Herein we report an asymmetric two-component vinylogous Catellani reaction for the construction of C–N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process. Various partially aromatic iodinated 2-pyridones, quinolones, coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group, to afford a wide variety of polycyclic C–N atropisomers (39 examples, up to 97% ee ). The obtained C–N axial chirality is originated from the preformed transient C–C axial chirality with high fidelity. The synthetic utility of this chemistry is demonstrated by facile preparation of complex quinoline and pyridine based C–N atropisomers through a N -deprotection and aromatization sequence. In addition, a remote axial-to-central diastereoinduction process dictated by C–N axial chirality is observed with excellent diastereocontrol. This research opens a new avenue for asymmetric synthesis.

https://ift.tt/2SpJdva

A Rh‐catalyzed asymmetric synthesis of silicon‐stereogenic dihydrodibenzosilines featuring axially chiral 6‐member‐bridged biaryls is demonstrated. In the presence of Rh(I) catalyst with chiral diphosphine ligand, a wide range of dihydrodibenzosilines containing both silicon‐central and axial chiralities are conveniently constructed in excellent enantioselectivities via dehydrogenative Csp3−H silylation. Absolute configuration analysis by single crystal X‐ray structures revealed a novel silicon‐central to axial chirality relay phenomenon, which we believe will inspire further research in the field of asymmetric catalysis and chiroptical materials.

https://ift.tt/3d4TZz3

Chiral C−N axis is efficiently set up through an NHC organocatalytic atroposelective cycloaddition reaction, with axially chiral thiazine molecules obtained in excellent optical purities.

Abstract

A catalytic atroposelective cycloaddition reaction between thioureas and ynals is developed. This reaction features the first NHC‐catalyzed addition of thioureas to acetylenic acylazolium intermediates to eventually set up C−N axial chirality with excellent optical purities. The obtained axially chiral thiazine derivative products bear multiple functional groups and are feasible for further transformations.

https://ift.tt/3lulOU0

Single and double cyclophenylene‐ethynylenes (CPEs) with axial and helical chirality have been synthesized by the Sonogashira cross‐coupling of di‐ and tetra‐ethynyl biphenyls with a U‐shaped prearomatic diiodoparaphenylene followed by reductive aromatization. X‐ray crystallographic analyses and the DFT calculations revealed that these CPEs possess highly twisted bent structures. Bend angles on the edge of the paraphenylene units were close to the value of [5]cycloparaphenylene (CPP), the smallest CPP to date. Not only the double CPE but also the single CPE possessed stable chirality despite its flexible biphenyl structure due to the high strain in the diethynyl‐paraphenylene moiety. In both the single and double CPEs, orbital interactions along the biphenyl axis were observed by DFT calculations in LUMO and LUMO+2 of the single CPE and LUMO+1 of the double CPE, which were likely to cause the lowering of these orbital energies. Concerning chiroptical property, boosting of the g abs value was observed in the biphenyl‐based double CPE, as well as the binaphthyl‐based single CPE, compared to the biphenyl‐based single CPE.

https://ift.tt/2VIDdfU

Can someone explain me the difference between axial and chiral chirality ? thanks :)

A new class of axially chiral styrene-based thiourea-tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements and multiple activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo-, diastereo- and enantioselective (2+4) cyclization of 2-benzothiazolimines with homophthalic anhydrides in good yields (up to 96%) with excellent stereoselectivities (all >95:5 dr, up to 98% ee). More importantly, theoretical calculations elucidated the important role of axially chiral styrene moiety in controlling both the reactivity and the enantioselectivity. This work not only represents the first design of styrene-based chiral thiourea-tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2-benzothiazolimines, but also gives an in-depth understanding of axially chiral styrene-based organocatalysts.

https://ift.tt/3xH2jO8

Rhodium-catalyzed C−H activation of nitrones and coupling with different classes of sterically hindered alkynes afforded C−C or C−N atropochiral and C-centered point-chiral indenes in excellent enantio- and diastereoselectivity. The chiral center and axis are disposed in a distal fashion, and they are constructed via two uncorrelated stereo-determining steps.

