Volume 8 Issue 3, March 2016

Volume 8 Issue 3

The Bergman cyclization is an eponymous chemical reaction in which an enediyne is converted into a benzene derivative via a diradical intermediate. Now, Leo Gross and co-workers have shown that it is possible to use an atomic force microscope (AFM) to induce a reversible Bergman cyclization in an anthracene diradical sitting on an ultrathin NaCl film. The tricyclic anthracene framework can be converted into a bicyclic system that has a 6- and a 10-membered ring. This molecule contains an enediyne moiety that can then be cyclized to reform the original anthracene framework. The cover shows an AFM image of one of the 10-6 bicyclic molecules anchored to a NaCl step edge.Article p220IMAGE: BRUNO SCHULER, IBM RESEARCH – ZURICHCOVER DESIGN: KAREN MOORE

Commentary

  • Commentary |

    Publishing the wrong interpretation of experimental data can result in an immediate horde of chemists feeding on the error like vultures. On rare occasions, this phenomenon can open up an entire new field of science — and the structure of ferrocene is a case in point.

    • Jeffrey I. Seeman
    •  & Stuart Cantrill

News and Views

  • News & Views |

    Vaccination with a synthetic glycoconjugate, in combination with the administration of an inhibitor that blocks capsular polysaccharide synthesis in bacteria, could offer an alternative route to combat bacterial infections.

    • David Bundle
  • News & Views |

    Emulating the efficiency with which enzymes catalyse reactions has often been used as inspiration to develop self-assembled cages. Now two studies present approaches to achieving catalyst turnover — one of the biggest challenges in achieving truly biomimetic catalysis.

    • Richard J. Hooley
  • News & Views |

    The use of renewable resources as providers to the electrical grid is hampered by the intermittent and irregular nature in which they generate energy. Electrical energy storage technology could provide a solution and now, by using an iterative design process, a promising anolyte for use in redox flow batteries has been developed.

    • Wei Wang
    •  & Vince Sprenkle
  • News & Views |

    While there is some qualitative understanding of how excess protons behave in acidic aqueous solutions, there is still much to learn about the structures they form with water molecules. Now, 2D infrared spectroscopy has enabled the definite identification of the 'Zundel cation' in protonated liquid water and an approximate determination of its lifetime.

    • Noam Agmon

Review

  • Review Article |

    In a remote functionalization, reaction occurs at a site distant from the site of initial activation. This Review discusses attempts to achieve this challenging goal with a particular focus on reactions that exploit alkene isomerizations to effect transit of the catalyst from a reactive alkene to a distant sp3 centre.

    • Alexandre Vasseur
    • , Jeffrey Bruffaerts
    •  & Ilan Marek

Articles

  • Article |

    The Bergman cyclization is a fascinating rearrangement reaction with implications beyond organic chemistry. It has now been shown that a reversible Bergman cyclization reaction in a single molecule sitting on an ultrathin NaCl film can be triggered and directly imaged using atomic force microscopy. The interconverted diradical and diyne products are shown to have distinct chemical and physical properties.

    • Bruno Schuler
    • , Shadi Fatayer
    • , Fabian Mohn
    • , Nikolaj Moll
    • , Niko Pavliček
    • , Gerhard Meyer
    • , Diego Peña
    •  & Leo Gross
  • Article |

    Preorganization of catalysts and substrates can lead to significant rate enhancement—an effect often observed in enzyme catalysis. Now, a self-assembled nanosphere equipped with 24 guanidinium binding sites is demonstrated to strongly bind sulfonate-containing gold catalysts. Base-triggered co-encapsulation of carboxylate containing substrates leads to pronounced gating effects and dramatically enhanced reaction rates.

    • Qi-Qiang Wang
    • , Sergio Gonell
    • , Stefan H. A. M. Leenders
    • , Maximilian Dürr
    • , Ivana Ivanović-Burmazović
    •  & Joost N. H. Reek
  • Article |

    The Kemp elimination has been catalysed in the cavity of a coordination cage with a rate enhancement (kcat/kuncat) of 200,000 at pD 8.5. The catalysis requires two orthogonal interactions to bring together the components: hydrophobic binding of benzisoxazole, and accumulation of hydroxide ions at the cationic cage surface by ion-pairing.

