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Toward a conversion of aldehydes into arenes, we designed a sequence involving the initial reaction of an aldehyde to give a fulvene, followed by photochemical and platinum‐catalyzed rearrangements into a Dewar benzene derivative, which finally isomerizes into the targeted arene. While computational studies support the plausibility of this route, we found that fulvene irradiation resulted in an unexpected isomerization into a spiro[2.4]heptadiene. This unusual photorearrangement has been investigated mechanistically and provides access to a variety of spiro[2.4]heptadienes with different substituents. [ABSTRACT FROM AUTHOR]

Cumulenes have attracted considerable attention due to their unique structural and electronic properties. Despite their high potential for constructing condensed π‐conjugated molecules, the synthetic utility of longer cumulenes remains to be established owing to their inherently high reactivity. Conjugated bisbutatrienes having two cumulene moieties linked by a spacer as a mimic of a longer cumulene were evaluated. Here, the synthesis and characterization of hexafluorocyclopentane‐bridged bisbutatrienes are described. These bisbutatrienes underwent various cyclizations, to construct the unique π‐extended frameworks inaccessible by other methodologies. The bisbutatrienes were converted into fulvenes, pentalene, germacycle, and benzocyclobutene under various conditions. Furthermore, a cyclooctatetraene derivative was synthesized by a one‐step dimerization of the bisbutatriene. [ABSTRACT FROM AUTHOR]

We report di- and trinuclear palladium sandwich complexes of cross-π-conjugated fulvenes. Structural and theoretical analysis revealed that a fulvene sandwich framework holds a metal–metal bonded moiety, where the dinuclear and trinuclear bonds feature strong donation and back-donation, respectively. The trinuclear fulvene sandwich complex undergoes a unique reversible extrusion of a Pd atom from inside to outside the sandwich framework. [ABSTRACT FROM AUTHOR]

An efficient [4+2] cycloaddition reaction of fulvenes with aza-o-quinone methides, generated in situ from N -(o -chloromethyl)aryl sulfonamides with the assistance of a base, has been developed to afford a series of tetrahydroquinoline derivatives. The reaction tolerates a wide range of aza- o -quinone methides and fulvenes bearing four- to seven-membered rings to afford the corresponding tetrahydroquinolines in moderate to good yields. Based on a literature analysis, a plausible mechanism for this [4+2] cycloaddition is proposed. [ABSTRACT FROM AUTHOR]

• Study of photochemical behavior of di(cymantrenylalkyl)disulfide. • Preparation of stable bicyclic dicarbonyl chelates. • Preparation in situ of unstable fulvenes. • Study electrochemical properties of symmetrical disulfides. Photolysis of di(cymantrenylalkyl)disulfides was studied by IR, 1H NMR and UV-vis spectroscopy. Irradiation of cymantrenes with a disulfide bridge results in the formation of two type dicarbonyl chelates with Mn-S bond. The first type is formed due to removal of one CO ligand from one cymantrenyl moiety to give a 5-membered chelate cycle; the other is formed due to removal of two CO ligands from two cymantrenyl moieties to form a bicyclic chelate. The latter was isolated and characterized by X-ray analysis. For the first time, unstable fulvenes were prepared in situ by irradiation of cymantrenyl derivatives or their dicarbonyl complexes. Electrochemical properties of disulfides were studied before and after photolysis in acetonitrile. The manganese oxidation potential value increased on going from tricarbonyls to dicarbonyls. [Display omitted] [ABSTRACT FROM AUTHOR]