Abstract

Reported herein is asymmetric [3+2] annulation of arylnitrones with different classes of alkynes catalyzed by chiral rhodium(III) complexes, with the nitrone acting as an electrophilic directing group. Three classes of chiral indenes/indenones have been effectively constructed, depending on the nature of the substrates. The coupling system features mild reaction conditions, excellent enantioselectivity, and high atom-economy. In particular, the coupling of N-benzylnitrones and different classes of sterically hindered alkynes afforded C−C or C−N atropochiral pentatomic biaryls with a C-centered point-chirality in excellent enantio- and diastereoselectivity (45 examples, average 95.6 % ee). These chiral center and axis are disposed in a distal fashion and they are constructed via two distinct migratory insertions that are stereo-determining and are under catalyst control.

https://ift.tt/3yM5xir

Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c04759

Meng-Meng Xu, Xin-Yu You, Yu-Zhen Zhang, Yang Lu, Kui Tan, Limin Yang, and Quan Cai

https://ift.tt/35jHg6V

The N‐heterocyclic carbene catalyzed enantioselective de novo synthesis of axially chiral benzothiophene/benzofuran‐fused biaryls from enals and 2‐benzylbenzothiophene/benzofuran‐3‐carbaldehydes has been developed. This cascade process comprises a [2+4] annulation, decarboxylation, and oxidative aromatization with central‐to‐axial chirality conversion, allowing rapid access to atropoisomeric tri‐ and tetra‐ortho‐substituted biaryls with high enantioselectivities.

Abstract

Axially chiral biaryl scaffolds are prevalent in natural products, chiral ligands, and organocatalysts. However, N‐heterocyclic carbene (NHC) catalyzed de novo construction of an aromatic ring with concomitant axial chirality induction for the synthesis of biaryl atropisomers is far less developed, and the efficient synthesis of axially chiral tetra‐ortho‐substituted biaryls remains an unsolved problem under NHC catalysis. Reported here is an NHC‐catalyzed de novo synthesis of axially chiral benzothiophene/benzofuran‐fused biaryls from enals and 2‐benzyl‐benzothiophene/benzofuran‐3‐carbaldehydes through a [2+4] annulation, decarboxylation, and oxidative aromatization cascade with central‐to‐axial chirality conversion. The developed method provides efficient and general access to novel axially chiral benzothiophene/benzofuran‐fused biaryls in high enantioselectivities and works well for the synthesis of tetra‐ortho‐substituted biaryls.

https://ift.tt/3mPezXo

Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c00640

Fan Teng, Ting Yu, Yan Peng, Weiming Hu, Huaanzi Hu, Yimiao He, Shuang Luo, and Qiang Zhu

https://ift.tt/3jDTwoT

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c08948

Sitthichok Kasemthaveechok, Laura Abella, Marion Jean, Marie Cordier, Thierry Roisnel, Nicolas Vanthuyne, Thierry Guizouarn, Olivier Cador, Jochen Autschbach, Jeanne Crassous, and Ludovic Favereau

https://ift.tt/3pCbAm3

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c00208

https://ift.tt/32TBG9F

The first example of tetracyanobuta‐1,3‐diene‐based derivatives, showing unprecedented configurational stability and a peculiar light‐triggered enantiomer conversion mechanism enabled by triple‐state photogeneration, is reported.

Abstract

In recent years, several tetracyanobuta‐1,3‐diene (TCBD) conjugates have been prepared by linking the tetracyano unit to various electroactive moieties. These push–pull conjugates, besides showing interesting physicochemical properties, are axially chiral, a feature arising from the restricted rotation around the central bond of the butadiene. Yet, only in a few cases, separation and isolation of the enantiomers have been successfully achieved, owing to the configurational lability of the corresponding enantiopure species. Herein, we report the first example of photo‐ and electroactive TCBD‐based derivatives showing unprecedented configurational stability and a peculiar light‐triggered enantiomer conversion mechanism enabled by triple‐state photogeneration. These systems represent a nice addition to the fast‐increasing arsenal of artificial, light‐controllable molecular switches.

https://ift.tt/3fu4tpv

Don't turn N‐C! Atropo‐enantioselective N−C coupling was achieved with excellent enantioselectivity at room temperature with a simple catalytic system. The key to solving this long‐standing challenge was the use of a chiral Cu catalyst in combination with hypervalent iodine reagents as coupling partners.

