Diademan und Strukturverwandte, I. Darstellung und charakteristische Reaktionen einiger Tris-σ-homobenzol-Kohlenwasserstoffe

Beyond the Dimer and Trimer: Tetraspiro[2.1.2(5).1.2(9).1.2(13).1(3)] hexadecane-1,3,5,7-tetraone--the Cyclic Tetramer of Carbonylcyclopropane

Tetraspiro[2.1.2(5).1.2(9).1.2(13).1(3)]hexadecane-1,3,5,7-tetraone 4, a unique tetraketone containing a cyclooctane core and four spiroannelated cyclopropane moieties, represents the previously unknown cyclotetramer of carbonylcyclopropane. For this purpose oxidation of the parent polyspirocyclic hydrocarbon was examined under various oxidative conditions, and the reactivity of oxidants towards methylene groups of the eight-membered cycle, activated by adjacent spirocyclopropane rings, was evaluated and contrasted. Whereas the treatment of tetraspirohexadecane with ozone resulted in monooxidation, its reaction with methyl(trifluoromethyl)dioxirane afforded the product of four-fold oxidation, triketoalcohol 10. Subsequent oxidation of the latter with Dess-Martin periodinane gave the target tetraketone 4.

From Fragmentation to Construction--from Void to Massive: Fascination with Organic Mass Spectrometry and the Synthesis of Novel Three-Dimensional Polycyclic Aromatic Hydrocarbons

Detailed insights gained from our research into the gas-phase chemistry of ionized and protonated diphenylalkanes and their congeners, obtained by extended synthesis of isotopically labeled model compounds and mass spectrometry, are presented and merged with those acquired during our development of a new family of polycyclic hydrocarbons, the centropolyindanes. Aside from a Personal Account that describes "two scientific lives in one", it is demonstrated, on the one hand, how our understanding of organic chemistry can help to shed light on the details of mass spectrometric fragmentation and to unravel, in a more fundamental way, the unimolecular reactivity of gaseous ions. On the other hand, it is shown how unexpected reactivity of related ions in solution, being subject to the very same fundamentals of organic chemistry, can lead to the construction of novel and, in part, unique three-dimensional polycyclic structures that may contribute to future research in material science. Two such apparently independent fields of organic chemistry may be seen as joint contributions of the art of science.

Palladium Catalyzed Cyclopropanation of Unsaturated Endoperoxides. A New Peroxide Preserving Reaction

Unsaturated bicyclic endoperoxides are efficiently cyclopropanated with excess diazomethane in the presence of catalytic Pd(OAc)₂ in a stereoselective manner. This method represents a new peroxide preserving transformation. Whereas the unsaturated endoperoxides in the [2.2.1] series are attacked by the carbene from the exo face, the analogs with larger bridges are preferentially attacked from the face syn to the peroxo bridge. Only in the case of the benzannelated [2.2.2] system the attack occurs exclusively from the face proximal to the benzene ring. Certain strained cyclopropanated endoperoxides are reduced by diazomethane to give cis-diols. 1-Methylfuran endoperoxide gives rise to cis-1-formyl-2-acetylcyclopropane in excellent yield.

Cahn-Ingold-Prelog descriptors of absolute configuration for carbon cages

A simplified procedure is described for assigning Cahn-Ingold-Prelog descriptors to stereocentres in spheroalkanes (the CnHn molecules, with n even, based on trivalent, polyhedral carbon frameworks, a class which subsumes the fulleranes). By extension, similar descriptors can be found for the atoms of fullerenes and related carbon-only molecules. Assignment maps are given for chiral fullerenes C28 C76, C78, C84 and C140, and for a number of spheroalkanes. Cases of breakdown of the simple procedure for triangle-rich spheroalkane molecular graphs are discussed.

Chirality and symmetry aspects of spheroarenes, including fullerenes

The design of the smallest spheroarenes (C(N) molecules based on trivalent polyhedral framework, a class which subsumes fullerenes) of any point-group symmetry is presented. The role of Curie's principle is discussed. Some molecules whose carbon backbone is a nonplanar graph are described.