    • William Cullen
    • , M. Cristina Misuraca
    • , Christopher A. Hunter
    • , Nicholas H. Williams
    •  & Michael D. Ward
  • Article |

    Metal centres play an important role in the damage to biomolecules caused by radiation, but the respective microscopic mechanisms are unknown. Now it is shown that the absorption of X-rays by a metal ion leads to an intricate chain of ultrafast relaxation steps that results in the complete degradation of the metal's local environment.

    • V. Stumpf
    • , K. Gokhberg
    •  & L. S. Cederbaum
  • Article |

    The presence and linkage of unusual higher sugars in the ‘inner core’ of Gram-negative bacteria makes the core lipopolysacchride tetrasaccharide Hep2Kdo2 a tough target. Now, a 2+2 glycosylation strategy has facilitated the synthesis of this glycoconjugate. Synthesis of Hep2Kdo2 enabled an antibacterial vaccination strategy based on immunization with the glycoconjugate and the subsequent administration of an inhibitor that uncovers the corresponding epitope in pathogenic bacteria.

    • Lingbing Kong
    • , Balakumar Vijayakrishnan
    • , Michael Kowarik
    • , Jin Park
    • , Alexandra N. Zakharova
    • , Larissa Neiwert
    • , Amirreza Faridmoayer
    •  & Benjamin G. Davis
  • Article |

    Interpenetration of metal–organic frameworks (MOFs) is a common phenomenon, in which a structure consists of two or more identical, entangled sub-lattices. Now, MOFs with variable, fractional degrees of occupancy of one of two sub-lattices have been prepared. The extent of interpenetration can be controlled either during synthesis or by autocatenation, a framework rearrangement process.

    • Alan Ferguson
    • , Lujia Liu
    • , Stefanus J. Tapperwijn
    • , David Perl
    • , François-Xavier Coudert
    • , Stijn Van Cleuvenbergen
    • , Thierry Verbiest
    • , Monique A. van der Veen
    •  & Shane G. Telfer
  • Article |

    Until recently, the three-body recombination reaction was widely regarded as the only reaction pathway to the production of molecular oxygen in Earth's prebiotic primitive atmosphere. Observation of a CO2 photodissociation pathway altered this view, but now, using anion velocity imaging, a further source of molecular oxygen is revealed, formed via the dissociative electron attachment to CO2.

    • Xu-Dong Wang
    • , Xiao-Fei Gao
    • , Chuan-Jin Xuan
    •  & Shan Xi Tian
  • Article |

    Self-replicating molecules provide a simple molecular level system to study the processes occurring in speciation. Now it is shown that in a pool of interconverting macrocycles, constructed from two building blocks, two distinct sets of self-replicating molecules emerge, and that one is a descendant of the other.

    • Jan W. Sadownik
    • , Elio Mattia
    • , Piotr Nowak
    •  & Sijbren Otto
  • Article |

    Highly compressible crystalline materials typically rely on the high compressibility of their chemical bonds. Now, a family of LnFe(CN)6 frameworks (Ln = Ho, Lu or Y) has been shown to exhibit pronounced volumetric and linear compressibilities through a spring-and-gear mechanism instead, in which a torsionally flexible LnN6 unit twists reversibly under pressure.

    • Samuel G. Duyker
    • , Vanessa K. Peterson
    • , Gordon J. Kearley
    • , Andrew J. Studer
    •  & Cameron J. Kepert
  • Article |

    Enantioselective aldol reactions with fluoroacetate would enable access to numerous fluorinated analogues of therapeutically important compounds but have been a long-standing unsolved challenge. Now, bioinspired fluoromalonic acid half thioesters (F-MAHTs) have been devised and allow for highly stereoselective reactions with aldehydes under mild organocatalytic conditions.

    • Jakub Saadi
    •  & Helma Wennemers

In Your Element

  • In Your Element |

    Yuichiro Nagame ponders on the steps it took to make lawrencium, and its location in the periodic table.

    • Yuichiro Nagame

Correction

Corrigenda