Abstract

N−C axially chiral compounds have emerged recently as appealing motifs for drug design. However, the enantioselective synthesis of such molecules is still poorly developed and surprisingly no metal‐catalyzed atroposelective N‐arylations have been described. Herein, we disclose an unprecedented Cu‐catalyzed atroposelective N−C coupling that proceeds at room temperature. Such mild reaction conditions, which are a crucial parameter for atropostability of the newly generated products, are operative thanks to the use of hypervalent iodine reagents as a highly reactive coupling partners. A large panel of the N−C axially chiral compounds was afforded with very high enantioselectivity (up to >99 % ee) and good yields (up to 76 %). Post‐modifications of thus accessed atropisomeric compounds allows further expansion of the diversity of these appealing compounds.

https://ift.tt/2xtpvUV

Let′s twist again: Axially chiral molecules with thermally activated delayed fluorescence and circularly polarized electroluminescence (CPEL) are presented. CP‐OLEDs based on these molecules display high efficiencies and blue CPEL with large gEL values.

Abstract

The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is proposed. A pair of chiral stable enantiomers, (−)‐(S)‐Cz‐Ax‐CN and (+)‐(R)‐Cz‐Ax‐CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π‐conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (ΔEST) of 0.029 eV and mirror‐image circularly polarized luminescence (CPL) activities with large glum values. Notably, CP‐OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with gEL values of −1.2×10−2 and +1.4×10−2, respectively. These are the first CP‐OLEDs based on TADF‐active enantiomers with efficient blue CPEL.

https://ift.tt/3988yNY

Enantioselective construction of axially chiral compounds by the electrophilic carbothiolation of alkynes is disclosed. This transformation is enabled by the use of a tosyl‐protected bifunctional sulfide catalyst and mesyl‐protected ortho‐alkynylaryl amines. The obtained products can easily be converted into biaryl amino sulfides, biaryl amino sulfoxides, biaryl amines, vinyl–aryl amines, and other valuable difunctionalized compounds.

Abstract

The enantioselective construction of axially chiral compounds by electrophilic carbothiolation of alkynes is disclosed for the first time. This enantioselective transformation is enabled by the use of a Ts‐protected bifunctional sulfide catalyst and Ms‐protected ortho‐alkynylaryl amines (Ts=tosyl; Ms=mesyl). Both electrophilic arylthiolating and electrophilic trifluoromethylthiolating reagents are suitable for this reaction. The obtained products of axially chiral vinyl–aryl amino sulfides can be easily converted into biaryl amino sulfides, biaryl amino sulfoxides, biaryl amines, vinyl–aryl amines, and other valuable difunctionalized compounds.

https://ift.tt/37mE8q7

A free amine group can be used as a directing group to synthesize axially chiral biaryl compounds by a PdII‐catalyzed atroposelective C−H olefination. Good yields and high enantioselectivities (up to 97 % ee) can be achieved by using chiral spiro phosphoric acid (SPA) as an efficient ligand. The amount of ligand can be reduced to 1 mol % without loss of enantiocontrol in a gram‐scale synthesis.

Abstract

A simple and ubiquitously present group, free amine, is used as a directing group to synthesize axially chiral biaryl compounds by PdII‐catalyzed atroposelective C−H olefination. A broad range of axially chiral biaryl‐2‐amines can be obtained in good yields with high enantioselectivities (up to 97 % ee). Chiral spiro phosphoric acid (SPA) proved to be an efficient ligand and the loading could be reduced to 1 mol % without erosion of enantiocontrol in gram‐scale synthesis. The resulting axially chiral biaryl‐2‐amines also provide a platform for the synthesis of a set of chiral ligands.

https://ift.tt/39NfMHE

Journal of the American Chemical SocietyDOI: 10.1021/jacs.9b12205

https://ift.tt/391bv2n

Journal of the American Chemical SocietyDOI: 10.1021/jacs.9b13019

https://ift.tt/36ZlwfK

Journal of the American Chemical SocietyDOI: 10.1021/jacs.9b13549

https://ift.tt/392afMb

Things that an Engineer or Science Officer on a star ship might say.

