Molecular Ansa-Basket: Synthesis of Inherently Chiral All-Carbon [12](1,6)Pyrenophane

The synthesis of inherently chiral all-carbon C2-symmetric [12]­(1,6)­pyrenophane 1 is reported. The cyclophane 1 was obtained via a ring-closing alkyne metathesis reaction using Mortreux’s catalyst molybdenum hexacarbonyl and 2-fluorophenol as a phenol additive. The M and P enantiomers of the all-carbon pyrenophane 1 were demonstrated to be very stable in their enantiopure form even upon prolonged heating at 200 °C. [12]­(1,6)­Pyrenophane-6-yne 1 was fully characterized by high-resolution mass spectrometry, nuclear magnetic resonance, UV–vis, and measured and calculated electronic circular dichroism spectroscopy

Aqueous Assembly of Zwitterionic Daisy Chains

The synthesis and characterization of zwitterionic molecular [c2]‐ and [a2]‐daisy chains are described, relying on recognition of a positively charged cyclophane and a negatively charged oligo(phenylene‐ethynylene) (OPE) rod in aqueous medium. For this purpose, syntheses of an acetylene‐functionalized macrocyclic receptor and a water‐soluble OPE‐rod as the guest component are presented, from which a heteroditopic daisy chain monomer was prepared. This monomer aggregated strongly in water/methanol 4:1 and formed molecular daisy chains, which were isolated as interlocked species from a stoppering reaction at 1 mm concentration. The cyclic dimer [c2] was the main product with an isolated yield of 30 % and consisted of a mixture of diastereomers, as evidenced by 1H NMR spectroscopy

Mechanical Stabilization of Helical Chirality in a Macrocyclic Oligothiophene

We introduce a design principle to stabilize helically chiral structures from an achiral tetrasubstituted [2.2]paracyclophane by integrating it into a macrocycle. The [2.2]paracyclophane introduces a three-dimensional perturbation into a nearly planar macrocyclic oligothiophene. The resulting helical structure is stabilized by two bulky substituents installed on the [2.2]paracyclophane unit. The increased enantiomerization barrier enabled the separation of both enantiomers. The synthesis of the target helical macrocycle 1 involves a sequence of halogenation and cross-coupling steps and a high-dilution strategy to close the macrocycle. Substituents tuning the energy of the enantiomerization process can be introduced in the last steps of the synthesis. The chiral target compound 1 was fully characterized by NMR spectroscopy and mass spectrometry. The absolute configurations of the isolated enantiomers were assigned by comparing the data of circular dichroism spectroscopy with TD-DFT calculations. The enantiomerization dynamics was studied by dynamic HPLC and variable-temperature 2D exchange spectroscopy and supported by quantum-chemical calculations

Synthesis of trinorbornane

Herein we report the synthesis and characterisation of the until recently unreported chiral C-11 skeleton of tetracyclo[5.2.2.01,6.04,9]undecane ("trinorbornane'') which could be obtained in 7% overall yield in 9 steps. This new rigid structural type was found to be present in the computer generated Chemical Universe Data-base (GDB) and has until now no real-world counterpart

Huddle Up: Using Mediation to Help Settle the National Football League Labor Dispute

In a patient transferred from Togo to Cologne, Germany, Lassa fever was diagnosed 12 days post mortem. Sixty-two contacts in Cologne were categorised according to the level of exposure, and gradual infection control measures were applied. No clinical signs of Lassa virus infection or Lassa specific antibodies were observed in the 62 contacts. Thirty-three individuals had direct contact to blood, other body fluids or tissue of the patients. Notably, with standard precautions, no transmission occurred between the index patient and healthcare workers. However, one secondary infection occurred in an undertaker exposed to the corpse in Rhineland-Palatinate, who was treated on the isolation unit at the University Hospital of Frankfurt. After German authorities raised an alert regarding the imported Lassa fever case, an American healthcare worker who had cared for the index patient in Togo, and who presented with diarrhoea, vomiting and fever, was placed in isolation and medevacked to the United States. The event and the transmission of Lassa virus infection outside of Africa underlines the need for early diagnosis and use of adequate personal protection equipment (PPE), when highly contagious infections cannot be excluded. It also demonstrates that larger outbreaks can be prevented by infection control measures, including standard PPE

Bidentate Lewis Acid Catalyzed Inverse-Electron-Demand Diels-Alder Reaction for the Selective Functionalization of Aldehydes

The inverse-electron-demand Diels-Alder (IEDDA) reaction catalyzed by a bidentate Lewis acid was applied to enamines generated in situ from aldehydes. In general, a high functional group tolerance has been observed. Side reactions during the enamine forming step can limit the yield of the desired naphthalene. For citronellal as substrate, the initial intermediate after the catalyzed IEDDA reaction was trapped by an intramolecular Diels-Alder reaction to furnish a tricyclic compound. This scaffold represents the framework of natural products such as valerianoids A-C or the patchouli alcohol

Metallohosts with a heart of carbon

Single-crystal X-ray diffraction studies have confirmed that Ni3S3-based molecular bowls prepared in one-pot reactions capture either CH2Cl2 or C-60. The nature of the pendant substituents (naphthalen-2-ylmethyl, benzyl, or ethyl) around the rim of the bowl dictates the formation of a 1:1 (bowl host-C-60 guest) or 2:1 (capsule host-C-60 guest) architecture. In CDCl3, the trimeric complexes were found to be in equilibrium with dimeric analogues. For the naphthalen-2-ylmethyl-substituted host, NMR spectroscopic titration data confirmed a 1:1 host-C-60 guest complex in 1,2-Cl2C6D4 solution

Hydrogen-Bond and Solvent Dynamics in Transition Metal Complexes : a Combined Simulation and NMR-Investigation

Self-assembling ligands through complementary hydrogen-bonding in the coordination sphere of a transition metal provides catalysts with unique properties for carbon-carbon and carbon-heteroatom formation. Their most distinguishing chemical bonding pattern is a double-hydrogen-bonded motif, which determines much of the chemical functionality. Here, we discuss the possibility of double proton transfer (DPT) along this motif using computational and experimental methods. The infrared and NMR spectral signatures for the double-hydrogen-bonded motif are analyzed. Atomistic simulations and experiments suggest that the dynamics of the catalyst is surprisingly complex and displays at least three different dynamical regimes which can be distinguished with NMR spectroscopy and analyzed from computation. The two hydrogen bonds are kept intact and in rapid tautomeric exchange down to 125 K, which provides an estimate of 5 kcal/mol for the barrier for DPT. This is confirmed by the simulations which predict 5.8 kcal/mol for double proton transfer. A mechanistic interpretation is provided and the distribution of the solvent shell surrounding the catalyst is characterized from extensive simulations

Diastereoselective and Highly Enantioselective Henry Reactions using C(1)-Symmetrical Copper(II) Complexes

Catalytic Henry reactions of aliphatic aldehydes and prochiral nitro compounds were investigated using copper(II) complexes of 14 C(1)-symmetrical ligands derived from (1R,2R)(-)-diaminocyclohexane. beta-Nitro alcohols with syn:anti ratios of up to 5.7 and excellent ee values for both diastereosimers were obtained