α‐Arylation of Carbonyl Compounds through Oxidative C−C Bond Activation

Abstract

A synthetically useful approach for the direct α‐arylation of carbonyl compounds through a novel oxidative C−C bond activation is reported. This mechanistically unusual process relies on a 1,2‐aryl shift and results in all‐carbon quaternary centers. The transformation displays broad functional‐group tolerance and can in principle also be applied as an asymmetric variant.

An α‐Cyclopropanation of Carbonyl Derivatives by Oxidative Umpolung

“…Instead, skeletal rearrangements are observed leading to stabilized carbocationic intermediates. Net 1,2‐phenyl migrations for instance which proceed via a phenonium intermediate are frequently witnessed (Scheme b) . This illustrates that α‐umpolung chemistry of carbonyl compounds can be leveraged to a new avenue for carbocationic rearrangements which no longer require halide/leaving group abstractions or protonation of carbon–carbon multiple bonds .…”

“…Net 1,2-phenyl migrations for instance which proceed via a phenonium intermediate [45,46] are frequently witnessed (Scheme 1 b). [47][48][49] This illustrates that aumpolung chemistry of carbonyl compounds can be leveraged to a new avenue for carbocationic rearrangements which no longer require halide/leaving group abstractions [50,51] or protonation of carbon-carbon multiple bonds. [52][53][54] Building on these developments, we herein report a new protocol for cyclopropanation by exploiting the propensity of certain enolonium species to engage in carbocationic rearrangements.…”

Recent discoveries on the structure of iodine(iii) reagents and their use in cross-nucleophile coupling

“… 148 Similarly, the oxidation of β-aryl active methylene compounds may lead to a 1,2-aryl migration with subsequent capture of the transient phenonium ion by the secondary nucleophile ( Scheme 10d ). 149 Another interesting example is the use of iodine( iii ) on cyclic active methine substrates. In these cases, the enolonium species 96 ( cf.…”

Synthesis and Characterization of 1,10-Phenanthroline-mono-N-oxides

“…N-oxides of heterocycles are of great importance due to their widespread applicability, including, but not limited to, manufacturing chirality chemosensors [1], oxidizing agents in annulation reactions [2], intramolecular oxidants in Baeyer-Villiger reaction of ketones [3], directing group and source of oxygen atom in sulfonylation reactions [4], phase-transfer catalysts in enantioselective transformations [5], starting materials in C-C bond forming processes [6][7][8][9], or in the synthesis of 2-aminopyridines [10] and N-azine sulfoximines [11]. Recently published papers have discussed the cycloaddition reactions of N-oxides [12], their photochemistry [13,14] and their applications in organocatalysis [15][16][17].…”