K 3 PO 4 -Promoted Cyclopropanation of Electron-deficient Alkenes with 2-Bromo-1,3-Propanedione Compounds

An easy and efficient method for the synthesis of multisubstituted cyclopropane derivatives from electron-deficicent alkenes with 2-bromo-1,3-propanedione compounds was described. For this method, ethyl α -cyanocinnamate derivatives 1 and β , β -dicyanostyrene derivatives 4 can all smoothly reacted with 2-bromo-1,3-propanedione compounds 2 to afford the corresponding multisubstituted cyclopropane derivatives 3 and 5 in good to excellent yields(up to 100%) promoted by anhydrous K 3 PO 4 in DMF at room temperature, respectively. A possible mechanism of this reaction was proposed. Structures of all the products were confirmed by 1 H NMR, 13 C NMR and HRMS.