Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.0¹,⁵]dodecenone

The [RhCl(CO)dppp](2)-catalyzed intramolecular carbonylative [2 + 2 + 1] cycloaddition of allenenes was developed to prepare bicyclo[4.3.0]nonenones possessing a methyl group at the ring junction, which is difficult to achieve by the Pauson-Khand reaction of the corresponding enynes. This method also provided a new procedure for the construction of the tricyclo[6.4.0.0(1,5)]dodecenone framework in a satisfactory yield.