Literature reports describe tetraethynylethylene (TEE) as unstable but tetravinylethylene (TVE) as stable. The stabilities of these two known compounds are reinvestigated, along with those of five unprecedented TEE-TVE hybrid compounds. The five new C10 hydrocarbons possess a core, tetrasubstituted CC bond carrying all possible combinations of vinyl and ethynyl groups. A unified strategy is described for their synthesis, whereupon cross-conjugated ketones are dibromo-olefinated then cross-coupled. Due to an incorrect but nonetheless widely held belief that acyclic π-bond rich hydrocarbons are inherently unstable, a standardized set of robustness tests is introduced. Whereas only TVE survives storage in neat form, all seven hydrocarbons are remarkably robust in dilute solution, generally surviving exposure to moderate heat, light, air, and acid. The first X-ray crystal structure of TEE is reported. Subgroups of hybrids based upon conformational preferences are identified through electronic absorption spectra and associated computational studies. These new acyclic π-bond rich systems have extensive, untapped potential for the production of stable, conjugated carbon-rich materials.

The first general synthesis of compounds of the tetravinylethylene (TVE) family is reported. Ramirez‐type dibromo‐olefination of readily accessible penta‐1,4‐dien‐3‐ones generates 3,3‐dibromo[3]dendralenes, which undergo twofold Negishi, Suzuki–Miyaura or Mizoroki–Heck reactions with a wide variety of olefinic coupling partners. This route delivers a broad range of unsymmetrically substituted tetravinylethylenes with up to three different alkenyl substituents attached to the central C=C bond. The extensive scope of the approach is demonstrated by the preparation of the first higher order oligo‐alkenic through‐conjugated/cross‐conjugated hybrid compounds. An unsymmetrically substituted TVE is shown to undergo a domino electrocyclization–cycloaddition with high site‐selectivity and diastereoselectivity, thereby demonstrating the substantial synthetic potential of substituted TVEs for controlled, rapid structural complexity generation.

A general synthetic approach to molecular structures that are hybrids of tetraethynylethylene (TEE) and tetravinylethylene (TVE) is reported. The synthesis permits the controlled preparation of many previously inaccessible structures, including examples with different substituents on each of the four branching arms. Most substituted TVE−TEE hybrids are found to be significantly more robust compounds than their unsubstituted counterparts, enhancing the prospects of their deployment in conducting materials and devices. Their participation in pericyclic reaction cascades, leading to sp 3 -rich polycycles, is demonstrated. The utilization of TEE−TVE hybrids as building blocks for larger acyclic, through/cross-conjugated hydrocarbon frameworks is also established. Aryl-substituted TEEs, TVEs, and their hybrids are fluorescent, with some exhibiting aggregation-induced emission enhancement. The structural requirements are defined and explained, setting the scene for applications as fluorescent probes and organic light-emitting diodes.

Die Titelverbindungen (VI) werden als Nebenprodukte bei der Synthese von (XII) und (XIV) erhalten.

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