Soft hydrogen bonds to alkenes: the methanol–ethene prototype under experimental and theoretical scrutiny

An FTIR spectroscopic study of the elusive hydrogen-bonded methanol–ethene complex, the most elementary example for weak intermolecular alcohol hydrogen bonding to a π cloud, is presented. By isolating the complex in a supersonic jet, the rigorous comparability to high-level quantum chemical calculations is ensured. In stark contrast to classical hydrogen bonds, experimental overtone analysis reveals the harmonic oscillator approximation for the OH red shift to be accurate. Harmonic calculations up to explicitly correlated local coupled-cluster level are thus found to agree very well with experiment. The experimental OH values for the red shift (45 cm^–1), the small change in diagonal anharmonicity (–3 cm^–1) and the overtone intensity attenuation (2 × 10²-fold) together with theoretical predictions for the preferred structural arrangement and the zero-point-corrected dissociation energy (8 kJ mol^–1) may thus be regarded as definitive reference values for related systems and for more approximate computational methods. In particular, MP2 calculations are shown to fail for this kind of weak intermolecular interaction.     

Enantioselective Approach for Expanding the Three-Dimensional Space of Tetrahydroquinoline to Develop BET Bromodomain Inhibitors**

The pharmaceutical industry has a pervasive need for chiral specific molecules with optimal affinity for their biological targets. However, the mass production of such compounds is currently limited by conventional chemical routes, that are costly and have an environmental impact. Here, we propose an easy access to obtain new tetrahydroquinolines, a motif found in many bioactive compounds, that is rapid and cost effective. Starting from simple raw materials, the procedure uses a proline-catalyzed Mannich reaction followed by the addition of BF₃ ⋅ OEt₂, which generates a highly electrophilic aza-ortho-quinone methide intermediate capable of reacting with different nucleophiles to form the diversely functionalized tetrahydroquinoline. Moreover, this enantioselective one-pot process provides access for the first time to tetrahydroquinolines with a cis-2,3 and trans-3,4 configuration. As proof of concept, we demonstrate that a three-step reaction sequence, from simple and inexpensive starting compounds and catalysts, can generate a BD2-selective BET bromodomain inhibitor with anti-inflammatory effect.     

Dual Gold‐Catalyzed Head‐to‐Tail Coupling of Iodoalkynes

Various haloalkynes are converted in the presence of a dual activation gold catalyst. Via a dual activation process a completely atom economic head‐to‐tail coupling delivers gem‐dihalogenated conjugated enynes as valuable building blocks for organic synthesis.     

Multicomponent Self‐Assembly with a Shape‐Persistent N‐Heterotriangulene Macrocycle on Au(111)

Multicomponent network formation by using a shape‐persistent macrocycle ( MC6 ) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning tunneling microscopy (STM) reveals the formation of crystalline bicomponent networks upon codeposition of MC6 with aromatic molecules, such as fullerene (C₆₀) and coronene. Tetracyanoquinodimethane, on the other hand, was found to induce disorder into the MC6 networks by adsorbing on the rim of the macrocycle. Immobilization of MC6 itself was studied in two different noncovalently assembled host networks. MC6 assumed a rather passive role as a guest and simply occupied the host cavities in one network, whereas it induced a structural transition in the other. Finally, the central cavity of MC6 was used to capture C₆₀ in a complex three‐component system. Precise immobilization of organic molecules at discrete locations within multicomponent networks, as demonstrated here, constitutes an important step towards bottom‐up fabrication of functional surface‐based nanostructures.     

Monotone operators on Gödel logic

We consider an extension of Gödel logic by a unary operator that enables the addition of non-negative reals to truth-values. Although its propositional fragment has a simple proof system, first-order validity is Π ₂-hard. We explain the close connection to Scarpellini’s result on Π ₂-hardness of ?ukasiewicz’s logic.     

Crystal structure of a butyllithium 1,2-dipiperidinoethane dimer complex

The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane as a centrosymmetric dimer in the monoclinic space group P2₁/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6 has a planar central Li₂C₂ core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified three structural motifs that affect Li₂C₂ dimer ring planarity.     

Synthesis and Crystal Structure of [Li(THF)<Subscript>4</Subscript>]Cu<Subscript>2</Subscript>Br<Subscript>4</Subscript>

The mixed-valence compound [Li(THF)₄]Cu₂Br₄ was synthesized in a redox reaction from 1,4-dihydroxynaphthalene, CuBr₂ and LiNtBuSiMe₃ in THF. X-ray quality crystals of [Li(THF)₄]Cu₂Br₄ (monoclinic, P2₁/c) are obtained from the mother liquor at ambient temperature. In the solid state, infinite chains of anionic [Cu₂Br₄]⁻ units are established. These chains are separated by [Li(THF)₄]⁺ cations.