1,3-O-Transposition or Trisubstituted Z-Enol Ester? A Comparative Study of Reactions of Ynones

Ynones are useful substrates for transition-metal-mediated synthesis. The Au^I-catalyzed 1,3-O-transposition is an important reaction of ynones. Recently, an efficient Cu^I-catalyzed synthesis of trisubstituted Z-enol esters via interrupting the traditional 1,3-O-transposition reaction of ynones was reported by Zhu's group. Herein, density functional theory studies disclosed that the hydrogen bond formed by carboxylic acid plays an important role for the reactivity and selectivity in this novel reaction. A qualitative rule was also found to explain the substituent effect in the ynone substrate, and this is consistent with experiments. The Au^I-catalyst and Cu^I-catalyst were further compared to interpret the essential cause of why the Au^I-catalyst prefers the 1,3-O-transpostion reaction. These conclusions might be helpful for the rational design of reactions of ynones.