An efficient synthesis of 5,5-spiroketals (i.e., 1,6-dioxaspiro[4.4]nonane
derivatives) is described from 2-(sulfonimidoylmethylene)tetrahydrofurans
involving a consecutive epoxide opening/oxa-Michael spiroketalization
sequence. This methodology was applied to the very direct synthesis
of chalcogran, a beetle pheromone.
sulfoximine - 5,5-spiroketals - consecutive
reaction - chalcogran