient 2,4-dienes via a double vinylogous Michael addition sequence. The corresponding 3,5-diaryl cyclohexenones are obtained in good to excellent yields with high to excellent diastereo- and enantioselectivities.
With spring in the air and one’s thoughts naturally turning to those of romantic rendezvous, police in Lethbridge kindly ask they not take place in city greenspaces.
Complaints of couples engaging in sexual acts along the Old Man river valley have reached what police are calling chronic levels, prompting officials to increase patrols in the greenspaces surrounding the Elks Compound near Fort Whoop-Up.
City crews are also engaged in removing trees and cutting brush in an attempt to deter the activity, which often takes place in full view of both park visitors and the police.
Couples caught in coitus have so far been issued warnings by officers, but police warn criminal charges may be laid if the outdoor dalliances continue.
Anybody who observes lewd conduct in any public place is asked to call Lethbridge police at 403-328-4444.
Since Four will have a limited role to play in this story (on account of being comatose due to poison), I thought I’d at least let her be a pain in the ass at the table.
– Break the binge: How to turn off autoplay for the next episode on Netflix. (via)
– Feminist pin.
– Fire Drills: Communications Strategy in a Crisis
– My kind of gun.
– Really cute Kids Travel Blankets.
– “Both the military and professional kitchens are environments where there’s zero tolerance for slackers and indecision” – Why Chefs and Soldiers Make the Best Product Managers
– This is a smart coat for airplane travel.
– This tray!
– Want to convince someone to help you with a project? Try the bingo method.
– Some of these signs made me laugh out loud.
– I heard this book helps you teach your kids about money. I’ll order it and will see for myself.
– Here’s something to try at home: 6 fun activities to introduce your kids to physics!
– Made me laugh: IKEA “Relationship Saving Station”
Just three-ish days left in the Dumbing of Age Book 6 Kickstarter, and here’s Sal, the final, thirteenth magnet for the Kickstarter!
Remember, there are PICK THREE MAGNETS and now PICK FIVE MAGNETS pledge tiers, where you can choose which three or five magnets you want, PLUS the bonus Becky magnet everyone (with a real paper book) gets. So if you want a Sal, there’s a good chance there’s a way to add her.
In Situ Construction of Stable Tissue-Directed/Reinforced Bifunctional Separator/Protection Film on Lithium Anode for Lithium–Oxygen Batteries
To achieve a high reversibility and long cycle life for Li–O2 battery system, the stable tissue-directed/reinforced bifunctional separator/protection film (TBF) is in situ fabricated on the surface of metallic lithium anode. It is shown that a Li–O2 cell composed of the TBF-modified lithium anodes exhibits an excellent anodic reversibility (300 cycles) and effectively improved cathodic long lifetime (106 cycles). The improvement is attributed to the ability of the TBF, which has chemical, electrochemical, and mechanical stability, to effectively prevent direct contact between the surface of the lithium anode and the highly reactive reduced oxygen species (Li2O2 or its intermediate LiO2) in cell. It is believed that the protection strategy describes here can be easily extended to other next-generation high energy density batteries using metal as anode including Li–S and Na–O2 batteries.
The stable tissue-directed/reinforced bifunctional separator/protection film (TBF) is in situ fabricated on the surface of metallic lithium anode. The Li–O2 battery cell with the TBF-modified lithium anodes exhibits an excellent anodic reversibility and effectively improved cathodic long lifetime.
When you find a bit of mold on food, it might seem like it’s okay to salvage some of it because the mold doesn’t cover the whole thing. That seems like the logical step, right? It turns out that’s not true for a lot of foods, like bread, because the mold can hide deep in the surface where you can’t see it.
A general palladium-catalyzed synthesis of linear esters directly from sec- and tert-alcohols is described. Compared to the classic Koch–Haaf reaction, which leads to branched products, this new transformation gives the corresponding linear esters in high yields and selectivity. Key for this protocol is the use of an advanced palladium catalyst system with L2 (pytbpx) as the ligand. A variety of aliphatic and benzylic alcohols can be directly used and the catalyst efficiency for the benchmark reaction is outstanding (turnover number up to 89 000).
Ligands with built-in function make possible the first general carbonylation of tert- and sec-alcohols to give the linear esters. The reactions complement the classic Koch–Haaf carbonylation. A variety of aliphatic and benzylic alcohols can be directly used.
