Iron‐Mediated Cyanoalkylsulfonylation/Arylation of Active Alkenes with Cycloketone Oxime Derivatives via Sulfur Dioxide Insertion

Abstract

Iron‐mediated radical cyanoalkylsulfonylation/arylation of active olefins with cycloketone oxime derivatives via cleavage of C−C single bond and insertion of SO2 is developed for the preparation of cyanoalkylsulfonylated oxindoles. This difunctionalization of carbon−carbon double bond via a radical pathway involves cyclobutanone oxime ester fragmentation, sulfonyl radical generation and radical addition/5‐exo cyclization. The methodology displays good functional group tolerance and does not require any external bases or oxidants.magnified image

Recent advances in ring-opening of cyclobutanone oximes for capturing SO2, CO or O2via a radical process

“…The mechanism is outlined, and indicates that iminyl radical 4 was produced from cyclobutanone oximes in the presence of [Ru(bpy Construction of cyanoalkylsulfonylated oxindoles was accomplished through an iron-mediated reaction of active alkenes, potassium metabisulfite and cyclobutanone oximes with good functional group tolerance and without the addition of any external base, oxidant and ligand (Scheme 14). 57 This cascade radical cyanoalkylsulfonylation/arylation with insertion of sulfur dioxide was conducted by Liu and co-workers. In this transformation, potassium metabisulfites can afford sulfur dioxide.…”

The Renaissance of Alkali Metabisulfites as SO2 Surrogates

“…The method does not require any additional base or oxidant, which is one of the main advantages of the protocol (Scheme 16). 41 Scheme 16. Synthesis of 3-cyanoalkyl sulfonylated oxindoles.…”

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

“…Recently, Liu and co‐workers reported an iron‐catalyzed coupling reaction of acrylamides 103 , cycloketone oxime esters and K 2 S 2 O 5 for the synthesis of cyanoalkysulfonylated oxindoles 104 , which might proceed through ring cleavage, SO 2 insertion and intramolecular cyclization (Scheme 36). [48] Acrylamides with various substitutes on the aryl ring and nitrogen atom were well tolerated, affording cyanoalkysulfonylated oxindoles in moderate to good yields. However, acrylamides bearing an N−H group, N−Ac group or an ortho‐substitute failed to give the desired products.…”