Metal-free double azide addition to strained alkynes of an octadehydrodibenzo[12]annulene derivative with electron-withdrawing substituents

Strain-promoted azide-alkyne cycloaddition (SpAAC) is a powerful tool in the field of bioconjugation and materials research. We previously reported a regioselective double addition of organic azides to octadehydrodibenzo[12]annulene derivatives with electron-rich alkyloxy substituents. In order to increase the reaction rate, electron-withdrawing substituents were introduced into octadehydrodibenzo[12]annulene. In this report, the synthesis of new octadehydrodibenzo[12]annulene derivatives, regioselective double addition of organic azides, and an application to crosslinking polymers are described.

Clicking in harmony: exploring the bio-orthogonal overlap in click chemistry

In the quest to scrutinize and modify biological systems, the global research community has continued to explore bio-orthogonal click reactions, a set of reactions exclusively targeting non-native molecules within biological systems. These methodologies have brought about a paradigm shift, demonstrating the feasibility of artificial chemical reactions occurring on cellular surfaces, in the cell cytosol, or within the body - an accomplishment challenging to achieve with the majority of conventional chemical reactions. This review delves into the principles of bio-orthogonal click chemistry, contrasting metal-catalyzed and metal-free reactions of bio-orthogonal nature. It comprehensively explores mechanistic details and applications, highlighting the versatility and potential of this methodology in diverse scientific contexts, from cell labelling to biosensing and polymer synthesis. Researchers globally continue to advance this powerful tool for precise and selective manipulation of biomolecules in complex biological systems.

Synthesis and Characterization of Silyl[n]acediynes (Linearly Fused Benzodehydro[12]annulenes): Utilizing Bulkiness of Silyl Groups to Improve Selectivity

[n]Acediynes have unique properties owing to their highly strained and extended π-electron system. We have previously reported the selective synthesis of a silyl[1]acediyne, i.e., silyldibenzotetradehydro[12]annulene, utilizing the bulkiness of the silyl groups to improve the selectivity of the reaction. Herein, we report the facile synthesis of high-order silyl[n]acediynes via Eglington coupling between silyldiethynylbenzene and silyltetraethynylbenzene. In fact, silyl[2]acediyne as well as silyl[1]acediyne can be isolated from the reaction mixture. Their structures were determined using X-ray crystallography and discussed with reference to our previous report, and their spectroscopic properties, including absorption, fluorescence, Raman, and IR spectra, were fully characterized with DFT calculations. A drastic redshift in their absorption and fluorescence spectra occurred with an increase in the order number n of the [n]acediynes. The antiaromaticities of the dehydro[12]annulene moieties at the center of the annulene ring in these silylacediynes were also evaluated using NICS values. The calculated values were small and positive, which confirmed the weak antiaromatic character of the rings.