1. We’ve got a Warp Core breach
2. Get the ion matrix modulator back online
3. The gravimetric stabilizer is loose
4. A quantum matrix relay
5. Reroute power to the forward flux capacitor
6. Reverse polarity to theta radiation
7. Demodulate the deflector emitters
8. The Tridium particles are unstable
9. A Resonance Distortion in the Inductors
10. The Plasma Manifold can’t handle the flux
11. We must calculate the iridium three-factor conductors
12. Converge the radiation filters to infra-segmentation
13. Ion-pressure has reached critical matrix
14. Re-integrate the strontium-capacitor to redux-level
15. Restart the master chronium disruptor
16. Maximum astro turbilator integrated
17. Quantum-seed charged to energetic maximum
18. Thorium-flux source has been dispatched
19. Thermal integration detected
20. Astral velocity converted
21. Detonate the Illudium Q-35 explosive space modulator
22. Reverse the polarity of the neutron flow (Dr. Who)
23. There’s a malfunction in the retro-encabulator
24. Circadian extrapolation of the interpolation theorem
25. Spatial transposition phenomena
26. Inner realm qualia
27. Tripolar amalgamation theory
28. Single equation theory of the universal containment field
29. Modular neural interface component
30. Bio-cellular granularity
31. Holodistortion dome
32. Ecolyptic nervescaping processes
33. Micro-ontological effect syndrome
34. Brainlock ameliorator device
35. Mindquake predictor array
36. Achronic sterilization dilator
37. Noctilucent telescopy
38. Thanoscopic analyzer
39. Biotech construction units
40. Temporal augmentation
41. Subneural traweling graft
42. Bioware contamination particles
43. Nanogenetic augmentation cords
44. Helical supersemetric ray-bands
45. Monitored Cryonic Mini-Kelvin Rating
46. Quadra-Capacitor Circuitry
47. Virtual locutor telepresence
48. Genotypic avatar
49. Subspeciation matrix grid
50. Neuro-linked psi-bands
51. Dillinger-drive transfield component
52. Deploying frictionless vortals now, Sir
53. Enhance the divergence coefficient
54. We need to integrate the molecular cospology
55. Reconscede the Heisenberg drive
56. Activate the Omega 13 device
57. Reconfigure the nanowave frequency shift
58. You need to calibrate your ventral defragmenter
59. Reroute the secondary vacuum node
60. We’ve got a destabilized gluon pulse
61. Did you fractionalize the redundancy emitters?
62. I’m detecting a particle trace in the thr

I have been looking into k-uniform Euclidean tilings recently (https://en.wikipedia.org/wiki/List_of_k-uniform_tilings). As far as I know, their list is complete only to k=7.

I have made and implemented an algorithm (a variant of my previous tiling search approach) that can extend this list, and extend it significantly (I'm currently running it up to k=12, although this will take a few days to complete).

Here's the rub: I think that the algorithm is guaranteed to find every solution. (I haven't actually proven it, but the logic seems sound.) But the trouble is that the same solution can be (and usually is) found multiple times. Some solutions are actually found many times (particularly those that contain many similar vertex types such as the many, many solutions consisting of rows of squares and triangles alternating in some pattern).

I've been trying to go through the solutions by hand, but the potential for human error is too large. I managed to *almost* replicate the lists of 3-uniform and 4-uniform tilings from the Wikipedia, but I have always overlooked a few solutions (they were in the data set, I have just missed them).

I need help with devising some sort of pruning algorithm that could go over the result file and specifically point out unique solutions.

Some details: This is how a typical output looks:

