Water-controlled and phosphine-mediated selective synthesis of saturated 1,4-diketones and tetrasubstituted furans has been developed directly from 1,4-enediones. Saturated 1,4-diketones were selectively obtained in acetone with water as an additive, whereas tetrasubstituted furans were selectively obtained in anhydrous 1,2-dichloroethane. A large variety of functional groups are tolerated under these reaction conditions, including electron-rich, electron-poor, halogen, and heteroaryl substituents. This method also has significant advantages in easily available substrates, mild reaction condit...