Current Advances in Meerwein-type Radical Alkene Functionalizations

Abstract

Alkene functionalizations via Meerwein arylations are becoming increasingly attractive, especially since a variety of mild and sustainable methods for aryl radical generation are available today. This entails a broad spectrum of substrates and radical scavengers, as well as convenient synthetic routes to relevant precursors for further transformations. The present review focuses on recent advances in Meerwein-type alkene functionalizations and gives insights into the key mechanistic details of the respective reactions.1 Introduction2 Hydroarylation and Carboarylation3 Carboamination, Carbooxygenation, and Carbothiolation4 Carbohalogenation5 Conclusion and Outlook

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

“…Changing the sacrificial anode or cathode did not improve the reaction efficiency (Table 1, entries 4-7). The effects of a series of redox mediators on the reaction outcomes were examined, and none gave a better reaction outcome than 1,3-DCB (Table 1, entries [8][9][10][11][12]. Control experiments revealed that both visible-light irradiation and the presence of 1,3-DCB were essential for achieving the hydroarylation in high efficiency (Table 1, entries [13][14][15][16].…”

“…To achieve this transformation with high efficiency and predictable regioselectivity, numerous efforts have been made to develop transition-metal-catalyzed reactions based on a C-H activation strategy [1][2][3][4] or the reductive coupling of aryl halides with a hydride donor [5][6][7][8]. On the other hand, aryl radical-involved hydroarylation would be a promising alternative for the synthesis of alkylarenes with high anti-Markovnikov selectivity [9,10]. Aryl halides have received in-creased attention as ideal radical precursors because of their beneficial features, such as higher chemical stability and wide commercial availability, compared with other precursors, e.g., diazonium salts [11].…”

Three‐Component Reactions of Alkenes with C−C Bond Formation: Recent Developments

“…Diazoium salts (RN 2 X) are useful reagents due to their wide applications in radical chemistry, [4b] and stable crystalline salts such as ArN 2 BF 4 are attractive and mostly employed in carbon chain growth. The Heinrich group [4c] recently reviewed alkene difunctionalizations by diazoium salts. The intrinsic −SCF 3 group has strong electron‐withdrawing power and high lipophilicity that drastically alter the chemical, physical, and biological properties of molecules [4d,e] …”

Radical N2-Retention Cyclizations of Aryl Diazoniums: Access to 7/8/9-Membered Heterocycles

“…Aryl diazoniums are widely available synthetic building blocks as a result of the ubiquitous availability of parent aryl amines. Since their discovery in 1858, they have been recognized as one of the most versatile and important reagents in various organic transformations, including Sandmeyer reactions, Meerwein arylations, and Heck–Matsuda reactions . Generally, the reactions with aryl diazonium salts involve release of N 2 gas, making the reactions with diazonium salts atom-inefficient and potentially explosive .…”