Selective formation of spiro dihydrofurans and cyclopropanes through unexpected reaction of aldehydes with 1,3-dicarbonyl compounds.

An efficient methodology for the oxidative addition reaction of various aldehydes with 5,5-dimethylcyclohexane-1,3-dione and 1,3-indandione to selectively afford spiro dihydrofuran and cyclopropane derivatives, promoted by molecular iodine and dimethylaminopyridine under mechanical milling conditions, has been demonstrated. The products were obtained in good to excellent yields. A possible mechanism of this unusual reaction process is proposed.