Regio- and Redox Divergent Hydrated Ring Expansion of Butafulvenes

By providing highly functionalized building blocks in an efficient approach, catalytic hydration of alkenes plays a significant role in fundamental chemical transformations and pharmaceutical synthesis. However, hydration reactions have predominantly involved addition reactions of water and alkenes double bond. Herein, we developed a regio- and redox divergent hydrated ring expansion protocol of butafulvenes. With the aid of Pd^II or acid catalysis, various highly functionalized and unsaturated cyclopentanone derivatives could be obtained in high regioselectivities under oxidative or redox neutral conditions. Isotope labeling experiments suggest that the carbonylic oxygen atom of target product is derived from water. In addition, the unsaturated cyclopentanone intermediate could undergo divergent transformations and serve as a key molecule to create skeletal editing compounds of butafulvenes via one-pot protocol, which highlights the potential applications of this strategy.