Synthesis of Bis-spiro Cyclopropanes Based on Meldrum's Acid by Milling

Reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid) with various solid aldehydes in the presence of cyanogen bromide and solid sodium ethoxide (EtONa) leads to the selective and efficient formation of bis-spiro cyclopropanes based on Meldrum's acid at the range of 0 degrees C to room temperature. The products were obtained in good to excellent yields. Structure elucidation is carried out by H-1 NMR, C-13 NMR, FT-IR spectroscopy, mass analyses and X-ray crystallography techniques. A possible mechanism for the formation of products is also discussed under solvent-free condition.