Post-Formation of Fused Pentagonal Structure on Fjord Region of Polyaromatic Hydrocarbons under Hydrothermal Conditions

This study explores the synthesis of cyclopenta-fused polyaromatic hydrocarbons (CP-PAHs) via Pt-catalyzed cyclization in water, focusing on the formation of fused pentagonal rings within heavily fused PAH frameworks. Utilizing platinum catalysts at lower temperatures (200-260 °C) in water, led to the successful synthesis of singly cyclized CP-PAHs. The reaction conditions facilitated the mono-cyclization of substrates such as dibenzo[g,p]chrysene and its isomers, yielding the desired products while suppressing the formation of bis-cyclized compounds. The use of Fe2O3 as an additive in conjunction with PtO2 was effective to suppress hydrogenation of the substrates and products. The products exhibited a redshift in UV-visible absorption and photoluminescence bands due to a decrease in the HOMO-LUMO energy gap. These findings highlight the potential of Pt-catalyzed cyclization for the controlled synthesis of CP-PAHs, with implications for various applications in materials science.

Synthesis and Biological Evaluation of Enantiomerically Pure (R)- and (S)-[18F]OF-NB1 for Imaging the GluN2B Subunit-Containing NMDA Receptors

GluN2B subunit-containing N-methyl-d-aspartate (NMDA) receptors have been implicated in various neurological disorders. Nonetheless, a validated fluorine-18 labeled positron emission tomography (PET) ligand for GluN2B imaging in the living human brain is currently lacking. The aim of this study was to develop a novel synthetic approach that allows an enantiomerically pure radiosynthesis of the previously reported PET radioligands (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1 as well as to assess their in vitro and in vivo performance characteristics for imaging the GluN2B subunit-containing NMDA receptor in rodents. A novel synthetic approach was successfully developed, which allows for the enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1 and the translation of the probe to the clinic. While both enantiomers were selective over sigma2 receptors in vitro and in vivo, (R)-[18F]OF-NB1 showed superior GluN2B subunit specificity by in vitro autoradiography and higher volumes of distribution in the rodent brain by small animal PET studies.

Synthesis and Biological Evaluation of Enantiomerically Pure (R)- and (S)-[18F]OF-NB1 for Imaging the GluN2B Subunit-Containing NMDA receptors

GluN2B subunit-containing N-methyl-d-aspartate (NMDA) receptors have been implicated in various neurological disorders. Nonetheless, a validated fluorine-18 labeled positron emission tomography (PET) ligand for GluN2B imaging in the living human brain is currently lacking. As part of our PET ligand development program, we have recently reported on the preclinical evaluation of [18F]OF-NB1 - a GluN2B PET ligand with promising attributes for potential clinical translation. However, the further development of [18F]OF-NB1 is currently precluded by major limitations in the radiolabeling procedure. These limitations include the use of highly corrosive reactants and racemization during the radiosynthesis. As such, the aim of this study was to develop a synthetic approach that allows an enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1, as well as to assess their in vitro and in vivo performance characteristics for imaging the GluN2B subunit-containing NMDA receptor in rodents. A two-step radiosynthesis involving radiofluorination of the boronic acid pinacol ester, followed by coupling to the 3-benzazepine core structure via reductive amination was employed. The new synthetic approach yielded enantiomerically pure (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1, while concurrently circumventing the use of corrosive reactants. In vitro autoradiograms with mouse and rat brain sections revealed a higher selectivity of (R)-[18F]OF-NB1 over (S)-[18F]OFNB1 for GluN2B-rich brain regions. In concert with these observations, blockade studies with commercially available GluN2B antagonist, CP101606, showed a significant signal reduction, which was more pronounced for (R)-[18F]OF-NB1 than for (S)-[18F]OF-NB1. Conversely, blockade experiments with sigma2 ligand, FA10, did not result in a significant reduction of tracer binding for both enantiomers. PET imaging experiments with CD1 mice revealed a higher brain uptake and retention for (R)-[18F]OF-NB1, as assessed by visual inspection and volumes of distribution from Logan graphical analyses. In vivo blocking experiments with sigma2 ligand, FA10, did not result in a significant reduction of the brain signal for both enantiomers, thus corroborating the selectivity over sigma2 receptors. In conclusion, we have developed a novel synthetic approach that is suitable for upscale to human use and allows the enantiomerically pure radiosynthesis of (R)-[18F]OF-NB1 and (S)-[18F]OF-NB1. While both enantiomers were selective over sigma2 receptors in vitro and in vivo, (R)-[18F]OF-NB1 showed superior GluN2B subunit specificity by in vitro autoradiography and higher volumes of distribution in small animal PET studies.

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF3)2CHOH]

A facile synthesis of carbo- and heterohelicenes was achieved via tandem cycloaromatization of bisacetal precursors, which were readily prepared through C–C bond formation by Suzuki–Miyaura coupling. This cyclization was efficiently realized by a catalytic amount of trifluoromethanesulfonic acid (TfOH) in a cation-stabilizing solvent, 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), which readily allowed gram-scale syntheses of higher-order helicenes, double helical helicenes, and heterohelicenes.

Sequential Suzuki-Miyaura Coupling/Lewis Acid-Catalyzed Cyclization: An Entry to Functionalized Cycloalkane-Fused Naphthalenes

Functionalized angular cycloalkane-fused naphthalenes were prepared using a two-step process involving a Pd-catalyzed Suzuki-Miyaura coupling of aryl pinacol boronates and vinyl triflates followed by a boron trifluoride etherate-catalyzed cycloaromatization.

Brønsted acid-catalysed hydroarylation of unactivated alkynes in a fluoroalcohol–hydrocarbon biphasic system: construction of phenanthrene frameworks

Transition metal-free, Brønsted acid-catalysed hydroarylation of unactivated alkynes was achieved in a two-phase solvent system consisting of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) and cyclohexane.

N-Bromosuccinimide-Induced C-H Bond Functionalization: An Intramolecular Cycloaromatization of Electron Withdrawing Group Substituted 1-Biphenyl-2-ylethanone for the Synthesis of 10-Phenanthrenol

An NBS-induced intramolecular cycloaromatization for the synthesis of 10-phenanthrenols from electron-withdrawing group substituted 1-biphenyl-2-ylethanones is described. The in situ generated bromide was designed to act as an initiator for the radical C-H bond activation. An oxidative cross-dehydrogenative coupling reaction of a highly active C-H bond with an inert C-H bond readily occurs under mild conditions without the need for transition metals or strong oxidants.