Synthesis of monocyclic nine-membered compounds by the [4+3+2] cycloaddition-bond cleavage strategy

Monocyclic nine-membered compounds were synthesized by the cleavage of the six-membered ring of the bicyclic compounds. Thus, the bicyclic compounds which consist of six- and nine-membered rings were synthesized by the Ni-catalyzed [4+3+2] cycloaddition, and the cleavage of the N–O bond, which was incorporated in the six-membered ring, proceeded in the presence of Mo(CO)6 to yield the monocyclic compound. On the other hand, the cleavage of the C–O bond proceeded efficiently in the presence of SmI2.