Number of polygons: 10
(6,6,6)F, (3,3,6,6)F, (3,3,3,3,3,3)A2, (3,3,6,6)F, (3,3,3,3,6)F, (3,3,3,3,3,3)A2, (3,3,3,3,6)F, (3,3,3,3,6)F, (3,3,3,3,3,3)A2, (3,3,3,3,6)A
(6,6,6)F, (3,3,6,6)Fx2, (3,3,3,3,6)A, (3,3,3,3,6)Fx3, (3,3,3,3,3,3)A2x3
TES file: 10\10_36\3g 4e2 5a 5b3 6i3\eu raw 3g 4e2 5a 5b3 6i3 11.tes
(0 1')[1](2)(0' 2''')[2'](3' 2'')(0'' 2@4)(1'' 3''')(0''' 1@4)[1'''](0@4 1@6)[3@4](4@4 2@5)(0@5 4@7)(1@5 2@6)[0@6](3@6 3@7)(4@6 0@8)[0@7](1@7 0@9)(2@7 1@8)[2@8 2@9](3@9)
0: 0/1(6)-*1/*0(6)-*1'/*0'(6)-*2'''/*1'''(6)-1'''/2'''(6)-0'/1'(6)
1: 1/2(6)-2/0(6)-1'/2'(6)-*2'/*1'(6)-*0/*2(6)-*2/*1(6)
2: 2'/3'(3)-2''/*2''(3)-*3'/*2'(3)
3/4: 3'/0'(3)-2'''/3'''(3)-1''/2''(3)
*0'/*3'(3)-*2''/*1''(3)-*3'''/*2'''(3)
5/6: 0''/1''(3)-3'''/0'''(3)-1@4/2@4(3)
*1''/*0''(3)-*2@4/*1@4(3)-*0'''/*3'''(3)
7: *0''/0''(3)-2@4/3@4(3)-*3@4/*2@4(3)
8: 0'''/1'''(6)-*1'''/*0'''(6)-*1@4/*0@4(6)-*1@6/*0@6(6)-0@6/1@6(6)-0@4/1@4(6)
9: 3@4/4@4(3)-2@5/*2@5(3)-*4@4/*3@4(3)
10/11: 4@4/0@4(3)-1@6/2@6(3)-1@5/2@5(3)
*0@4/*4@4(3)-*2@5/*1@5(3)-*2@6/*1@6(3)
`12/1

>The number of achiral(axially-symmetric) necklaces with [;2n_1;] [;1;]s, [;2n_2;] [;2;]s, ..., [;2n_k;] [;k;]s is [;\binom{n_1 + n_2 + ... + n_k}{n_1 , n_2 , ... , n_k}=\frac{(n_1 +n_2 +...+n_k)!}{(n_1)!(n_2)!...(n_k)!};]

(Numbers 1 to n are instead of beads)

Necklace and bracelet: https://en.wikipedia.org/wiki/Necklace_(combinatorics)

This wikipedia page is mainly about making a necklace or bracelet with total of [;n;] beads with [;k;] types, but my topic is when the types and numbers of beads are given. This kind of problem has usually been solved by Burnside's lemma.

But I'm suggesting more basic methods, which uses the following equation:

[;{\rm(Number\;of\;bracelets)}=\frac{{\rm(Number\;of\;necklaces)+(Number\;of\;achiral\;necklaces)}}{2};]

This was complicating because we need to sort a lot of cases while counting the number of achiral necklaces, but my formula is about that and no complicating calculations are needed now on. Usually, we already calculate this value while counting the number of necklaces.

I think this method is better than using Burnside's lemma, because it doesn't demand to use brains. We do have to calculate some multinomial coefficient while counting the number of necklaces, but its calculation is way more easy than using Burnside's lemma, and it could be calculated mechanically. Once we get used to this formula, we even don't have to draw a circle!

Well back to the problem, example:

"What is the number of bracelets with 4 red and 4 blue beads?"

This kind of problem was very familiar to me, when I was a middle school student and studying Olympiad. The standard method I learned (before learning Burnside's lemma) to solve this is:

A. Count the number of necklaces

https://preview.redd.it/wv444xff1b381.png?width=2656&format=png&auto=webp&s=5ffdfa56036c23dc47417a2d46df87430adc7ba7

First, count the number of linear permutations about each period.

(divisor of 8)-period permutations: [;\binom{8}{4}=70;]

(divisor of 4)-period permutations: [;\binom{4}{2}=6;]

(divisor of 2)-period permutations: [;\binom{2}{1}=2;]

Then, properly subtract those values to get the number of exactly x-period permutations, divide it by period, and add them all.

