A dynamic nucleophilic aromatic substitution of tetrazines (SNTz) is presented herein. It combines all the advantages of dynamic covalent chemistry with the versatility of the tetrazine moiety. Indeed, libraries of compounds or sophisticated molecular structures can be easily obtained, which are susceptible to post-functionalization by Inverse Electron Demand Diels-Alder (IEDDA) reaction, which also locks the exchange. Additionally, the structures obtained can be disassembled upon the application of the right stimulus, either UV-irradiation or a suitable chemical reagent. Moreover, SNTz is compatible with the imine chemistry of anilines. The high potential of this methodology has been proved by building two responsive supramolecular systems: A macrocycle that displays a light-induced release of acetylcholine; and a truncated [4+6] tetrahedral shape-persistent fluorescent cage which is disassembled by thiols unless it is post-stabilized by IEDDA.
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Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c00307
Thijs Stuyver and Sason Shaik
https://ift.tt/38lN0ic
I am trying to do phenanthroline nucleophilic aromatic substitution with bromomesitylene in both 2, 9 positions but I face many frustrating problems still cannot be solved by myself. First I performed the usual halogen-lithium exchange by mixing n-BuLi and bromomesitylene first for about an hour then added 1,10-phenanthroline, and all I got were n-butyl- or mestyl-monosubstituted products, monosubstituted product is okay because next I can perform the second substitution, but the yield is bad (< 40%) with comparable n-butyl monosubstituted product. I have read some papers also worked on mesityl-substituted phenanthroline and they got the yield with 60-80%, with little butyl one, and I still cannot figure out why...and I dried everything THOROUGHLY before the reaction!
Alternatively, I also used metal lithium to perform the same reaction, and although the lithium in our lab already has some white covering, putting it into water was still bubbling violently, so I used it. But I failed again and again. After added phenanthroline to the Li and bromomesitylene mixture the solution didn't turn the characteristic dark color, so I think the problem might be the mesityllithium didn't even be produced? Also a paper mentioned that using ''old'' bromomesitylene would cause the production of mesityllithium dropping from 100% to 40%, and I don't know whether this is another problem, but the 1H NMR spectrum of bromomesitylene I used is perfectly matched!!...
Desperately , I tried another synthetic pathway that is to couple the mesityl boronic acid with 2,9-dichloro-1,10-phenanthroline, and this time I face the problems to synthesize the dichlorophenanthroline. All the reaction conditions I found were simply mixing the precursor propano-bridged phenanthroline dione with 2 eq. PCl5 and POCl3 as solvent and refluxed for 8 to 16 hours, with good yield (~ 80 to almost 100%). Before refluxing I also degassed the mixture but the crude I got was totally a mess, sometimes even with some starting material unreacted. The POCl3 in our lab was purchased >10 years ago and PCl5 was about 2.5 years ago.
Sorry for the bad English but I am so frustrated that hope I can get some help from here, thank you.
https://preview.redd.it/knc3tnzdm4961.jpg?width=853&format=pjpg&auto=webp&s=dd4c393744a17f77b1e08b13ae2d1c1a6889a519
Non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr). Remarkably, both electron‐neutral and electron‐rich aryl fluorides participated in the reaction with substantially stabilized anionic P‐nucleophiles to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism, which involves both concerted and stepwise SNAr reaction pathways.
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Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c12619
Toshiya Ikeuchi, Keiichi Hirano, and Masanobu Uchiyama
https://ift.tt/3c3sEvf
Which will be more reactive to an NAS reaction?
The things that come to my mind are steric effects and hyperconjugation.
When the pi electrons transfer onto the oxygen after the carbon is attacked by the nucleophile, the carbocation will be stabilized by hyperconjugation, but will a carbon bonded to 2H 1C be more effective or 2C 1H?
An steric effects obviously makes me lean more towards the left molecule.
https://preview.redd.it/bbtdusnvcrs61.jpg?width=3536&format=pjpg&auto=webp&s=e5c5ca82377191b5201bbe7a622611c58ede5c36
Why does the following reaction occur? The pKa of HCl is higher than that of HI. Therefore I- is a better leaving group. Although Cl-is a weak nucleophile, I- is a better leaving group. Therefore, what stops the Cl- from attacking the product, causing I- to be the leaving group again?
https://preview.redd.it/tuukgp5cbua61.png?width=624&format=png&auto=webp&s=f5b4128afb4fda6944099f308807ee101f72e394
I have a textbook which appears to contradict itself.
In one instance: a nucleophilic substitution requires aqueous solvent at room temperature.
In another instance: a nucleophilic substitution reaction requires ethanolic solvent at hot temperature.
If someone could clear this up for me I’d be greatly appreciative.
Nature Chemistry, Published online: 11 January 2021; doi:10.1038/s41557-020-00609-7
A wide variety of bioactive molecules contain stereogenic quaternary carbons, and developing methods for the construction of these stereocentres continues to be an active area of research. Now, it has been shown that a nickel-catalysed enantioconvergent coupling of tertiary alkyl electrophiles with alkenylmetal nucleophiles—which probably proceeds via a radical pathway—can form and set quaternary stereocentres efficiently under mild conditions.
https://ift.tt/3i4YJp5
Just trying to reinforce my concepts and I was looking over a question related to this. Does peptide bond formation occur through this mechanism? We're replacing the -OH of the carboxyl group an amine group effectively (amide bond formation).
I recently performed a lab where we brominated Veratrole, apparently bromination occurs at only positions 4 and 5. I find this confusing as when I draw out the resonance structures (I drew here: https://imgur.com/a/HxNpUOA) it seems to me that the bromine could be added just about any position. Could someone please offer insight to why this is?
Exactly what the title says.
Non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr). Remarkably, both electron‐neutral and electron‐rich aryl fluorides participated in the reaction with substantially stabilized anionic P‐nucleophiles to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism, which involves both concerted and stepwise SNAr reaction pathways.
https://ift.tt/2JuUiXJ
Both electron‐neutral and electron‐rich non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr) reaction. Even substantially stabilized anionic P nucleophiles reacted to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism involving both concerted and stepwise SNAr reaction pathways (see scheme).
Abstract
Non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr) reaction. Remarkably, both electron‐neutral and electron‐rich aryl fluorides participated in the reaction with substantially stabilized anionic P nucleophiles to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism that involves both concerted and stepwise SNAr reaction pathways.
https://ift.tt/3lpVSHm
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c09296
https://ift.tt/3jbQqax
Non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr). Remarkably, both electron‐neutral and electron‐rich aryl fluorides participated in the reaction with substantially stabilized anionic P‐nucleophiles to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism, which involves both concerted and stepwise SNAr reaction pathways.
https://ift.tt/3qnMVSI
Non‐activated aryl fluorides reacted with potassium diorganophosphinites through a nucleophilic aromatic substitution (SNAr). Remarkably, both electron‐neutral and electron‐rich aryl fluorides participated in the reaction with substantially stabilized anionic P‐nucleophiles to form the corresponding tertiary phosphine oxides. Quantum chemical calculations suggested a nucleophile‐dependent mechanism, which involves both concerted and stepwise SNAr reaction pathways.
https://ift.tt/3lpVSHm
https://preview.redd.it/zm83wycfsyw61.png?width=682&format=png&auto=webp&s=d98a2f11195184d499a066012bab29d908d67330
