A Novel and Facile Synthesis of Functionalized [4.4.3] and [4.4.4]Propellano-bislactones Using Acetates of the Baylis−Hillman Adducts

[reaction--see text] A simple and convenient synthesis of 11,16-di[(E)-arylidene]-13,14-dioxatetracyclo-[7.4.4.0.(1,9)0(2,7)]heptadeca-2,4,6-triene-12,15-diones and 12,17-di[(E)-benzylidene]-14,15-dioxatetracyclo[8.4.4.0.(1,10)0(2,7)]octadeca-2,4,6-triene-13,16-dione, i.e., 2,10-dioxa[4.4.3]propellane-3,9-diones and 2,10-dioxa[4.4.4]propellane-3,9-dione, using acetates of the Baylis-Hillman adducts has been described.