A new approach to rethrolone synthesis

Abstract

Rearrangement of the 4-ylidenebutenolides (4) and (5), with sodium methoxide in methanol, leads to the cyclopent-2-ene-1,4-diones (6), which when heated with sodium chloride in dimethyl sulphoxide give the 1,4-diones (7). The latter can be reduced using zinc in acetic acid, to the dihydrorethrolones (8). In a similar manner, rearrangement of (10) produces (11a) which can be demethoxycarbonylated to (11b), an intermediate used previously in a synthesis of natural jasmololone (8; R = EtCH:CH).