Chiral acid catalysts are useful for the synthesis of enantioenriched small molecules, but the standard catalysts require laborious and expensive preparations. Here, we describe a chiral Brønsted acid prepared in one step from naturally occurring (-)-menthol and readily available 1,2,3,4,5-pentacarbomethoxycyclopentadiene. Aromatic stabilization serves as a key contributing factor to the potent acidity of the resulting compound, which is shown to catalyze both Mukaiyama-Mannich and oxocarbenium aldol reactions with high efficiency and enantioselectivity. Catalyst loadings as low as 0.01 mole percent and preparative scalability (25 grams) are demonstrated. Alternative amide catalysts are also shown to be promising platforms. In addition to proton catalysis, a chiral anion pathway is demonstrated to be viable with this catalyst system.

Ion transport in polymerized ionic liquids (poly-ILs) occurs via a fundamentally different mechanism than in monomeric ionic liquids, and recently progress has been made toward understanding ion conduction in poly-ILs. To gain insight into the nature of ionic conductivity in ionic polymers, we investigate the physical properties of the trisaminocyclopropenium (TAC) ion, as it is an aromatic carbocation with unique structural and electronic properties. Herein, we characterize the thermal properties, local morphology, and dielectric response of a series of monomeric and polymeric TAC ionic liquids with different counterions. We have found that the extent of a "superionic" mechanism depends on the nature of the ion pair and can result in anomalously high conductivity at the calorimetric T g . Our results suggest that the molecular volumes of the cationic and anionic species are important parameters that impact ion conductivity in polymerized ionic liquids.

An enantioselective catalytic inverse-electron-demand Diels-Alder reaction of salicylaldehyde acetal-derived oxocarbenium ions and vinyl ethers to generate 2,4-dioxychromanes is described. Chiral pentacarboxycyclopentadiene (PCCP) acids are found to be effective for a variety of substrates. Computational and X-ray crystallographic analyses support the unique hypothesis that an anion with point-chirality-induced helical chirality dictates the absolute sense of stereochemistry in this reaction.

Protocols for the synthesis of diverse PCCPs are described. Starting from readily available pentacarbomethoxycyclopentadiene, transesterification offers single-step access to aliphatic ester derivatives, while treatment with amines produces mono- or diamides. For less nucleophilic alcohols, an alternative procedure involving the in situ generation and esterification of a putative cyclopentadiene penta-acid chloride has been developed.

Aryl pyrimidones are pharmacologically relevant compounds whose optical properties have only been partially explored. We report the synthesis and optical characterization of a series of aryl- and diaryl-2(1H)-pyrimidones. The electronic transitions of these chromophores are modulated by the extent of conjugation between the pendant phenyl ring and the pyrimidone core as well as the presence of electron-donating auxochromes. Monoprotonation of the pyrimidone ring results in large hyperchromic and bathochromic shifts as well as switching of fluorescence making these phenyl pyrimidones of interest as sensory materials.