Catalytic Oxidative α‐Functionalization of Carbonyls

Oxidative decarboxylative ammonium hypoiodite-catalysed dihydrobenzofuran synthesis

“…Attempts to render the whole process enantioselective by utilizing chiral ammonium iodide catalysts were unfortunately less satisfactory, as no noteworthy selectivities could be achieved by screening a variety of different catalysts under the established racemic conditions as well as using other solvents (er <55 : 45, Scheme 2B). In addition, we also tried to utilize (chiral) aryliodides as catalysts under oxidative conditions, 1,3,4 but no product formation could be observed at all, thus substantiating the need for the quaternary ammonium hypoiodite catalyst system herein.…”

“…1–3 The increasing research focus on this unique organocatalysis principle has led to the introduction of several valuable racemic as well as enantioselective transformations that are otherwise not easily possible with classical strategies. 2–10 Depending on the reaction conditions, oxidation of the iodide counter anion to different catalytically active higher oxidation state species (I 3 , IO n − ) can be achieved, amongst which ammonium hypoiodite derivatives R 4 N + IO − have been the most commonly postulated (and detected) catalytically relevant ones (simple oxidants like H 2 O 2 , oxone, or organic hydroperoxides can be used therefore) (Scheme 1A). These in situ formed species then allow for the oxidative Umpolung of the inherent reactivity of suited substrates ( e.g.…”

New Isoxazole‐Substituted Aryl Iodides: Metal‐Free Synthesis, Characterization and Catalytic Activity

“…[2,5,17] Certain alternative approaches for the oxidation of sulfides to sulfoxides include electrochemical methods, [18] photocatalytic oxidation using oxygen [19] etc. Besides oxidation reactions, various other valuable reactions such as alkene difunctionalization, [20][21] spiro cyclization of esters and amides [22][23] and oxytosylation and acetylation of ketones [24] have also been studied by the use of iodoarenes as catalysts. Recently, Nachtsheim group developed N-heterocyclic iodoarenes (NHIAs) as efficient organocatalysts in various oxidative transformations.…”

Synthesis of α-heterofunctionalized carbonyl compounds via Brønsted acid-catalyzed oxygenative coupling of ynamides

“…The α-heterofunctionalization of carbonyl compounds represents a highly valuable method for the synthesis of a variety of biologically active compounds and medicinally relevant heterocycles. 1 For this, activated carbonyl compounds or silyl enol ethers can undergo functionalization with electrophilic heteroatom sources, including peroxy compounds, dioxiranes, oxaziridines, and hydroxylamines (Scheme 1A). 2 Nevertheless, many of these reagents lack functional group compatibility.…”