Gold(l)-catalyzed Enantioselective Synthesis Of Benzopyrans Via Rearrangement Of Allylic Oxonium Intermediates

摘要

The gold-catalyzed 1,2-rearrangement of propargyl esters has provided the basis for the development of a wide range of transformations. These reactions are proposed to proceed through gold-stabilized cationic intermediates (A) that show reactivity analogous to electrophilic transition metal carbenoids. Despite the current interest in reactions involving these intermediates, very few examples of enantioselective transformations have been described. We have recently reported that chiral biarylphosphinegold(I) complexes catalyze the enantioselective cyclopropanation of alkenes with propargyl esters (eq 1). We hypothesized that related gold(I) complexes might exert enantioface control on the addition of nucleophiles to prochiral vinylcarbenoid intermediate A.