Conjugative effects in furan syn-diepoxides. Crystal and molecular structure of methyl 3,5,7-trioxatricyclo[4.1.0.0] heptane-1-carboxylate

Abstract

The stereochemistry of the title compound (2), a furan diepoxide derivative, has been defined in detail by means of an X-ray crystal structure analysis. Triclinic crystals in space group P have lattice parameters a= 4.1979(4), b= 13.948(1), c= 5.7324(4)Å, α= 92.462(7), β= 103.070(7), γ= 91.136(8)°, and Z= 2. The structure was solved by direct methods and refined by full-matrix least-squares calculations to R= 0.048 with 948 observed reflections. The two epoxy rings are in syn configuration, the five-membered ring is strictly planar and there are evidences of a π electron conjugation between the epoxy rings through a 2p orbital of the interconnecting oxygen atom. A suggestion for the interpretation of the reaction of crystal decay has been provided by the scrutiny of the difference electron density map.