gamma-Methoxy allylsulfonyl anions undergo smooth conjugate addition to mono- and bicyclic cyclopentyl sulfones. Hydrolysis of the intermediate abducts affords delta-sulfonyl-substituted enones which may be eliminated to dienyl ketones. The mechanism of this reaction is shown to involve the intermediacy of spiro-fused cyclopropyl sulfones conjugated to an enol ether moiety. Exploration of the scope and limitations of this procedure demonstrates the potential for triply-convergent synthesis of tricyclic dienones via cyclization of a trienyl ketone.