Robby Vroemans

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10 Feb 16:40

[ASAP] Using Chlorotrifluoroethane for Trifluoroethylation of (Hetero)aryl Bromides and Chlorides via Nickel Catalysis

by Xuefei Li, Xing Gao, Chun-Yang He, and Xingang Zhang

TOC Graphic

Organic Letters
DOI: 10.1021/acs.orglett.1c00058
10 Feb 16:32

[ASAP] How Solvents Control the Chemoselectivity in Rh-Catalyzed Defluorinated [4 + 1] Annulation

by Shihan Liu, Lei Zhu, Tao Zhang, Kangbao Zhong, Shi-Jun Li, Ruopeng Bai, and Yu Lan

TOC Graphic

Organic Letters
DOI: 10.1021/acs.orglett.1c00223
10 Feb 16:31

Hydrogen‐Borrowing Alkylation of 1,2‐Amino Alcohols in the Synthesis of Enantioenriched γ‐Aminobutyric Acids

by Christopher J. J. Hall, William R. F. Goundry, Timothy James Donohoe
Hydrogen‐Borrowing Alkylation of 1,2‐Amino Alcohols in the Synthesis of Enantioenriched γ‐Aminobutyric Acids

The scope of carbon–carbon bond‐forming hydrogen‐borrowing reactions has been expanded to include 1,2‐amino alcohols derived from both natural and unnatural amino acids. The vulnerable amine stereocentre is preserved in the reaction by the use of a bulky nitrogen protecting group (trityl or benzyl), with the products being readily cleaved under acidic conditions to the corresponding γ‐aminobutyric acids without further purification.


Abstract

For the first time we have been able to employ enantiopure 1,2‐amino alcohols derived from abundant amino acids in C−C bond‐forming hydrogen‐borrowing alkylation reactions. These reactions are facilitated by the use of the aryl ketone Ph*COMe. Racemisation of the amine stereocentre during alkylation can be prevented by the use of sub‐stoichiometric base and protection of the nitrogen with a sterically hindered triphenylmethane (trityl) or benzyl group. The Ph* and trityl groups are readily cleaved in one pot to give γ‐aminobutyric acid (GABA) products as their HCl salts without further purification. Both steps may be performed in sequence without isolation of the hydrogen‐borrowing intermediate, removing the need for column chromatography.

10 Feb 16:27

Synthesis of Fluoro‐, Monofluoromethyl‐, Difluoromethyl‐, and Trifluoromethyl‐Substituted Three‐Membered Rings

by Jonathan Decaens, Samuel Couve‐Bonnaire, André B. Charette, Thomas Poisson, Philippe Jubault
Synthesis of Fluoro‐, Monofluoromethyl‐, Difluoromethyl‐, and Trifluoromethyl‐Substituted Three‐Membered Rings

Better with three: Fluorinated three‐membered rings are valuable compounds with many applications. In this Minireview, the synthesis of fluoro‐, monofluoromethyl‐, difluoromethyl‐, and trifluoromethyl‐substituted cyclopropanes, cyclopropenes, aziridines, azirines, epoxides, and thiiranes over the past decade are described.


Abstract

This Minireview describes recent advances toward the synthesis of fluoro‐, monofluoromethyl‐, difluoromethyl‐, and trifluoromethyl‐substituted three‐membered rings such as cyclopropanes, aziridines, epoxides, episulfides, cyclopropenes, and 2 H‐azirines. The main synthetic methodologies since 2016 for cyclopropanes and since 2010 for the other three‐membered rings are reported.

10 Feb 16:27

In Vitro and In Vivo Sequestration of Phencyclidine by Me4Cucurbit[8]uril**

by Steven Murkli, Jared Klemm, Adam T. Brockett, Michael Shuster, Volker Briken, Matthew R. Roesch, Lyle Isaacs
In Vitro and In Vivo Sequestration of Phencyclidine by Me4Cucurbit[8]uril**

Be my guest: We report the binding affinity of CB[8] and its water soluble analogue Me4CB[8] toward a panel of 10 drugs of abuse by isothermal titration calorimetry. The Me4CB[8]⋅PCP complex is particularly tight with K d=2 nm in 20 mm NaH2PO4 buffered H2O at pH 7.4. Me4CB[8] is well tolerated according to the results of in vitro cytotoxicity assays and in vivo (mice) maximum tolerated dose studies. The hyperlocomotion of swiss webster mice dosed with PCP can be controlled by the (pre)treatment with Me4CB[8].


Abstract

We report investigations of the use of cucurbit[8]uril (CB[8]) macrocycles as an antidote to counteract the in vivo biological effects of phencyclidine. We investigate the binding of CB[8] and its derivative Me4CB[8] toward ten drugs of abuse (3–9, 12–14) by a combination of 1H NMR spectroscopy and isothermal titration calorimetry in phosphate buffered water. We find that the cavity of CB[8] and Me4CB[8] are able to encapsulate the 1‐amino‐1‐aryl‐cyclohexane ring system of phencyclidine (PCP) and ketamine as well as the morphinan skeleton of morphine and hydromorphone with K d values ≤50 nm. In vitro cytotoxicity (MTS metabolic and adenylate kinase cell death assays in HEK293 and HEPG2 cells) and in vivo maximum tolerated dose studies (Swiss Webster mice) which were performed for Me4CB[8] indicated good tolerability. The tightest host⋅guest pair (Me4CB[8]⋅PCP; K d=2 nm) was advanced to in vivo efficacy studies. The results of open field tests demonstrate that pretreatment of mice with Me4CB[8] prevents subsequent hyperlocomotion induction by PCP and also that treatment of animals previously dosed with PCP with Me4CB[8] significantly reduces the locomotion levels.

