Recent Developments in Radical Cross‐Coupling of Redox‐Active Cycloketone Oximes

Abstract

Recent years have witnessed a renaissance of radical cross‐coupling of cycloketone oximes which served as active cyanoalkyl radical via ring fragmentation in various transformations. It provided an efficient and practical strategy to introduce cyanoalkyl groups into organic compounds without using toxic cyanide sources. In this review, a comprehensive overview of recent advances in the field of redox‐active cycloketone oximes‐based cross‐couplings were covered. This review was categorized into two broad parts: non‐photocatalyzed and photocatalyzed cross‐couplings according to the reaction conditions. Moreover, the two broad parts were further divided into several sub‐sections depending on the nature of the bond formation. Some representative examples along with reaction mechanisms were also discussed.

Construction of sulfonated spiro[5,5]trienones from sulfur dioxide via iron-catalyzed dearomative spirocyclization of biaryls

“…We reasoned that initially, cycloketone oxime ester 2a would undergo a single electron transfer with Fe( ii ) to yield iminyl radical A and Fe( iii ). 13 Subsequently, cyanoalkyl radical B would be formed through the selective β-C–C bond cleavage of iminyl radical A , which rapidly reacted with sulfur dioxide to generate cyanoalkylsulfonyl radical C . The addition of cyanoalkylsulfonyl radical C to biaryl ynone 1a would give vinyl radical D .…”

Switchable radical carbonylation by polarity-regulation

“…Oxime esters that could be easily prepared from commercial ketones and carboxylic acids have recently proved to be a class of versatile cyanoalkyl radical precursors for many radical cross-coupling reactions under photoreduction conditions, as shown by us 38 and other groups. 39 To explore the application of polarity-regulation strategy in switchable radical carbonylation reactions, we chose a three-component carbonylative coupling among oxime ester 1a, aniline 2a, and CO (80 atm) as a model reaction (Fig. 2A).…”

Visible-Light-Promoted Selenocyanation of Cyclobutanone Oxime Esters Using Potassium Selenocyanate

“…Recently, cyclobutanone oxime esters have emerged as important intermediates in organic synthesis by converting to various functionalized alkyl nitriles via iminyl radicals . This type of transformation involves the formation of new carbon–carbon and carbon–X bonds and is realized by transition-metal catalysis, acid catalysis, microwave irradiation, photocatalysis, and Lewis base activation .…”