Recent Advances in the Synthesis of β‐Functionalized Ketones by Radical‐Mediated 1,2‐Rearrangement of Allylic Alcohols

Abstract

β-Functionalized ketones are a highly important and valuable class of compounds that have gained increasing attention from organic chemists due to their intensive uses as versatile synthetic intermediates and building blocks in complex molecule assembly and natural product synthesis. Accordingly, there is continuing interest in the development of new approaches for the synthesis of β-functionalized ketones. In recent years, radical-mediated 1,2-rearrangement reactions of allylic alcohols, which proceed through cationic (semipinacol) rearrangements or radical (neophyl) rearrangements, have presented an attractive and powerful strategy to access various diversely β-functionalized ketones. Interestingly, this strategy allows for the direct installation of a variety of valuable functional groups at the β-position of cyclic and acyclic ketones by employing different radical precursors. However, a review focusing on the preparation of β-functionalized ketones by radical-mediated 1,2-rearrangement reactions of allylic alcohols has not been summarized to date. This Minireview highlights recent progress made in this highly active and interesting research area, and the corresponding mechanisms will also be discussed.

Visible light-mediated C P bond formation reactions

“…Recently, visible light-mediated radical migration reactions have been recognized as a powerful method to trigger CAC and CAH bond functionalization [47][48][49]. Along these lines, Zhang group [50] developed an elegant method for the synthesis of baryl-c-ketophosphine oxides by using visible light-promoted 1,2aryl migration as the key step (Scheme 6).…”

Recent development and applications of semipinacol rearrangement reactions

“…However, when the migrating group is an arene or heteroarene, a neophyl-type 1,2-radical migration followed by oxidation is usually suggested ( Table 1 , path b). Although a wide range of electrophiles capable of initiating the rearrangement have been well-documented, 3,5 interest in the discovery of novel types of electrophiles and radical initiators 4,28 continues. Among these breakthroughs, novel catalytic techniques, such as photocatalysis and electrocatalysis, have also enabled reactions under environmentally benign conditions, thus preventing the use of excess oxidants or toxic reagents.…”

“…2,3 Generally, despite the diverse reaction patterns semipinacol rearrangement may involve, a typical process oen entails the generation of a carbonyl group through a 1,2-C-C or C-H bond migration from an oxygen-containing carbon to a vicinal carbon center, which is archetypally an electrophilic carbon 3 though a C-radical center has also been suggested in recent emerging radical rearrangements (Scheme 1). 4 A noteworthy aspect of this class of 1,2migration reactions is that it provides a reliable and efficient approach to access synthetically useful b-functionalized ketones. In addition, the semipinacol rearrangement also serves as a potent and versatile method for the construction of quaternary carbon centers 5 that are challenging to create but pervasive in natural molecules and pharmaceuticals.…”

“…As the development of semipinacol rearrangement in the last two decades has gradually become mature, summarization of a certain aspect of the venerable reaction has been documented in several previous reviews. [2][3][4][5][14][15][16][17] Nonetheless, recent advances of semipinacol rearrangement in terms of novel electrophiles, radical processes, 4 tandem reactions, and catalytic Xiao-Ming Zhang studied chemistry at Lanzhou University where he received his B.S. in 2007.…”

“…As the development of semipinacol rearrangement in the last two decades has gradually become mature, summarization of a certain aspect of the venerable reaction has been documented in several previous reviews. 2–5,14–17 Nonetheless, recent advances of semipinacol rearrangement in terms of novel electrophiles, radical processes, 4 tandem reactions, and catalytic enantioselective transformations 16,17 have further enriched the repertoire of this chemistry. These breakthroughs are accompanied by the prevailing application of the rearrangement reactions as a key step/strategy in the assembly of complex natural products.…”