A Diels-Alder Approach to Potential Precursors of Polyhydroxylated Dihydroagarofurans­: A Ring-Opening/Ring-Closing Rearrangement

Abstract

Reduction of the Diels-Alder product from 2-methoxycarbonyl-1,4-benzoquinone and 1,3-dimethoxybuta-1,3-diene gave a dihydroxyenol ether which rearranged to a bicyclo[2.2.2]octenone on treatment with acid; in EtOH, intramolecular acetal formation without rearrangement was observed.

acetals - Diels-Alder reactions - rearrangements - stereoselective synthesis - terpenoids

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Crystal Data for 8: C₁₃H₁₆O₅, M = 252.27, orthorhombic, a = 9.496(3), b = 13.603(6), c = 9.464(3) Å, U = 1222.4(6) ų, T = 295(1) °C, space group P2₁2₁2₁ (no. 19), Z = 4, µ(CuKα) = 0.841 mm^-1, 1099 unique reflections, 1039 reflections with I > 3.00 σ(I) were used in the final refinement. Final R(F) = 0.0440. X-ray data have been submitted to the Cambridge Crystallographic Data Centre, CCDC number 281520.