Synthesis and reactivity of Michael adducts of cyclic β-ketoesters enolates with electrophilic acetylenes

The enolates of cyclic β-ketoesters react with electrophilic acetylenes to give the corresponding Michael adducts in good yields when the reaction is performed in acetone in the presence of catalytic amounts of K2CO3. The Michael adducts resulting from ethynylmethylketone, when refluxed in toluene in the presence of catalytic amounts of pTsOH, undergo an intramolecular aldol reaction leading mainly to bicyclo [n. 3. 1]alkadienones besides Robinson annulation products.