Synthesis and acid- and base-promoted ring opening of polycarbocyclic oxiranes

Article abstract of DOI:10.1016/S0040-4020(98)00162-8

Acid promoted ring opening of 1α,4α,4aα,9aα-tetrahydro-2β-3β- epoxy-l,4-methanoanthracene-9,10-dione and the corresponding 2-methyl derivative (i.e., 3a and 3b, respectively) afforded 4a and 4b in 26% and 49% yield, respectively. Similar results were obtained when a solution of either 3a or 3b in aqueous acetone was reacted with Na₂CO₃ at ambient temperature for 2 days. However, reaction of 3b with aqueous methanolic NaOH (ambient temperature, 7 days) produced a small quantity of 4b along with a novel pentacyclic diketone, 6b (44% yield). Finally, acid promoted ring opening of 1α,4α-dihydro-4aα,9aα-epoxy- 1,4-methanoanthracene-9,10-dione (12) resulted in extensive skeltal rearrangement of the substrate, thereby affording 14 in low yield.