Tuning Energy Levels without Negatively Affecting Morphology: A Promising Approach to Achieving Optimal Energetic Match and Efficient Nonfullerene Polymer Solar Cells
One advantage of nonfullerene polymer solar cells (PSCs) is that they can yield high open-circuit voltage (VOC) despite their relatively low optical bandgaps. To maximize the VOC of PSCs, it is important to fine-tune the energy level offset between the donor and acceptor materials, but in a way not negatively affecting the morphology of the donor:acceptor (D:A) blends. Here, an effective material design rationale based on a family of D–A1–D–A2 terthiophene (T3) donor polymers is reported, which allows for the effective tuning of energy levels but without any negative impacts on the morphology of the blend. Based on a T3 donor unit combined with difluorobenzothiadiazole (ffBT) and difluorobenzoxadiazole (ffBX) acceptor units, three donor polymers are developed with highly similar morphological properties. This is particularly surprising considering that the corresponding quaterthiophene polymers based on ffBT and ffBX exhibit dramatic differences in their solubility and morphological properties. With the fine-tuning of energy levels, the T3 polymers yield nonfullerene PSCs with a high efficiency of 9.0% for one case and with a remarkably low energy loss (0.53 V) for another polymer. This work will facilitate the development of efficient nonfullerene PSCs with optimal energy levels and favorable morphology properties.
A terthiophene-based donor polymer PffBTBX-T3 with the D–A1–D–A2 structure is demonstrated and compared with the other two D–A-type polymers PffBT-T3 and PffBX-T3. While the energy levels of three polymers are fine-tuned, their optical and morphological properties are not dramatically changed. The optimal energetic match and well-controlled morphology enable 9.0% efficient nonfullerene devices based on PffBTBX-T3 and ITIC-Th.
Layered Double Hydroxide Nanosheets with Multiple Vacancies Obtained by Dry Exfoliation as Highly Efficient Oxygen Evolution Electrocatalysts
Layered double hydroxides (LDHs) with two-dimensional lamellar structures show excellent electrocatalytic properties. However, the catalytic activity of LDHs needs to be further improved as the large lateral size and thickness of the bulk material limit the number of exposed active sites. However, the development of efficient strategies to exfoliate bulk LDHs into stable monolayer LDH nanosheets with more exposed active sites is very challenging. On the other hand, the intrinsic activity of monolayer LDH nanosheets can be tuned by surface engineering. Herein, we have exfoliated bulk CoFe LDHs into ultrathin LDH nanosheets through Ar plasma etching, which also resulted in the formation of multiple vacancies (including O, Co, and Fe vacancies) in the ultrathin 2D nanosheets. Owing to their ultrathin 2D structure, the LDH nanosheets expose a greater number of active sites, and the multiple vacancies significantly improve the intrinsic activity in the oxygen evolution reaction (OER).
Thinner and thinner: The dry exfoliation of bulk CoFe layered double hydroxides into ultrathin nanosheets with multiple vacancies was achieved by argon plasma etching to disrupt the intrinsic interlayer electrostatic interactions. These nanosheets are superior electrocatalysts for the oxygen evolution reaction.
User interface design is hard, but we’ve been getting better at it over the years to the point where even a thermostat is easy to use. Automakers, however, seem to have their heads in the sand, taking their design inspiration for their infotainment consoles from old Winamp skins instead of any type of modern interface.
Enantioselective Silver and Amine Co-catalyzed Desymmetrizing Cycloisomerization of Alkyne-linked Cyclohexanones
A silver(I) and amine co-catalyzed desymmetrization of 4-propargylamino cyclohexanones for the direct enantioselective synthesis of 2-azabicyclo[3.3.1]nonanes is described. Exploiting reactivity arising from dual activation of the pendant terminal alkyne by silver(I) and the ketone moiety through transient enamine formation, this synthetically relevant transformation is easy to perform, efficient and broad in scope. High enantioselectivity (up to 96 % ee) was achieved by exploiting a significant matching effect between the chirality of a cinchona alkaloid-derived aminophosphine ligand for the silver(I) salt and the 2-bis(aryl)methylpyrrolidine catalyst which was rationalized by DFT calculations. This allowed for the preparation of both enantiomers of the bicyclic product with near-identical stereocontrol.
A matching effect between a chiral aminocatalyst and a chiral ligand for silver is exploited in the title reaction of 4-propargylamino cyclohexanones for the direct enantioselective synthesis of 2-azabicyclo[3.3.1]nonanes. The reaction is efficient, broad in scope and proceeds with high enantioselectivity.
Base-Controlled Completely Selective Linear or Branched Rhodium(I)-Catalyzed C−H ortho-Alkylation of Azines without Preactivation
A [RhI]/bisphosphine/base catalytic system for the ortho-selective C−H alkylation of azines by acrylates and acrylamides is reported. This catalytic system features an unprecedented complete linear or branched selectivity that is solely dependent on the catalytic base that is used. Complete branched selectivity is even achieved for ethyl methacrylate, which enables the introduction of a quaternary carbon center. Excellent functional group compatibility is demonstrated for both linear and branched alkylations. The operational simplicity and broad scope of this transformation allow for rapid access to functionalized azines of direct pharmaceutical and agrochemical relevance.
A basic choice: The linear/branched selectivity of an ortho-selective C−H alkylation of azines without preactivation is completely controlled by a simple switch between base catalysts. Under the “branched” conditions even quaternary carbon centers can be introduced. Excellent functional group compatibility is demonstrated for both linear and branched alkylations with acrylate derivatives.