Crystal and molecular structures of methyl 2α,3α;4α,5α-diepoxy-cis-(1αH,2αH)-bicyclo[4.1.0]heptane-7α-carboxylate and methyl 2,5-dihydroxybicyclo[4.1.0]heptane-7-carboxylate

Abstract

X-Ray crystal analysis has been used to identify one isomer (III) of the two products C₉H₁₀O₄{methyl 2,5-epidioxybicyclo[4.1.0]hept-3-ene-7-carboxylate (II) and methyl 2α,3α:4α,5α-diepoxy-cis(1αH,2αH)-bicyclo[4.1.0]heptane-7α-carboxylate (III)} produced by the photosensitized oxygenation of methyl cyclohepta-2,4,6-trienecarboxylate (I). Crystals of (III) are orthorhombic, space group P2₁2₁2₁, with a= 19.548(1), b= 6.0101 (5), and c= 7.3944(4)Å and Z= 4. By hydrogenation of (II), methyl 2,5-dihydroxybicyclo[4.1.0]heptane-7carboxylate (V) is formed which also crystallizes in space group P2₁2₁2₁ with Z= 4, and cell dimensions a= 18.192(1), b= 7.7284(5), and c= 6.7139(3)Å. The structures were solved by the tangent formula phasing method and refined by full-matrix least-squares to R 0.055 (962 observed reflections) and 0.044 (1 028 observed reflections) respectively.

Compound (III) contains a six-membered ring consisting two planar fragments oriented at 3.4° to each other. The epoxide groups are tilted 108.0 and 105.6° from the plane through the four carbon atoms they include. In compound (V), two C–O bonds are broken, allowing the six-membered ring to assume the half-chair conformation. The cyclopropyl ring is inclined at 107.1 (III) and 109.0°(V) to the best plane through the two included and two adjacent carbon atoms. In both compounds, the carbonyl oxygen is located directly behind the cyclopropyl ring.