Cycloaddition behavior of 3,4-diazacyclopentadienone dioxides toward bicyclo[2.2.1]heptadiene derivatives. X-ray analysis of the cycloadduct and reaction pathway
The cycloaddition behavior of 2,5-disubstituted 3,4-diazacyclopentadienone dioxide 1a-c toward epoxy-naphthalene (2a) and norbornadiene (2b) was investigated. The structures of the products were determined on the basis of the 1H- and 13C-nmr spectral data and the X-ray analysis data. The stereospecific formation of the endo-exo 1,3-dipolar cycloadducts from 2a indicates that the cycloadduct resulted
A new formation pathway via [3,3]-sigmatropic rearrangement of the 1,3-dipolar reaction product was proposed for the novel nitrogen-free compound formed from the reaction of 3,5-disubstituted 4-oxo-4H-pyrazole 1,2-dioxide with dimethylacetylenedicarboxylate.