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.     

Eine Cyanogruppe als Dienophil in einer intramolekularen π4 + π2-Cycloaddition

At elevated temperatures the 11, 14-cycloadducts of tetracyanoethylene with esters of retinoic acid or with retinol acetate are transformed into 5,9-methano-2H-cyclohepta[b]-pyridines by intermolecular _π4 + _π2-cycloaddition of a cyano group followed by a double bond shift. The resulting structure was determined by x-ray analysis.