8-period necklaces: [;\frac{70-6}{8}=8;]

4-period necklaces: [;\frac{6-2}{4}=1;]

2-period necklaces: [;\frac{2}{2}=1;]

The number of necklac

Just had my first exam and didn’t do the best, but I understand all the topics, just second guessed myself. All my initial answers were right, over thought in the last five minutes and changed half of my resonance, axial/equatorial, cis/trans answers. Does anyone have a turn around story for how they did in Orgo chem? Going from bad to good? I’m changing my study habits for the course and incorporating more practice problems and Khan Academy videos into it then before. Just looking for some motivation that could go along with a situation like mine, and study tips are much appreciated. Working on R and S stereochemistry, meso compounds, achiral/ chiral structures now.

[PART II] Morphinan History X - A Survey of Opioid Stereochemistry - Part II: Further Ring Fusions

REVIEW:

Part I of this monograph on opioid stereochemistry-ligand geometry established some foundational concepts such as stereospecific binding (SSB) [Goldstein, PNAS, 1971, v 68, p 1742], that is, the preferential affinity of one stereoisomer over another at bio receptors. Also explored were the steric effects of the most influential shared structural feature of the morphinan nucleus: cis-(1,3-diaxial) fusion of the imino-ethano system in the D-ring (Piperidine).

As a result of the nature of the constrained morphinan nucleus, this iminoethane bridge, anchored at C9 and C13, is forced to one side of the molecule. This provides steric hindrance which blocks access to the important C-ring of morphine derivs such as thebaine, forcing Diels-Alder cycloaddition to form the 6,14-endo adducts upon the reverse face of the C-ring.

Part I related how these steric limitations force dienophiles (during Diels-Alder rxn) to attack the diene system of thebaine from the least sterically hindered side of the morphinan nucleus (http://ineosopen.org/io2106r).

The electron-rich C-ring of thebaine allows for the ready cycloaddition of a diverse range of dienophiles leading to a range of Diels-Alder adducts [Tetrahedron, 1973, 29, 2387]. This includes unhindered dienophiles [KW Bentley, “The Alkaloids” (1971) v 13, p 75], substituted ethylenes [Tetrahedron, 1979, 30, 1201], nitroso carbonyls [JCS Perkin Trans I, 1981, p 3250] and nitroso arenes [JCS Perkin Trans I, 1979, p 3064].

The cycloaddition occurs under electronic control with C7-substitution occurring exclusively with very little, if any, isomeric C8-substituted product. Most of the adducts have 7-α stereochemistry. The notable exception to this being acrylonitrile dienophiles which favor 7-β formation [JACS, 1967, 89, 3267].

The most important takeaway from this molecular C-ring song-and-dance routine is the formation of the 6,14-endo***etheno bridge in a critical endo orientation on the reverse face of the morphinan nucleus, allowing for an important hydrogen bond interaction between the 19-O***H and 6-***O***CH3. While the 6-oxygen function is nonessential to high MOR affinity in the pentacyclic morphine series (cf. desomorphine has 10-fold morphine potency despite a complete lack of 6

Do your worst!

It really does, I swear!

For context I'm a Refuse Driver (Garbage man) & today I was on food waste. After I'd tipped I was checking the wagon for any defects when I spotted a lone pea balanced on the lifts.

I said "hey look, an escaPEA"

No one near me but it didn't half make me laugh for a good hour or so!

Edit: I can't believe how much this has blown up. Thank you everyone I've had a blast reading through the replies 😂

They’re on standbi

Buenosdillas

So, after my previous post about unusual hyperbolic tilings generated some interest, I tried to find a working hybrid tiling for one of the longer edges in my "edgecyclopedia" document. This time, it's edge 4.746040408980548, the edge of regular tiling {9,18}. It's the third longest edge with possible hybrid tilings I know (not counting the infinite families). Symbolically, it would be 2*arccosh(cos(pi/9)/sin(pi/18)).

Half of this edge, 2.3730202044902735, corresponds to a tiling involving two squares and 4 18-gons at a vertex.

So, I defined tiles for these three polygons (large enneagon and small square and 18-gon) and searched for tilings that combine these three together. And to be honest, that search is still ongoing, but it has produced its first batch of 12 solutions.

In all these solutions, the enneagons have axial symmetry, the squares have two diagonal axes of symmetry and the 18-gons are chiral, but have 9-fold rotational symmetry.

