Recent Advances on Annulation Reactions with Allyl and Propargyl Sulfonium Salts

Allyl and propargyl sulfonium salts are readily available reagents and have recently emerged as versatile building blocks in the assembly of cyclic skeletons. As an alternative to the classical sulfonium salts, allyl and propargyl sulfonium salts can convert to the corresponding vinyl sulfur ylide or allenic sulfonium salt intermediates that contain diverse nucleophilic or electrophilic reactive positions, thereby enabling a great variety of annulation reactions. In this review, we provide a comprehensive overview of the recent developments on this growing field by summarizing the annulation reactions involving allyl and propargyl sulfonium salts.

Cooperative copper-squaramide catalysis for the enantioselective N–H insertion reaction with sulfoxonium ylides

The first examples of a highly efficient and enantioselective carbene-mediated insertion reaction, from a sulfur ylide, are described.

Conversion of anilines to chiral benzylic amines via formal one-carbon insertion into aromatic C–N bonds

Insertion of atoms into aromatic carbon-nitrogen bonds is an appealing method for the synthesis of nitrogen-containing molecules and it has the advantage of the availability and abundance of anilines. However, the direct cleavage of aromatic carbon-nitrogen bonds is challenging due to the particularly inert and stable nature of these bonds. Here we report a formal, enantioselective one-carbon insertion into an aromatic carbon-nitrogen bond via an aromaticity dissembly-reconstruction process to directly convert anilines to chiral α-branched benzylic amines. The process involves oxidative dearomatization of para-substituted anilines, chiral sulfur ylide-mediated asymmetric aziridination, and subsequent rearrangement. Chiral sulfur ylides serve as one-carbon insertion units.

Efficiently diastereoselective synthesis of functionalized hydro-carbazoles by base-mediated tandem annulation of 1-(2-amino-aryl)prop-2-en-1-ones and sulfur ylide

The base-promoted [3 + 3]/[1 + 4] tandem reaction of tosyl-protected o-amino α,β-unsaturated ketones and crotonate-derived sulfur ylide is developed for efficiently diastereoselective synthesis of functionalized hydrocarbazoles.