'L dicarbonyl structures by intermolecular coupling is not possible using classical synthetic reactions, and consequently indirect approaches have been required, eg, a sequence employing the conjugate addition of nitrostabilized carbanions to enones. The reaction of conjugated enones with 2-lithio-1, 3-dithianes, which are synthetically equivalent to C- nucleophilic carbonyl group^,^ leads only to 1, 2 addition to the enone~ ystem,~ and other ...
