A belt-shaped [8]­cycloparaphenylene (CPP) and an enantioenriched Möbius-shaped [10]­CPP have been synthesized by high-yielding rhodium-catalyzed intramolecular cyclotrimerizations of a cyclic dodecayne and a pentadecayne, respectively. This Möbius-shaped [10]­CPP possesses stable chirality and isolated with high enantiomeric purity. It is evident from the reaction Gibbs energy calculation that the above irreversible cyclotrimerizations are highly exothermic; therefore establishing that the intramolecular alkyne cyclotrimerization is a powerful route to strained cyclic molecular strips.

Terpene cyclization is orchestrated by terpene cyclases, which are involved in the biosynthesis of various cyclic natural products, but understanding the origin and mechanism of the selectivity of terpene cyclization is challenging. In this work, we describe an in-depth mechanistic study on cyclooctatin biosynthesis by means of theoretical calculations combined with experimental methods. We show that the main framework of cyclooctatin is formed through domino-type carbocation transportation along the terpene chain, which we call a “cation-stitching cascade”, including multiple hydrogen-shifts and a ring rearrangement that elegantly determine the stereoselectivity.

Diatomic carbon (C 2) is historically an elusive chemical species. It has long been believed that the generation of C 2 requires extremely high physical energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C 2 in the ground state is experimentally inaccessible. Here, we present the chemical synthesis of C 2 from a hypervalent alkynyl-λ 3-iodane in a flask at room temperature or below, providing experimental evidence to support theoretical predictions that C 2 has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that C 2 serves as a molecular element in the bottom-up chemical synthesis of nanocarbons such as graphite, carbon nanotubes, and C 60 .

The balance between the ring-walking process and the oxidative-addition state are key determinants of catalyst mobility in catalyst-transfer condensation polymerization.