Skeletal Modification of 1,2-Benzoquinone Monoximes into Conjugated ( <i>Z</i> , <i>Z</i> )-Dienes and 2-Cyanocyclopentadienones by Ring-Opening and Ring Contraction

A new strategy for stepwise dearomative functionalization of catechols is presented. The key substrates, 1,2-benzoquinone monoximes derived from readily available catechols, could be converted to conjugated (<i>Z</i>,<i>Z</i>)-dienes and 2-cyanocyclopentadienones. This divergent synthesis was enabled through either trapping the acylium intermediates, which were generated by C-C bond cleavage of 1,2-benzoquinone monoximes, with nucleophiles or a subsequent intramolecular Friedel-Crafts acylation. Further transformations of previously unknown dearomatized products were then delineated.