Iron–surfactant nanocomposite-catalyzed benzylic oxidation in water

Abstract

Benzylic oxidation the presence of iron-surfactant nanocomposite catalyst under aqueous conditions is described. The significant 5 reaction rate acceleration by the presence of anionic surfactants was demonstrated. Several benzylic substrates were efficiently transformed to ketones under mild conditions.Oxidation of methyl or methylene group to carbonyl compounds is one of the most important synthetic transformation in organic chemistry.1 Activated methylene group by neighboring carbonyl moiety can be easily oxidized with selenium dioxide to obtain keto-10 aldehydes and diketones. 2 Benzylic CH 2 group also have high reactivity toward oxidizing agents, and aryl ketones are synthesized with high efficiency. However, to achieve this transformation toxic heavy metal based oxidants such as CrO 3 , 3 Jones reagent, 4 PCC is necessary.5 Development and utilization of environmentally benign catalytic oxidation processes have high relevance in current organic synthesis. Iron based catalyst system for the oxidation of alkanes was introduced by Barton in the early 80's.6 Since its discovery, several developments and extensions of the Gif chemistry have been achieved in the last decades.7 Besides the advantageous application of non-15 toxic iron catalysts for the oxidation of methylene group, the utilization of aqueous tert-butyl hydroperoxide (TBHP) as oxidant in pyridine 8 or in water 9 makes the process even more environmentally friendly. Catalytic transformations under micellar conditions in water can be performed efficiently with the aid of surfactant molecules.10 The formed micelles in aqueous solutions ensures better solubility of non polar organic molecules, and microcompartmentalize reactants which results improved reaction rates due to increased local concentrations inside the micelles. 20Besides the significant influence of surfactant molecules on solubility of organic compounds in water, alkyl sulfates and iron salts are able to build up organized composites with controlled thickness of inorganic layers containing bridged iron ions 11 . The close proximity of iron ions bridged by oxide in non-heme type metalloenzyme models is responsible for oxygen activation and oxidation of alkanes. 12Based on the well defined structure of self assembled iron oxide/surfactant composites we aimed to utilize iron-oxide/sodium dodecylsulfate composite material to mimic the 25 enhanced oxidation ability of diiron complexes. Herein, we describe an efficient protocol for the iron catalyzed benzylic oxidation of organic compounds with iron-surfactant nanocomposites using t BuOOH as oxidant. In our study, we examined several reaction parameters and the effect of surfactants on the reaction rate. TBHP solution is frequently used as applicable oxidant for the iron catalyzed oxidation of benzylic CH 2 group. 8, 9, 13, 14 Therefore we chose aqueous solution of TBHP as oxidant for the preliminary studies. The aqueous reactions were carried out in 5w/w% 30 solution of sodium-dodecylsulfate (SDS) to build up ironoxide/surfactant composit...

Recent advances in catalysis in micellar media

“…Novák and coworkers proposed the use of t-butyl hydroperoxide as the terminal oxidant in the presence of simple Fe(III) species such as FeCl 3 or Fe 2 (SO 4 ) 3 as an environmentally friendly metal catalyst in the presence of the anionic surfactant SDS to promote efficient substrate dissolution and consequent reaction (Scheme 25). 82 With this protocol more than two dozens of substituted aromatic substrates bearing the benzyl moiety and which are sufficiently electron rich were smoothly converted into the corresponding carbonyl compounds with high rate acceleration.…”

Surfactant-Assisted Selective Oxidation of Aromatic Amines to Nitro Compounds by in Situ-Formed Performic Acid

“…25 Novák and co-workers have proposed the oxidation of benzyl alcohol, and the reaction rate was increased by using an anionic surfactant, sodium dodecyl sulfate, for the dissolution of the substrate. 26 The amphiphilic nature of the surfactants controls the selectivity of the product by altering the reaction rate and chemoselectivity. 23 Thus, we also used various surfactants like trimethyl(tetra-decyl ammonium bromide), CTAB, poly(vinyl pyrrolidone), and potassium bromide as additives in this reaction.…”

Palladium Catalyzed Direct Acylation of Iodo‐Acetanilides/Iodo‐Phenyl Acetates: Domino One‐Pot Synthesis of 2‐Quinolinones

“…To our delight, the efficacy of method was further proven by successful transformation of ortho ‐iodophenyl acetates 1i to corresponding ketones 4ia – 4if (Table ). Notably, the method was also amenable with para ‐iodophenyl acetates 1j (Table , 4ja – 4jf ) …”

“…Products 3aa , 3ae , 3af , 3ag , 3ai , 3aj , 3al , 3am , 3ap , 3ar , 3as , 3at , 3bb , 3da , 3ea , 3ga , 3ha , 4ia , 4ib , 4if , 4ik , 4ja , 4jb , and 4jf are reported in literature. [12a], [12b], [12c], [12d], [12e], [12f], …”