Inverse‐electron demand [π2 + σ2 + σ2] cycloaddition reaction of dimethyl oxaquadricyclane‐2,3‐dicarboxylate with cyclooctyne

A first example of an inverse‐electron demand [_π2 + _σ2 + _σ2] cycloaddition reaction of dimethyl oxaquadricyclane‐2,3‐dicarboxylate was reported: cyclooctyne underwent cycloaddition with dimethyl oxaquadricyclane‐2,3‐dicarboxylate to afford the corresponding adducts one of whose structure was confirmed by a single crystal X‐ray analysis.     

The σ‐Aromatic Clusters [Zn3]+ and [Zn2Cu]: Embryonic Brass

The triangular clusters [Zn₃Cp*₃]⁺ and [Zn₂CuCp*₃] were obtained by addition of the in situ generated, electrophilic, and isolobal species [ZnCp*]⁺ and [CuCp*] to Carmona’s compound, [Cp*Zn? ZnCp*], without splitting the Zn? Zn bond. The choice of non‐coordinating fluoroaromatic solvents was crucial. The bonding situations of the all‐hydrocarbon‐ligand‐protected clusters were investigated by quantum chemical calculations revealing a high degree of σ‐aromaticity similar to the triatomic hydrogen ion [H₃]⁺. The new species serve as molecular building units of Cu_nZn_m nanobrass clusters as indicated by LIFDI mass spectrometry.     

Nanomagnetically modified thioglycolic acid (γ‐Fe2O3@SiO2‐SCH2CO2H): Efficient and reusable green catalyst for the one‐pot domino synthesis of spiro[benzo[a]benzo[6,7]chromeno[2,3‐c]phenazine] and benzo[a]benzo[6,7]chromeno[2,3‐c]phenazines

Superparamagnetic nanoparticles of modified thioglycolic acid (γ‐Fe₂O₃@SiO₂‐SCH₂CO₂H) represent a new, efficient and green catalyst for the one‐pot synthesis of novel spiro[benzo[a ]benzo[6,7]chromeno[2,3‐c ]phenazine] derivatives via domino Knoevenagel–Michael–cyclization reaction of 2‐hydroxynaphthalene‐1,4‐dione, benzene‐1,2‐diamines, ninhydrin and isatin. This novel magnetic organocatalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least six times without significant loss in its activity. The catalyst was fully characterized using various techniques. This procedure was also applied successfully for the synthesis of benzo[a ]benzo[6,7]chromeno[2,3‐c ]phenazines.