Sulfur-Mediated Reactions through Sulfonium Salts and Ylides

Abstract

In this short review, some new reaction methods developed in our group that utilized sulfur mediated reactions through sulfonium salts and ylides are discussed, highlighting the interplay of rational design and serendipity. Our initial goal was to convert aliphatic C-H bond to C-C bond site-selectively without the use of transition metal catalysts. While proof-of-concept has been achieved, this target was by far not ideally realized. The unexpected discovery of an anti-Markovnikov rearrangement and subsequent studies on difunctionalization of alkynes were much more straightforward, and eventually led to the new possibility of asymmetric N-H insertion of sulfonium ylides through Brønsted acid catalysis.

Synthetic application of chalcogenonium salts: beyond sulfonium

“…Accordingly, the design, synthesis and application of these salts have been further explored. Alongside their known application as electrophilic 6 or ylide sources, 7 the synthetic use of sulfonium salts can be successfully extended to cross-coupling reactions 8 and the generation of carbon-centered radical species. 9…”

Asymmetric transformations from sulfoxonium ylides

“…First, it creates a Lewis base coordinate site, which can interfere in a catalytic cycle. [58][59][60] Second, the more positive sulfur atom leads to a better stabilization of the adjacent negative charge by electrostatic effect, making this compound less reactive and less Cnucleophilic when compared to the corresponding sulfonium ylide. After reading this paragraph the reader will realize how important is the development of new methods to synthesize sulfoxonium ylides and how room still exists for research in this area.…”

Rhodium-Catalyzed 1,4-Aryl Rearrangement of Sulfur Ylide for the Synthesis of 2-Pyridyl Thioethers

“…The TM-catalyzed rearrangement of sulfur ylides through carbene transfer is one of the most versatile bond-reorganization processes in organic chemistry and offers a platform for the formation of C–C and C–S bonds . Today, a variety of sulfur ylide rearrangement reactions have been developed, among which the [2,3]-rearrangements of ally/propargyl sulfides , and the [1,2]-rearrangements of benzylic/cyclic sulfides are probably the most studied systems (Scheme a).…”