The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

Abstract

Summary N-acyliminium ions are useful reactive synthetic intermediates in a variety of important carbon–carbon bond forming and cyclisation strategies in organic chemistry. The advent of an electrochemical anodic oxidation of unfunctionalised amides, more commonly known as the Shono oxidation, has provided a complementary route to the C–H activation of low reactivity intermediates. In this article, containing over 100 references, we highlight the development of the Shono-type oxidations from the original direct electrolysis methods, to the use of electroauxiliaries before arriving at indirect electrolysis methodologies. We also highlight new technologies and techniques applied to this area of electrosynthesis. We conclude with the use of this electrosynthetic approach to challenging syntheses of natural products and other complex structures for biological evaluation discussing recent technological developments in electroorganic techniques and future directions.

Scalable, Electrochemical Oxidation of Unactivated C–H Bonds

“…In 11 , not only was the phthalimide tolerated under the reaction conditions, but the α-C–H bond was also preserved—no noticeable α-oxidation (Shono-type) took place. 16 12 was obtained with complete retention of stereochemical integrity, despite the presence of two epimerizable centers. Selective distal methylene oxidation was observed in 13 wherein the pyridine motif and the benzylic methylene group both remained intact.…”

Anodic Oxidation as an Enabling Tool for the Synthesis of Natural Products

“…Elementary electrochemistry involving cathodic and anodic reactions, its application in organic synthesis and special techniques such as continuous-flow electrochemistry, [32][33][34] as well as redoxmediated electrosynthesis, [35][36][37] have been the subject of several review articles. [38][39][40][41][42][43][44][45][46][47][48][49][50] In the present review, selected examples of applications of electroorganic synthesis in the construction of complex natural product frameworks are highlighted with a focus on L. Geske et al…”

Rapid Access to Polyfunctionalized 3,4‐Dihydroquinazolinones through a Sequential N‐Acyliminium Ion Mannich Reaction Cascade

“…The main goal of the present study is to investigate the scope of unactivated ketones in the reaction with N ‐acyliminium49–54 ion I for the synthesis of highly functionalized 3,4‐dihydroquinazolinone scaffold libraries and improve the developed protocol. Therefore, we have proposed a Mannich‐based strategy for the preparation of polyfunctionalized 3,4‐dihydroquinazolinones that generates four points of diversity by using unactivated methyl alkyl/aryl ketones (p K a > 20) with cyclic N ‐acyliminium ions I , which are generated in situ from o ‐formyl carbamates and amines (Scheme ).…”