Regio- and stereoselective base-catalyzed assembly of 6-methylene-5-oxaspiro[2.4]heptanones from alkynyl cyclopropyl ketones.

6-Methylene-5-oxaspiro[2.4]heptanones have been synthesized base-catalyzed dimerization of available alkynyl cyclopropyl ketones. The reaction proceeds effectively in the presence of the -BuOK/-BuOH/THF catalytic system at room temperature to afford the desired spirocycles in a regio- and stereoselective manner.