An indole synthesis via ring expansion of benzocyclobutenone oxime sulfonate was developed. Utility of the indole synthesis was demonstrated by the total synthesis of (+)-CC-1065. The middle and right segments were constructed by a sequential ring expansion of the symmetrical benzo-bis-cyclobutenone. The left segment was also constructed via ring expansion of the methyl-substituted benzocyclobutenone oxime sulfonates. After condensation of these three segments, the dienone cyclopropane structure was formed to complete the total synthesis.

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The article discusses DIBALH‐mediated reductive ring‐expansion reaction of cyclic ketoxime. In contrast to the Beckmann rearrangement, the two possible geometries of the oxime C–N double bond can give exclusively an aromatic secondary amine in the presented method.