10 Feb 16:25

A Synthetic Strategy for Cofacial Porphyrin‐Based Homo‐ and Heterobimetallic Complexes

by Christoph Schissler, Erik K. Schneider, Benjamin Felker, Patrick Weis, Martin Nieger, Manfred M. Kappes, Stefan Bräse
A Synthetic Strategy for Cofacial Porphyrin‐Based Homo‐ and Heterobimetallic Complexes

Simple route to dimeric complexes: Three different types of covalently linked metalloporphyrin dimers were synthesized. The monomers were synthesized sequentially and can be filled with metals before linking. As a result, different heterobimetallic systems can be made. Depending on the metals M1 and M2 used (M=Mn, Fe, Ni, Cu, Zn, Pd), a wide range of potentially catalytically active species can be prepared, such as analogues of carbon monoxide dehydrogenase.


Abstract

We present a straightforward and generally applicable synthesis route for cofacially linked homo‐ and heterobimetallic porphyrin complexes. The protocol allows the synthesis of unsymmetrical aryl‐based meso‐meso as well as β‐meso‐linked porphyrins. Our method significantly increases the overall yield for the published compound known as o‐phenylene‐bisporphyrin (OBBP) by a factor of 6.8. Besides the synthesis of 16 novel homobimetallic complexes containing MnIII, FeIII, NiII, CuII, ZnII, and PdII, we achieved the first single‐crystal X‐ray structure of an unsymmetrical cofacial benzene‐linked porphyrin dimer containing both planar‐chiral enantiomers of a NiII 2 complex. Additionally, this new methodology allows access to heterobimetallic complexes such as the FeIII‐NiII containing carbon monoxide dehydrogenase active site analogue. The isolated species were investigated by various techniques, including ion mobility spectrometry, DFT calculations, and UV/Vis spectroscopy. This allowed us to probe the influence of interplane distance on Soret band splitting.

09 Feb 10:43

Manganese catalyzed C-alkylation of methyl N-heteroarenes with primary alcohols

Chem. Commun., 2021, 57,3026-3029
DOI: 10.1039/D1CC00181G, Communication
Akash Jana, Amol Kumar, Biplab Maji
C-Alkylations of nine different classes of methyl-substituted N-heteroarenes are disclosed using a bench stable Mn(I)-catalyst under borrowing hydrogen conditions.
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09 Feb 08:06

Cross-coupling reactions with esters, aldehydes, and alcohols

Chem. Commun., 2021, 57,2591-2604
DOI: 10.1039/D0CC08389E, Feature Article
Yan-Long Zheng, Stephen G. Newman
This feature article describes how diverse oxygen-containing functional groups such as esters, aldehydes, and alcohols can participate in cross-coupling reactions to prepare amides, ketones, alcohols, and beyond.
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09 Feb 08:03

C−N Axial Chiral Hypervalent Iodine Reagents: Catalytic Stereoselective α‐Oxytosylation of Ketones

by Haifa Alharbi, Mohamed Elsherbini, Jihan Qurban, Thomas Wirth
C−N Axial Chiral Hypervalent Iodine Reagents: Catalytic Stereoselective α‐Oxytosylation of Ketones

Novel C‐N axial chiral iodoarenes enable catalytic stereoselective α‐oxytosylations of ketones with high yields and improved enantioselectivities.


Abstract

A simple synthesis of a library of novel C−N axially chiral iodoarenes is achieved in a three‐step synthesis from commercially available aniline derivatives. C−N axial chiral iodine reagents are rarely investigated in the hypervalent iodine arena. The potential of the novel chiral iodoarenes as organocatalysts for stereoselective oxidative transformations is assessed using the well explored, but challenging stereoselective α‐oxytosylation of ketones. All investigated reagents catalyse the stereoselective oxidation of propiophenone to the corresponding chiral α‐oxytosylated products with good stereochemical control. Using the optimised reaction conditions a wide range of products was obtained in generally good to excellent yields and with good enantioselectivities.

03 Feb 15:47

Photocatalyzed Transition‐Metal‐Free Oxidative Cross‐Coupling Reactions of Tetraorganoborates**

by Arif Music, Andreas N. Baumann, Florian Boser, Nicolas Müller, Florian Matz, Thomas C. Jagau, Dorian Didier
Photocatalyzed Transition‐Metal‐Free Oxidative Cross‐Coupling Reactions of Tetraorganoborates**

Shining light on organoborates: A photocatalyzed oxidative cross‐coupling reaction of functionalized organoborates is described, providing a diverse range of biaryl and olefin products. The mechanism of this C−C bond formation was investigated through quantum chemical calculations, revealing an unusual boracyclic intermediate.


Abstract

Readily accessible tetraorganoborate salts undergo selective coupling reactions under blue light irradiation in the presence of catalytic amounts of transition‐metal‐free acridinium photocatalysts to furnish unsymmetrical biaryls, heterobiaryls and arylated olefins. This represents an interesting conceptual approach to forge C−C bonds between aryl, heteroaryl and alkenyl groups under smooth photochemical conditions. Computational studies were conducted to investigate the mechanism of the transformation.