Organocatalytic Trapping of Elusive Carbon Dioxide based Heterocycles through a Kinetically Controlled Cascade Process

A conceptually novel approach is described for thesynthesis of larger-ring cyclic carbonates derived from carbon dioxide. The approach utilizes homoallylic precursors that are converted into five-membered cyclic carbonates having a beta-positioned alcohol group in one of the ring substituents. The activation of the pendent alcohol group through an N-heterocyclic base allows for equilibration towards a thermodynamically disfavored six-membered carbonate analogue that can be conveniently trapped by an acylation agent. Various control experiments and computational analysis of this manifold are in line with a process that is primarily dictated by a kinetically controlled acylation step. This cascade process delivers an ample diversity of novel six-membered cyclic carbonates in excellent yields and chemoselectivities under remarkably mild reaction conditions. This newly developed protocol helps to expand the repertoire of CO2-based heterocycles that are otherwise difficult to generate by conventional approaches.</div

Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes

Despite their inherent instability, 4n pi-systems have recently received significant attention due to their unique optical and electronic properties. In dibenzopentalene, benzanellation stabilizes the highly antiaromatic pentalene core, without compromising its amphoteric redox behavior or small HOMO–LUMO energy gap. However, incorporating such molecules in organic devices as discrete small molecules or ill-defined amorphous polymers can limit the performance (e.g. due to solubility in the electrolyte solution or low internal surface area). Covalent organic frameworks, on the contrary, are highly ordered, porous, and crystalline materials that can provide a platform to align molecules with specific properties in a well-defined, ordered environment. We synthesized the first antiaromatic framework materials and obtained a series of three highly crystalline and porous covalent organic frameworks based on dibenzopentalene. Potential applications of such antiaromatic bulk materials were explored: COF films show a conductivity of 4 × 10^(−8) S cm^(−1) upon doping and exhibit photoconductivity upon irradiation with visible light. Investigations as battery electrode materials demonstrate their ambipolar nature and the ability to store both anions and Li ions with enhanced charge storage capabilities compared to an aromatic COF or the conductive carbon material. This work showcases antiaromaticity as a new design principle for functional framework materials

Direct Regioselective Synthesis of Tetrazolium Salts by Activation of Secondary Amides under Mild Conditions

Tetrazolium salts are biologically active molecules that have found broad applications in biochemical assays. A regioselective synthesis of tetrazolium salts is described through a formal (3 + 2) cycloaddition. The possibility of employing simple amides and azides as starting material and the mild conditions allow a broad functional group tolerance

Direct Regioselective Synthesis of Tetrazolium Salts by Activation of Secondary Amides under Mild Conditions

Tetrazolium salts are biologically active molecules that have found broad applications in biochemical assays. A regioselective synthesis of tetrazolium salts is described through a formal (3 + 2) cycloaddition. The possibility of employing simple amides and azides as starting material and the mild conditions allow a broad functional group tolerance