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The article discusses the use of the inverse-electron-demand Diels-Alder (IEDDA) reaction as a synthetic tool for creating complex molecular structures. The authors focus on the use of bidentate Lewis acid catalysts to facilitate the IEDDA reaction between phthalazines and cyclooctynes. They found that the catalyst significantly increased the reaction rate and yield of the desired products. The authors also explored the scope of the reaction by testing different substituted phthalazines and cyclooctynes. The method presented in the article provides a convenient and efficient way to synthesize polycyclic aromatic hydrocarbons fused to eight-membered carbocycles. [Extracted from the article]

Herein we report the synthesis of nonsymmetrically substituted azobenzene derivatives with meta -alkyl substituents on one side and meta -aryl moieties with electron-donating or electron-withdrawing groups on the other side. The half-lives for the thermal (Z)- to (E)-isomerization of these molecules were measured in n -octane, which allows investigation of the strength of the aryl–alkyl interactions between their substituents. It was found that the London dispersion donor strength of the alkyl substrate is the decisive factor in the observed stabilization, whereas the electronic structure of the aryl fragment does not influence the isomerization in a significant way. [ABSTRACT FROM AUTHOR]

Azobenzenes have attracted increasing attention in the past years due to their application as molecular switches. In this report, we present a macrocyclic bisazobenzene that exists as the stable Z-isomer. The synthetic efforts as well as the successful strategy are discussed. Final ring closure under continuous irradiation gave the (Z,Z)-bisazobenzenophane. This Z-azobenzene does not show any isomerization under either heating or prolonged irradiation. The thermal stability of the Zform has also been supported by computations. The prepared bisazobenzenophane represents one of the few azobenzenes in which the Zisomer is more stable than the E-isomer. [ABSTRACT FROM AUTHOR]

This account describes synthetic approaches for curved polycyclic aromatics such as circulenes, helicenes and cycloparaphenylenes, relying on a [2+2+2] cycloaddition. A common feature of all these structures is that their synthesis needs to deviate benzene rings from planarity. Relying on [2+2+2] cycloaddition reactions for this task leads to impressive, and in parts, surprising results. The examples shown here and their optimized reaction conditions contribute to a better understanding of processes going on during the reaction. This knowledge is expected to lead to new designs of challenging syntheses using the [2+2+2] cycloaddition methodology. 1 No Gain, No Strain: Synthesis of Curved Aromatics 2 Examples for the Preparation of Strained Systems Relying on a [2+2+2] Cycloaddition 2.1 Circulenes 2.2 Helicenes 2.3 Cycloparaphenylenes 3 Conclusion and Outlook. [ABSTRACT FROM AUTHOR]

The inverse-electron-demand Diels-Alder (IEDDA) reaction catalyzed by a bidentate Lewis acid was applied to enamines generated in situ from aldehydes. In general, a high functional group tolerance has been observed. Side reactions during the enamine forming step can limit the yield of the desired naphthalene. For citronellal as substrate, the initial intermediate after the catalyzed IEDDA reaction was trapped by an intramolecular Diels- Alder reaction to furnish a tricyclic compound. This scaffold represents the framework of natural products such as valerianoids A-C or the patchouli alcohol. [ABSTRACT FROM AUTHOR]

A new concept for the catalysis of the inverse-electrondemand Diels-Alder (IEDDA) reaction of 1,2-diazenes using bidentate Lewis acid was recently reported by our group. The general catalytic principle is based on the simultaneous coordination of the bidentate Lewis acid to the 1,2-diazene moiety, lowering the LUMO to facilitate the cycloaddition step. Extrusion of N2 regenerates the catalyst and after elimination the aromatic product is obtained. In this account the development of this new catalytic principle is described and put into the general context of Lewis acid catalysis. [ABSTRACT FROM AUTHOR]