Here are the pictures of the first solution:

Enneagon-centered view

18-gon centered view

View centered on an 18-gon of the other chirality

Square-centered view

As you can see, it has two kinds of vertices. A square and 2 18-gons always form a straight angle, either against 9 enneagons or against an edge of a single enneagon. If I look at the results right, all 12 solutions are more or less the same, differing only in the details of how exactly are the enneagons connected.

A catalytic atroposelective cycloaddition reaction between thioureas and ynals is developed. Our reaction features the first NHC‐catalyzed addition of thioureas to acetylenic acylazolium intermediates to eventually set up C‐N axial chirality with excellent optical purities. The axially chiral thiazine derivative products from our reactions bear multiple functional groups and show promising synthetic applications and antimicrobial activities against Xanthomonas oryzae pv . oryzae that causes rice bacterial blight.

https://ift.tt/39FLtoo

Reported herein is asymmetric [3+2] annulation of arylnitrones with different classes of alkynes catalyzed by chiral rhodium(III) complexes, with the nitrone acting as an electrophilic directing group. Three classes of chiral indenes/indenones have been effectively constructed, depending on the nature of the substrates. The coupling system features mild reaction conditions, excellent enantioselectivity, and high atom-economy. In particular, the coupling of N -benzylnitrones and different classes of sterically hindered alkynes afforded C-C or C-N atropochiral pentatomic biaryls with a C-centered point-chirality in excellent enantio- and diastereoselectivity (45 examples, average 95.6% ee). These chiral center and axis are disposed in a distal fashion and they are constructed via two distinct migratory insertions that are stereo-determining.

https://ift.tt/3uZEaQE

Axially chiral biaryl scaffolds are prevalent in natural products, chiral ligands, and organocatalysts. However, NHC‐catalyzed de novo construction of aromatic ring with concomitant axially chiral induction for the synthesis of biaryl atropisomers is far less developed, and the efficient synthesis of axially chiral tetra‐ ortho ‐substituted biaryls remains an unsolved problem under NHC catalysis. Herein, we report an NHC‐catalyzed de novo synthesis of axially chiral benzothiophene/benzofuran‐fused biaryls from enals and 2‐benzyl‐benzothiophene/benzofuran‐3‐carbaldehydes through a cascade strategy of [2+4] annulation, decarboxylation, and oxidative aromatization with central‐to‐axial chirality conversion. The developed method provides an efficient and general access to novel axially chiral benzothiophene/benzofuran‐fused biaryls in high enantioselectivities and works well for the synthesis of tetra‐ ortho ‐substituted biaryls.

https://ift.tt/3mPezXo

In recent years, several tetracyanobuta‐1,3‐diene (TCBD) conjugates have been prepared by linking the tetracyano unit to various electroactive moieties. These push‐pull conjugates, besides showing interesting physicochemical properties, are axially chiral, a feature arising from the restricted rotation around the butadiene’s central bond. Yet, only in a few cases, enantiomers’ separation and isolation have been successfully achieved, owing to the configurational lability of the corresponding enantiopure species. Herein, we report on the first example of photo‐ and electroactive TCBD‐based derivatives showing unprecedented configurational stability and a peculiar light‐triggered enantiomer conversion mechanism enabled by triple‐state photogeneration. These systems represent a nice addition to the fast‐increasing arsenal of artificial, light‐controllable molecular switches.

https://ift.tt/3fu4tpv

N‐C axially chiral compounds have emerged recently as appealing motifs for drug design. However, enantioselective synthesis of such molecules is still poorly developed and surprisingly no metal‐catalyzed atroposelective N‐arylation have been described. Herein we disclose an unprecedented Cu‐catalyzed atroposelective N‐C coupling, occurring at room temperature. Such mild reaction conditions, crucial parameter to warrant atropostability of the newly generated products may be reached thank to the use of hypervalent iodines as highly reactive coupling partner. A large panel of the N‐C axially chiral compounds is hence afforded in very high enantioselectivities (up to > 99% ee) and good yields (up to 76%). Post‐modifications of thus accessed atropisomeric compounds allows further expanding the diversity of these appealing compounds.

https://ift.tt/2xtpvUV

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c01963

https://ift.tt/3emsWhg

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c05283

https://ift.tt/3ekznQR

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c02686

https://ift.tt/2ygRUOa