Cycloadditions between carbonyl oxides and dicarbonyl compounds: Isolation and characterisation of novel polycyclic 1,2,4,6-tetroxepane derivatives

Formaldehyde O-oxide reacts with dicarbonyl compounds to produce mono-ozonides formed by conventional [3 + 2] cycloadditions to an aldehydic carbonyl group of the substrate, and/or polycyclic 1,2,4,6-tetroxepane derivatives arising from formal [3 + 2 + 2] cycloadditions involving both carbonyl groups. Similar reactions between the more highly substituted carbonyl oxides, benzaldehyde and octanal O-oxides, and dicarbonyl compounds yielded the corresponding mono-ozonides as the sole isolable cycloaddition products. In certain favourable cases, mono-ozonides could undergo acid-catalysed intramolecular rearrangement to the corresponding 1,2,4,6-tetroxepanes. X- Ray crystallographic analyses of two 1,2,4,6-tetroxepanes. 6a and 13b, are recorded.