Mechanistic insights into the gold(i)-catalyzed [3,3]-sigmatropic rearrangement of sulfoniums for the formation of chiral 1,4-dicarbonyls or formal α-arylation of carbonyl compounds†

Abstract

Starting with vinyl sulfoxides and propargyl silane, the Au(i)-catalyzed asymmetric [3,3]-sigmatropic rearrangement of sulfonium intermediates furnished, after a protodemetallation step and hydrolysis of a thionium ion, the corresponding 4-oxo-2-aryl-2-alkyl-pentanal derivatives. From the fine analysis of crude mixtures representative of this transformation, formal α-arylated products of acetone (1-arylpropan-2-one derivatives) and aryl sulfanes were also isolated and characterized, depending on the substrates and reaction conditions used. Therefore, a tentative mechanistic explanation of the formation of these unexpected products was highlighted and DFT calculations have also streamlined the reactivity of these cationic gold(i)-catalyzed transformations.