Photocatalytic Synthesis of β‐Sulfonated Cyclopentanones via Sulfonylation and Semipinacol‐type Rearrangement Cascades of Vinyl Cyclobutanols

Organic Sulfinic Acids and Salts in Visible Light-Induced Reactions

Sulfinic acids and their salts are a useful source of sulfur-containing structures. Photocatalysis of these compounds with visible light enables to achieve various transformations under mild conditions. This review summarizes visible-light-induced reactions of sulfinic acids and their salts. It is organized by reaction type and brief discussions on plausible reaction mechanisms for typical transformations are presented.

1 Introduction

2 Sulfonylation Reactions

2.1 Sulfonylation of Alkenes

2.2 Sulfonylation of Alkynes

2.3 Sulfonylation of Arenes

2.4 sp3 C–H Functionalization

3 Desulfonylation Reactions

4 Sulfenylation Reactions

4.1 Sulfenylation of Heteroarenes

4.2 Sulfenylation of Carbonyl Chlorides

5 Conclusions

Recent development and applications of semipinacol rearrangement reactions

As has been well-recognized, semipinacol rearrangement functions as an exceptionally useful methodology in the synthesis of β-functionalized ketones, creation of quaternary carbon centers, and construction of challenging carbocycles. Due to their versatile utilities in organic synthesis, development of novel rearrangement reactions has been a vibrant topic that continues to shape the research field. Recent breakthroughs in novel electrophiles, tandem processes, and enantioselective catalytic transformations further enrich the toolbox of this chemistry and spur the strategic applications of this methodology in natural product synthesis. These achievements will be discussed in this minireview.

Small rings in the bigger picture: ring expansion of three- and four-membered rings to access larger all-carbon cyclic systems

The release of the inherent ring strain of cyclobutane and cyclopropane derivatives allows a rapid build-up of molecular complexity. This review highlights the state-of-the-art of the ring expansions of three- and four-membered cycles and is organised by types of reactions with emphasis on the reaction mechanisms. Selected examples are discussed to illustrate the synthetic potential of this elegant synthetic tool.