Au(I)-mediated N2-elimination from triazaphospholes: a one-pot synthesis of novel N2P2-heterocycles

Chemoselective Post-Synthesis Modification of Pyridyl-Substituted, Aromatic Phosphorus Heterocycles: Cationic Ligands for Coordination Chemistry

Triazaphospholes are potential polydentate ligands due to the presence of both phosphorus and nitrogen donor atoms within the aromatic 5-membered heterocycle. The incorporation of an additional pyridyl-substituent opens up the possibility of a post-synthesis modification via chemoselective and also stepwise alkylation exclusively of the nitrogen atoms. This can be controlled by the choice and by the stoichiometry of the electrophile and allows the targeted synthesis of a variety of novel mono- and dicationic ligands. Reaction with Cu(I)-halides causes the formation of cuprates of the type [CuXn](n-1)-, which enables coordination of the π-acidic phosphorus donor to the negatively charged metal core, which is favored over the coordination by a strongly σ-donating nitrogen atom. The use of cationic triazaphosphole derivatives can be used as a strategy to enforce the coordination of the ligand to an electron rich metal solely via the phosphorus atom. However, there is a subtle balance between the formation of either coordination polymers or dimeric structures, as the substitution pattern on the heterocycle and the nature of the halide have a large influence on the coordination motifs formed.

An Inorganic Click Reaction for the Synthesis of Interlocked Molecules

We describe the use of the cyaphide-azide 1,3-dipolar cycloaddition reaction for the synthesis of a new class of inorganic rotaxanes containing gold(I) triazaphosphole stoppers. Electron-deficient bis-azides, which thread perethylated pillar[5]arene in aromatic solvents, readily react with two equivalents of Au(IDipp)(CP) (IDipp=1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene) to afford interlocked molecules via an inorganic click reaction. These transformations proceed in good yields (ca. 65 %) and in the absence of a catalyst. The resulting organometallic rotaxanes are air- and moisture-stable and can be purified by column chromatography under aerobic conditions. The targeted rotaxanes were characterized by multi-element nuclear magnetic resonance (NMR) spectroscopy, mass-spectrometry, and single-crystal X-ray diffraction.

Reactions of main group compounds with azides forming organic nitrogen-containing species

Since the seminal discovery of phenyl azide by Grieß in 1864, a variety of organic azides (R-N3) have been developed and extensively studied. The amenability of azides to a number of reactions has expanded their utility as building blocks not only in organic synthesis but also in bioorthogonal chemistry and materials science. Over the decades, it has been demonstrated that the reactions of main group compounds with azides lead to diverse N-containing main group molecules. In view of the pronounced progress in this area, this review summarizes the reactions of main group compounds with azides, emphatically introducing their reaction patterns and mechanisms. The reactions of forming inorganic nitrogen species are not included in this review.

Luminescent Pyrrole‐Based Phosphaphenalene Gold Complexes: Versatile Anticancer Tools with Wide Applicability

Brain cancer, one of the most lethal diseases, urgently requires the discovery of novel theranostic agents. In this context, molecules based on six‐membered phosphorus heterocycles – phosphaphenalenes – are especially attractive; they possess unique characteristics that allow precise chemical engineering. Herein, we demonstrate that subtle structural modifications of the phosphaphenalene‐based gold(I) complexes lead to modify their electronic distribution, endow them with marked photophysical properties and enhance their efficacy against cancer. In particular, phosphaphenalene‐based gold(I) complexes containing a pyrrole ring show antiproliferative properties in 14 cell lines including glioblastomas, brain metastases, meningiomas, IDH‐mutant gliomas and head and neck cancers, reaching IC₅₀ values as low as 0.73 μM. The bioactivity of this new family of drugs in combination with their photophysical properties thus offer new research possibilities for both the fundamental investigation and treatment of brain cancer.

A new access to diazaphospholes via cycloaddition–cycloreversion reactions on triazaphospholes

The [4+2] cycloaddition of a triazaphosphole with hexafluoro-2-butyne, followed by a cycloreversion reaction under elimination of pivaloyl nitrile, affords selectively a novel bis-CF3-substituted diazaphosphole in high yield.