Rhodium(I)-catalyzed intramolecular carbonylative [2+2+1] cycloaddition of bis(allene)s: bicyclo[6.3.0]undecadienones and bicyclo[5.3.0]decadienones.

No templates needed: The title reaction makes it easy to construct the bicyclo[6.3.0]undecadienone framework in high yields (see scheme). A template effect is not required to achieve this ring-closing reaction efficiently. The present method can be applied to the construction of bicyclo[5.3.0] and bicyclo[4.3.0] ring systems. Ts = p-toluenesulfonyl.