Carbonyl‐Oxygen‐Assisted KOMe‐Mediated Formal Hydration of 4‐Alkynones: Complete Regioselectivity in the One‐Pot Synthesis of 1,4‐Diketones under Mild Conditions

An effective carbonyl‐oxygen‐assisted transition‐metal‐free approach was developed for the one‐pot synthesis of 1,4‐diketones through the formal hydration of 4‐alkynones with complete regioselectivity under mild conditions. The reaction tolerates a wide range of functional groups, and the corresponding functionalized 1,4‐diketones were obtained in moderate to excellent yields (up to 94 %). Importantly, the complete regioselectivity was attributed to the fact that 2,3‐dihydrofuran intermediates were obtained as single products through the 5‐ exo ‐ dig cyclization of 4‐alkynones; this was supported by control and isotope‐labeling experiments.