Fluorinated cyclohexanes: Synthesis of amine building blocks of the all- cis 2,3,5,6-tetrafluorocyclohexylamine motif

This paper reports the synthesis of three amine stereoisomers 5a–c of the tetrafluorocyclohexyl ring system, as building blocks for discovery chemistry programmes. The synthesis starts from a Birch reduction of benzonitrile, followed by an in situ methyl iodide quench. The resultant 2,5-cyclohexadiene was progressed via double epoxidations and then hydrofluorination ring opening reactions. The resultant fluorohydrin moieties were then converted to different stereoisomers of the tetrafluorocyclohexyl ring system, and then reductive hydrogenation of the nitrile delivered three amine stereoisomers. It proved necessary to place a methyl group on the cyclohexane ring in order to stabilise the compound against subsequent HF elimination. The two all-cis tetrafluorocyclohexyl isomers 5a and 5b constitute facially polarized cyclohexane rings, with fluorines on the electronegative face and hydrogens on the electropositive face

A Core Switching Strategy to Pyrrolo[2,3-b]quinolines and Diazocino[1,2-a]indolinones

Two novel core-switching rearrangements to natural product-like privileged scaffolds that proceed in up to 99% yield have been developed. The deviation away from planarity of the central N-acyl urea carbonyl, caused by the structure of the medium-sized ring, dictates the exclusive reaction outcome. Proposed mechanisms and products for the reaction pathways are supported by small molecule X-ray crystallography and an isolated intermediate. Twenty-four novel rearrangement products are reported

Ph Controlled Assembly of a Self-complementary Halogen-bonded Dimer

Phenols and their corresponding phenoxide anions can form halogen bonds with neutral iodotriazoles. The strength of these interactions depends critically on the protonation state of the oxygen atom – the interaction of the phenoxide anion is more than an order of magnitude stronger than the corresponding phenol. The assembly of a molecule bearing both an iodotriazole and a phenoxide anion into a self-complementary dimer, stabilised by two halogen bonds between the phenoxide anions and the neutral iodotriazoles has been demonstrated. The corresponding phenol shows no halogen bond mediated assembly either in the solid or in the solution state. This assembly process can be actuated simply by a change in protonation state – treatment of the phenol with one equivalent of base results in deprotonation and assembly of the dimer. The structure of the homodimer formed by the phenoxide-bearing iodotriazole has been determined in the solid state and 19F NMR spectroscopy demonstrates that the assembled dimer persists in solution and that it has significant stability. 19F NMR spectroscopy has also been used to demonstrate that the assembly process is completely reversible

A Deep-Blue-Emitting Heteroatom-Doped MR-TADF Nonacene for High-Performance Organic Light-Emitting Diodes

We present a p- and n-doped nonacene compound, NOBNacene, that represents a rare example of a linearly extended ladder-type multiresonant thermally activated delayed fluorescence (MR-TADF) emitter. This compound shows efficient narrow deep blue emission, with a λPL of 410 nm, full width at half maximum, FWHM, of 38 nm, photoluminescence quantum yield, ФPL of 71%, and a delayed lifetime, τd of 1.18 ms in 1.5 wt% TSPO1 thin film. The organic light-emitting diode (OLED) using this compound as the emitter shows a comparable electroluminescence spectrum peaked at 409 nm (FWHM = 37 nm) and a maximum external quantum efficiency (EQEmax) of 8.5% at Commission Internationale de l'Éclairage (CIE) coordinates of (0.173, 0.055). The EQEmax values were increased to 11.2% at 3 wt% doping of the emitter within the emissive layer of the device. At this concentration, the electroluminescence spectrum broadened slightly, leading to CIE coordinates of (0.176, 0.068)

The synthesis of gallium phosphte frameworks with and without fluoride ions present: attempts to direct the synthesis of double four ring-containing materials

During attempts to synthesise gallium phosphate materials containing the double four-ring building unit, three pyridine-templated gallium fluorophosphates and one pyridine-templated gallium phosphate were prepared and their structures solved using single crystal X-ray diffraction experiments. None of the three fluorophosphates contained the double four-ring unit, while the material prepared in the absence of fluoride did. This overturns some of the conventional wisdom that fluoride is necessary to specifically form the double four-ring unit. The synthetic conditions needed to prepare the materials and possible relationships between the building units found in the solids are discussed.</p