Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.0^1,5]dodecenone

• Fuyuhiko Inagaki,
• Naoya Itoh,
• Yujiro Hayashi,
• Yumi Matsui and
• Chisato Mukai

Beilstein J. Org. Chem. 2011, 7, 404–409, doi:10.3762/bjoc.7.52

• 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[6.4.0.01,5]dodecenone framework in a satisfactory yield. Keywords: allene; bicyclo[4.3.0] derivatives; carbonylative [2 + 2 + 1] cycloaddition; quaternary center construction; rhodium; Introduction The Co2(CO)8-mediated Pauson–Khand reaction (PKR) [1][2] is well recognized as a formal [2 + 2 + 1

• methyl group, and for the construction of the tricyclo[6.4.0.01,5]dodecenone skeleton. Results and Discussion In previous studies, we investigated the carbonylative [2 + 2 + 1] cycloaddition reaction of two allenenes 1 and 4 with either a SO2Ph or CO2Me substituent on the proximal double bond of the