Recent advances in Pummerer reactions

The Pummerer and Pummerer-type reactions of sulfoxides generate sulfonium ion intermediates, to which either internal or external nucleophilic species add to form carbon-carbon and carbon-heteroatom bonds at the alpha-position of the sulfur functional groups. Lately, various kinds of new reactions initiated by the Pummerer and Pummerer-type reactions have been developed. These reactions have received considerable attention as synthetically useful tools and have been applied to total syntheses of biologically important natural products and highly functionalized unnatural compounds. This review focuses on recent remarkable progress in these chemistries, published in 2001 and later. The main topics involve (i) optically active sulfoxides as both chiral auxiliaries and carbonyl equivalents, (ii) the domino bond-forming reactions, (iii) the asymmetric Pummerer reactions, (iv) the aromatic Pummerer-type reactions, (v) the interrupted Pummerer reactions, and (vi) the fluorination reactions.