Bicyclo[1.1.1]pentanes (BCPs) have sparked the interest of medicinal chemists due to their recent discovery as bioisosteres of aromatic rings.T os tudy the biological activity of this relatively new class of bioisosteres,r eliable methods to incorporate BCPs into target molecules are in high demand, as reflected by af lurry of methods for BCP synthesis in recent years.I nt his work, we disclose ag eneral method for the synthesis of BCP-containing dithianes which,u pon deprotection, provide access to BCP analogues of medicinally abundant diarylketones.Abroad scope of 2-aryl-1,3-dithianes,including several heterocyclic derivatives,react with [1.1.1]propellane to afford2 6n ew derivatives in good to excellent yields.F urther transformation of the dithiane portion into av ariety of functional groups demonstrates the robustness of the products. Acomputational study indicates that the reaction of 2-aryl-1,3dithianes and [1.1.1]propellane proceeds via at wo-electron pathway.Scheme 1. Previous synthesis of BCP ketones, examples of bioactive diaryl ketones, general reactivity of dithianes, and synthesis of BCP dithianes.
Triphenyleneethynylene (TPEE) derivatives bearing one long aliphatic chain on each terminal aryl ring and two short aliphatic chains on the central aryl ring (core chains) self-assemble single component and 1-D patterned, two-component, crystalline monolayers at the solution-graphite interface. The monolayer morphology directs the core chains off the graphite, making them accessible for chemical reactions but invisible to imaging by scanning tunneling microscopy (STM). This precludes using STM to monitor transformations of the core chains, either by reaction or solution-monolayer exchange of TPEE molecules. Laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) successfully identifies TPEE compounds within physisorbed monolayers. The LDI-TOF spectra of TPEE monolayer-graphite samples exhibit strong molecular ion peaks and minimal fragmentation or background. LDI-TOF and STM techniques are combined to evaluate monolayer composition and morphology, track solution-monolayer exchange, to identify reaction products and to measure kinetics of chemical reactions at the solution-monolayer interface. LDI-TOF MS provides rapid qualitative evaluation of monolayer composition across a graphite substrate. Challenges to quantitative composition evaluation by LDI-TOF include compound-specific light absorption, surface desorption/ionization and fragmentation characteristics. For some, but not all, compounds, applying matrix onto a self-assembled monolayer increases molecular ion intensities and affords more accurate assessment of monolayer composition via matrix assisted laser desorption/ionization (MALDI) MS. Matrix addition precludes subsequent chemical or STM studies of the monolayer, whereas reactions and STM may be performed at nonirradiated regions following LDI-TOF measurements. LDI- and MALDI-TOF MS are useful complements to STM and are easily implemented tools for study of physisorbed monolayers.
We report a 3-component reaction between N-benzyl ketimines, [1.1.1]propellane, and pinacol boronates to generate benzylamine bicyclo[1.1.1]pentane (BCP) pinacol boronates. These structures are analogous to highly sought after diarylmethanamine cores, which...
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