An efficient catalytic (2 + 2)-cycloaddition reaction leading to the formation of cyclobutane rings has been devised. The process transforms silyl enol ethers and α,β-unsaturated esters into polysubstituted cyclobutanes with a high degree of trans-stereoselectivity. Both the rate and stereoselectivity of the process can be controlled by the choice of the ester group and silyl substituents. The results
Treatment of keto-esters 1-5 with Bu(2)BOTf and (TMS)(2)NH caused a tandem Michael-aldol reaction to give polycyclic cyclobutanes 6-10 with high stereoselection. It was proved that the reaction was accelerated by the addition of Bu(4)NI.