Calcium-Catalyzed Dynamic Multicomponent Reaction

The reversible formation of covalent bonds enabled by the remarkably high Lewis acidity of our calcium-based catalyst system was used for the development of a new type of multicomponent reaction. Accordingly, a pharmacologically interesting bicyclic amine was amplified from a highly efficient dynamic equilibrium. The product is formed with full diastereoselectivity, and as typical for our calcium-catalyzed reactions, precautions for the exclusion of air and moisture are unnecessary

The Alkynyl Moiety as a Donor for Donor–Acceptor Cyclopropanes

The first <i>trans</i>-selective [3 + 2]-cycloaddition of a new type of donor–acceptor cyclopropane with aldehydes is presented. 2,2-Disubstituted cyclopropanes, bearing an alkyne moiety as the sole donor entity, were transformed to highly substituted tetrahydrofurans in the presence of a catalytic amount of Ca(NTf₂)₂/Bu₄NPF₆. The protocol allows for an easy access to tetrahydrofurans bearing a versatile alkyne substituent at the quarternary 2-position under very mild reaction conditions

Diastereoselective Synthesis of Indanes and Tetralins via Intramolecular Friedel–Crafts Reaction

An easy access to tetralin and indane skeletons has been developed using a diastereoselective intramolecular Friedel–Crafts alkylation. Treatment of diastereomeric mixtures of benzyl carbinols with a catalytic amount of Ca(NTf₂)₂/Bu₄NPF₆ yields the respective tetralin or indane in good yields with high levels of regio- and diastereoselectivity