Florian Fischer

Caught in the net: The standard roles that the actors (nucleophile, electrophile, and catalyst) perform during the catalytic act in the arena of bifunctional catalysis were switched in the search for bioinspired organocatalysts. It was thus found that the network of hydrogen bonds provided by salan derivatives catalyzed the Mannich reaction of arylideneureas with acetoacetates in an enantioselective, biomimetic manner (see scheme).

[Communication]
Victor J. Lillo, Javier Mansilla, José M. Saá
Angew. Chem. Int. Ed., February 25, 2016, DOI: 10.1002/anie.201511555. Read article

Asymmetric reductive coupling of a ketone and amine is a straightforward and atom-economic approach for preparing optically enriched amines. The highly efficient and direct asymmetric reductive amination of arylacetones, catalyzed by an iridium complex, supplies enantiomerically pure β-arylamines. The new phosphoramidite ligands reported show superb reactivity and enantioselectivity in this reductive coupling. M.S.=molecular sieves, TFA=trifluoroacetic acid.

[Communication]
Haizhou Huang, Xiaoyan Liu, Le Zhou, Mingxin Chang, Xumu Zhang
Angew. Chem. Int. Ed., March 16, 2016, DOI: 10.1002/anie.201601025. Read article

Chlorination of arenes with chloride anions: The photochemical analogue of the enzymatic chlorination of Flavin-adenine dinucleotide (FAD)-dependent halogenases is possible in the presence of riboflavin, air, acetic acid, and blue light (see scheme: RFT=riboflavin tetraacetate).

[Communication]
Thea Hering, Bernd Mühldorf, Robert Wolf, Burkhard König
Angew. Chem. Int. Ed., March 17, 2016, DOI: 10.1002/anie.201600783. Read article

Dr. Dae-Hwan Park, M. Sc. Jaeyong Cho, Dr. Oh-Joon Kwon, Prof. Dr. Chae-Ok Yun and Prof. Dr. Jin-Ho Choy

Cancer therapy: An inorganic layered double hydroxide (LDH) nanovector with a folic acid (FA) conjugated surface showed siRNA-based cancer therapeutic efficacy in vivo through receptor-mediated active targeting (see picture). A 1.2-fold higher accumulation of the drug was achieved in tumor tissue, resulting in 3.0-fold higher suppression of tumor volume.

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Publication date: 9 March 2016
Source:Tetrahedron Letters, Volume 57, Issue 10
Author(s): Javad Safaei-Ghomi, Safura Zahedi
An efficient, one-pot, three-component protocol for the synthesis of a small library of chiral isoxazolidines and spiroisoxazolidines with high diastereoselectivity, from the reaction of N-arylhydroxylamines, arylaldehydes, isatins, and α,β-unsaturated aldehydes is described. l-Proline functionalized Fe3O4 nanoparticles as a magnetic organocatalyst gave isoxazolidine products in high yields as single isomers with an endo-configuration. Notable features of this methodology were: short reaction time, good to excellent yields, and use of an easily recovered heterogeneous catalyst that could be reused many times without significant loss of its catalytic activity.

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Publication date: 9 March 2016
Source:Tetrahedron Letters, Volume 57, Issue 10
Author(s): Anil Kumar Mutyala, Jong S. Park
Unsymmetrical trisulfonated zinc phthalocyanine with single carboxylic acid (trisulfo-Pc-COOH) was newly prepared via the hydrolysis of cyanotrisulfo-Pc which was obtained from the palladium catalyzed cyanation of iodotrisulfo-Pc. The product exhibited good water solubility along with excellent absorption and emission characteristics in an aqueous condition, proving its feasibility for use in bio-imaging applications.

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Publication date: 9 March 2016
Source:Tetrahedron Letters, Volume 57, Issue 10
Author(s): Yu Chen, Bo Chen, Daijun Luo, Yiyu Cai, Yaning Wei, Yifeng Han
A novel and simple depropargylation-triggered spontaneous cyclization reaction based fluorescent turn-on chemodosimeter for the detection of Pd²⁺ has been reasonably designed and developed. Based on the specific reactivity of palladium ion-promoted hydrolysis reaction, the probe exhibited a high selectivity and sensitivity for Pd²⁺ with a low detection limit (53nM, 5.7μg/L) under physiological conditions in neutral PBS (only containing 1% organic cosolvent) without any additional reagents.

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Simon M. Nicolle, Dr. William Lewis, Prof. Dr. Christopher J. Hayes and Prof. Dr. Christopher J. Moody

The metal-catalyzed reaction of diazocarbonyl compounds with β-aminoketone derivatives leads to highly substituted pyrrolidines with excellent diastereoselectivity under mild reaction conditions. The reaction starts as a metallocarbene N−H insertion but is diverted by an intermolecular aldol reaction.

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Escape artist extraordinaire: How shape-persistent is “shape-persistent”? Novel phenylene–ethynylene–butadiynylene rotaxanes synthesized by a covalent-template approach were found to undergo unthreading of the wheel from the axis (see picture). The detailed unthreading mechanism was investigated theoretically by state-of-the-art DFT-based molecular mechanics and a string method for the simulation of rare events.

[Communication]
Christopher Schweez, Philip Shushkov, Stefan Grimme, Sigurd Höger
Angew. Chem. Int. Ed., February 02, 2016, DOI: 10.1002/anie.201509702. Read article

Shine a little light: The first two-photon fluorescent formaldehyde probe, Na-FA, was engineered by condensation of a hydrazine moiety with FA. This unique strategy grants the probe highly favorable properties: a very large turn-on signal, a low detection limit, and a very fast onset, which collectively enable tracking of endogenous FA in living tissues for the first time.

[Communication]
Yonghe Tang, Xiuqi Kong, An Xu, Baoli Dong, Weiying Lin
Angew. Chem. Int. Ed., February 04, 2016, DOI: 10.1002/anie.201510373. Read article

Publication date: 17 February 2016
Source:Tetrahedron Letters, Volume 57, Issue 7
Author(s): Guang-Shou Feng, Yue Ji, Hui-Fang Liu, Lei Shi, Yong-Gui Zhou
An unusual solvent DMF-promoted dehydrogenation of 1-substituted 1,2,3,4-tetrahydroisoquinolines to synthesize cyclic imines is described. This environmentally friendly reaction features no requirement of any metal catalysts, oxidants, or hydrogen acceptors. A wide range of structurally varied 3,4-dihydroisoquinolines can be obtained with good yields and excellent chemoselectivities.

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Publication date: 24 February 2016
Source:Tetrahedron Letters, Volume 57, Issue 8
Author(s): Ying-Xue Yuan, Liang Wang, Yi-Fei Han, Fen-Fang Li, Hong-Bo Wang
A novel azo-thiourea based anion receptor can be synthesized by coupling a bis-azoaniline motif with butyl isothiocyanate with 45% yield under mild conditions. It was found that azo-thiourea was an excellent receptor to recognize various di-carboxylate anions. It can serve as a colorimetric sensor for azelate ion and led to a significant change in the absorption spectrum. Furthermore, a reversible trans–cis isomerization of azo-thiourea induced by visible lights was confirmed by ¹H NMR spectroscopy.

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