nBu₄NI‐Catalyzed α‐Benzoxylation of Ketones with Terminal Aryl Alkenes

Abstract

A metal‐free protocol for the α‐benzoxylation of ketones has been developed by using terminal aryl alkenes as an arylcarboxy surrogate. Moderate to good yields were attained for a variety of propiophenones and acetophenones by using tetra‐n‐butylammonium iodide (TBAI) as the catalyst and tert‐butyl hydroperoxide (TBHP) as the oxidant under ambient reaction conditions.

Difunctionalization of alkenes with iodine and tert-butyl hydroperoxide (TBHP) at room temperature for the synthesis of 1-(tert-butylperoxy)-2-iodoethanes

“…In the presence of TBHP, a fast reaction between tert -butoxyl radicals and TBHP take place, leading to the formation of tert -butylperoxyl radicals and tertiary butanol [ 41 – 42 ]. Subsequently, the radical 3 can be further oxidized into cation 4 with I 2 [ 24 , 43 – 44 ]. The iodide ion is then reoxidized with TBHP to regenerate I 2 and tert -butoxyl radicals [ 24 , 45 ].…”

“…Subsequently, the radical 3 can be further oxidized into cation 4 with I 2 [ 24 , 43 – 44 ]. The iodide ion is then reoxidized with TBHP to regenerate I 2 and tert -butoxyl radicals [ 24 , 45 ]. Finally, cation 4 can be attacked by TBHP to give the final product 2a .…”

“…Traditional studies have mainly focused on transition-metal-catalyzed direct vicinal difunctionalization of alkenes by installing two substituents across the C=C double bond to form two new bonds or two new functional groups [ 7 – 9 ], such as dioxygenation [ 10 – 11 ], dihydroxylation [ 10 , 12 ], bisperoxidation [ 13 ], oxyamidation [ 14 ], aminohydroxylation [ 15 ], oxyphosphorylation [ 16 ], deamination [ 17 ] and carbonylation–peroxidation [ 18 ]. Several very recent reports have pertained to metal-free catalysts for difunctionalization of alkenes such as UV light [ 19 – 20 ], hypervalent iodine reagents [ 21 – 22 ], acids [ 23 ], organoammonium iodides [ 24 ] and iodine [ 25 ]. These catalysts are often employed in combination with a peroxide and generally produce an organoperoxide.…”

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

“…An I − /I 2 redox cycle promotes tert -butoxyl and tert -butylperoxyl radical formation from TBHP [26–28]. In the presence of TBHP and I 2 , α-iodoaryl ketones 5 and 6 are oxidized to a 1,2-diketone intermediate 7 and an α-carbonyl radical 9 , which can be further transformed to tert -butyl perester 8 and cation 11 [22]. The I − anion can be reoxidized by tert -butyl perester 8 to regenerate I 2 , a tert -butoxyl radical, and an aromatic acid anion under alkaline conditions.…”

C(sp3)–H Bond Functionalization of Alcohols, Ketones, Nitriles, Ethers and Amides using tert-Butyl Hydroperoxide as a Radical Initiator

“…Pan's group 26 reported the -benzoxylation of ketones using terminal aryl olefins as arylcarboxy surrogates and tetra-n-butylammonium iodide (TBAI) as the catalyst (Scheme 5). In this transformation, a variety of ketones were obtained under metal-free conditions, thus providing a mild and convenient approach for the -benzoxylation of ketones.…”