RhI -Catalyzed Carbonylative [3+1] Construction of Cyclobutenones via C-C σ-Bond Activation of Cyclopropenes.

With a catalytic amount of Rh(cod)2 BF4 and dppm, cyclopropenes undergo a direct carbonylative [3+1] cycloaddition reaction under an atmosphere of CO to produce the cyclobutenones in excellent yields, in which the regio- and diastereoselectivities can be controlled in certain cases with the help of chelating groups. Cyclobutenone with a chiral 4-position was prepared by diastereoselective induction. Rhodacyclopentenone has been determined as the key intermediate, as it was synthesized and applied to the reductive elimination step.