In contrast to previously reported borylative heterocyclization methods, a reaction here proceeds without air-free techniques to access synthetically useful borylated thiophenes, benzothiophenes, and isocoumarins. A comparison of stability/decomposition rates in air of several catecholboronic ester (Bcat) compounds derived from different heterocycle cores showed a strong dependence on the heterocycle structure. Lessons learned from this comparison were then harnessed for the development of borylative heterocyclization reactions under ambient-atmosphere conditions and with wet solvent. In contrast to literature reports suggesting general moisture sensitivity, a subset of Bcat products resulting from this technique were chromatography-stable and directly isolable, obviating the requirement for an extra synthetic transformation into more stable boron species, such as pinacolboronic esters (Bpin), for isolation. The isolated Bcat products were amenable to various downstream functionalization reactions, including reactions that were not accessible with their better-known Bpin counterparts, showing the complementarity of Bcat reaction partners and expanding their known chemistry. These results suggest the value of conceptual revisitation of substitution and solvent influence on stability and isolability of organo-Bcat compound classes and lay the groundwork for development of additional practical borylative methods in air.

Pheox– and Phebox–aluminum complexes were synthesized and subsequently characterized by spectroscopic analysis. These complexes acted as Lewis acid catalysts, and their catalytic activities were controlled by using the Pheox, Phebox, and heteroatom ligands. The Pheox–aluminum complex exhibited an opposite substrate selectivity to AlCl3 in a competitive hetero‐Diels–Alder reaction between electron‐rich and electron‐deficient aldehydes.

A coupling reaction of electron‐deficient alkenyl ethers with silyl enolates catalyzed by InBr3 was achieved. Various silyl enolates and 2‐carbonylalkenyl ethers were applicable, giving the corresponding 1,5‐dioxo‐alk‐2‐enes with perfect stereoselectivity of the alkene moieties. The present coupling reaction proceeds via the 1,4‐addition of silyl enolates to alkenyl ethers followed by elimination of silyl alkoxides, in which moderate‐Lewis acidic InBr3 performs both the activation of alkenyl ethers and the elimination of alkoxy groups regardless of the presence of various coordinative functional groups.

We revealed the effects of the substituents in ligands on properties of Phebox-aluminum complexes. The substituents at the 4-position of Phebox ligands effectively influenced the Lewis acidity via the conjugation between the vacant orbital on the Al atom and π* orbital of the benzene ring, which is supported by DFT calculation. The catalytic activity was also tuned, and a series of substituted Phebox-Al(ClO4)2 effectively catalyzed hydroboration of benzaldehyde. In addition, an unexpected photocatalytic activity of Phebox-Al complexes was found and applied to the hydrodebromination of a 4-bromo benzoic ester.

Development of an effective catalytic system for the cycloaddition of carbon dioxide to epoxides for the preparation of cyclic carbonates under mild conditions is of great importance. Herein, a mixture of zinc iodide, metal chlorides, and strong organic bases is demonstrated to be a useful catalytic system that works at room temperature under atmospheric pressure. The most efficient combination, zinc iodide-niobium chloride-7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (1.2-0.3-3.0 mol%), gave styrene carbonate (95%) from styrene oxide and CO2 (balloon) at 25 °C for 24 h. Another combination, zinc iodide-zinc chloride-1,8-diazabicyclo[5.4.0]undec-7-ene (1.2-0.8-4.0 mol%), kept the catalytic activity for the preparation of propylene carbonate until the fourth run. Therefore, the reaction system was operationally simple, highly efficient, and proceeded under ambient conditions. The catalyst is composed of readily available reagents and is reusable. Thus, the method presented is a powerful tool for utilizing CO2 as the starting material for the production of valuable chemicals.