Oxidation under phase-transfer condition

Permanganates of zinc, sodium and benzyltriediylammonium have also been shown to be effective and selective oxidants to obtain sulfones from sulfides. The method of sulfoxide oxidation under phase-transfer conditions has also been developed using KMn04 and Cu(Mn04)2. ... 

Over-oxidation occurs if the solution is permitted to become basic. For example, 3-phenylpropene gives approximately equal amounts of phenylacetic acid and benzoic acid when oxidized under phase transfer conditions using a two-phase benzene/water solvent system. However, when acetic acid is added, the yield of phenylacetic acid increases to 80%. 

Oxidation of Organosulfur Compounds. Thiols are converted into disulfides using reagents such as Bis[trinitratocerium (TV)] Chromate. Chemoselective oxidation of sulfides by Ce reagents to sulfoxides is easily accomplished. Stoichiometric oxidation under phase transfer conditions and the dual oxidant protocols permit oxidation of a variety of sulfides. 

Kano T, Yamamoto A, Song S, Maruoka K (2011) Catalytic Asymmetric Syntheses of Isoxazoline-N-Oxides under Phase-Transfer Conditions. Chem Commun 47 4358... 

Starks has carried out an extensive study of olefin oxidation under phase transfer conditions. Unfortunately, with the exception of his work on permanganate ion which has been discussed, the results of these studies have appeared only in the patent literature [14, 15]. The oxidants used were 30% hydrogen peroxide or para-... 

Table 11.6. Catalytic oxidations under phase transfer conditions (14, 15] ...

Carbanions have been oxidized under phase transfer conditions in the presence of both crown ethers and cryptates. The substrate which has been most studied is fluorene which undergoes phase transfer catalyzed air oxidation to yield fluorenone in high yield according to equation 11.11 [10, 18]. Crown complexed f-butoxide in... 

The alkynyl iodide 150 undergoes the oxidative addition to form an alky-nylpalladium iodide, and subsequent insertion of an alkene gives the conjugated enyne 151 under phase-transfer conditions[120]. 

Excellent yields of the former product are also obtained with quinoline N-oxide. Improved yields of Reissert compounds are found under phase-transfer conditions (29). The regiochemistry of the method changes dramatically with /V-alkyl quin olinium salts, eg, /V-methy1quino1inium iodide [3947-76-0] (12), which form 4-cyanoquinoline [23395-72-4] (13) (30), through the intermediary in this example of A[-methyl-4-cyano-l,4-dihydroquinoline... 

The dimethyl ethers of hydroquiaones and 1,4-naphthalenediols can be oxidized with silver(II) oxide or ceric ammonium nitrate. Aqueous sodium hypochlorite under phase-transfer conditions has also produced efficient conversion of catechols and hydroquiaones to 1,2- and 1,4-benzoquiaones (116), eg, 4-/-butyl-l,2-ben2oquinone [1129-21-1] ia 92% yield. 

Oxidation ofpentafluoroaniline by sodium hypochlorite under phase-transfer conditions leads to perfluoroazobenzene as the main product [86] (equation 78)... 

Generation of the anion of 5,7-diphenyl-5//-dibenz[c,e]azepine (6) under phase-transfer conditions in the presence of air results in oxidation and formation of the dibenz[c,c]azepinol 7 whose structure was confirmed by X-ray crystallography.85... 

Epoxidation systems based on molybdenum and tungsten catalysts have been extensively studied for more than 40 years. The typical catalysts - MoVI-oxo or WVI-oxo species - do, however, behave rather differently, depending on whether anionic or neutral complexes are employed. Whereas the anionic catalysts, especially the use of tungstates under phase-transfer conditions, are able to activate aqueous hydrogen peroxide efficiently for the formation of epoxides, neutral molybdenum or tungsten complexes do react with hydrogen peroxide, but better selectivities are often achieved with organic hydroperoxides (e.g., TBHP) as terminal oxidants [44, 45],... 

Unsymmetrical as well as symmetrical anhydrides are often prepared by the treatment of an acyl halide with a carboxylic acid salt. The compound C0CI2 has been used as a catalyst. If a metallic salt is used, Na , K , or Ag are the most common cations, but more often pyridine or another tertiary amine is added to the free acid and the salt thus formed is treated with the acyl halide. Mixed formic anhydrides are prepared from sodium formate and an aryl halide, by use of a solid-phase copolymer of pyridine-l-oxide. Symmetrical anhydrides can be prepared by reaction of the acyl halide with aqueous NaOH or NaHCOa under phase-transfer conditions, or with sodium bicarbonate with ultrasound. 

Primary and secondary aliphatic nitro compounds have been oxidized to aldehydes and ketones, respectively (RR CHN02 RR C=0) with sodium chlorite under phase-transfer conditions, TPAP, Oxone , as well as with other reagents. 

Epoxidation with sodium hypochlorite.1 Ni(salen), is an effective catalyst for oxidation of some alkenes with NaOCl under phase-transfer conditions. Styrenes... 

This methodology provides a general synthesis of L-amino acids in 92-96% ee and in chemical yields of about 40-60%. Thus reaction of 3 (X = Br) with NaN3 under phase-transfer conditions provides 6, which is homologated to the 1-chloro-2-azidoboronate 7. This product is oxidized by sodium chlorite directly to an azido carboxylic acid (8). Hydrogenation of 8 provides L-amino acids (9). 

Wacker oxidation of styrene has also been performed in [bmim][BF4] and [bmim][PF6], at 60 °C with H2O2 and PdCF as a catalyst [19]. This system gave yields of acetophenone as high as 92 % after 3 h. Hydrogen peroxide may also be used under phase transfer conditions for alkene bond cleavage, to produce adipic acid (an intermediate in the synthesis of nylon-6) from cyclohexene (Scheme 9.9). 

As indicated above, the traditional base-catalysed hydrolysis of 0,5-dialkyl thio-carbonates for the synthesis of thiols is generally unsatisfactory, as oxidation leads to the formation of disulphides. Under phase-transfer conditions, the procedure produces thioethers to the virtual exclusion of the thiols, as a result of the slow release of the thiolate anions in the presence of the electrophilic ester. However, a simple modification of the reaction conditions provides an efficient one-pot reaction [50] from haloalkanes (Table 4.15) via the intermediate formation of the thermally labile (9-/ert-butyl-5-alkyl dithiocarbonates (Scheme 4.8). 

Toluene has been converted into benzyl chloride (67%) by hypochlorite under phase-transfer conditions, but the procedure does not appear to have been exploited generally, possibly because of competing arene epoxidation [16]. Oxidation of 2,5-di-f-butylfuran yields 2,2,7,7-tetramethyloct-4-en-3,6-dione (83%) [17]. 

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