Regio- and Stereoselective Synthesis of Cyclobutanes by Nickel-Catalyzed Homodimerizative [2+2] Cycloaddition Using Allenamides

Abstract Highly regio- and stereoselective homodimerizative [2+2] cycloaddition of allenamides under nickel catalysis was developed. Xantphos is an essential ligand to give “tail to tail” products and DFT studies revealed that oxidative addition between a nickel(0) complex and two distal C=C bonds of the allenamides would be a key process. Sequential formation of the metallacycle intermediate would proceed in both a regio- and stereoselective manner to give the corresponding cyclobutane as a single isomer.