One-pot oxidation

Recently, several one-pot oxidation-Wittig procedures that circumvent the need to isolate the intermediate aldehydes have been developed. Various oxidants, including Swern [52], Dess-Martin periodinane [53], IBX [54], Mn02 [55], and BaMnCU [56], can be used in the presence of stabilized ylides to generate a,(3-unsaturated esters. 

Novel heteroquaterphenoquinones were synthesized by a stepwise cross-coupling reaction or by a more convenient one-pot oxidative homocoupling reaction of the heterocycle-substituted phenols (Scheme 20, <96JOC4784 see also 95TL8055>). 

Innovative One-Pot Oxidation Method for the Synthesis of Bioproducts from Renewables... 

A conjugated homobimetallic palladium(II) complex (see Figure 40) was formed by one-pot oxidative complexation of 1,4-phenylenediamine with a palladium(II) complex bearing the tri-dentate ligand shown. In the absence of 1,4-phenylenediamine this palladium(II) complex undergoes controlled formation of a macrocyclic tetramer via removal of a labile solvent ligand, as shown in Figure 41.514... 

Figure 40 A conjugated homobimetallic palladium(II) complex, formed by one-pot oxidative complexation of 1,4-phenylenediamine with a palladium(II) complex bearing the tridentate ligand.

Dithiodimorpholine, 23 642 l,3-Dithiole-2-thiones, thiocrowned and oxothiocrowned, 23 707 Dithiols, one-pot oxidation polymerization of, 23 713... 

One-part solvent-releasing butyl sealant formulation, 22 43t One-part urethane sealants, 22 36-37 One-pass clarifier, 22 61 One-photon absorption, 77 455 One-pot oxidation polymerization, 23 713 One-stage separation plants, 75 840 One-step cameras/processors, 79 276-278 One-step Ziegler process, 77 715-718 One-way memory, of shape-memory alloys, 22 341, 345-346... 

In the same year an efficient one-pot oxidation and reduction sequence was also described for the cleavage of 1,2-diols to their corresponding primary alcohols [42]. This process was an excellent demonstration of two immobilized incompati-... 

Kroutil et al. have recently reported [18] an elegant one-pot oxidation/reduction sequence for the deracemization of a chiral secondary alcohol using a single biocatalyst. LyophiUzed cells of a Rhodococcus sp. CBS IVJ.Ti converted racemic 2-decanol into the (S)-enantiomer in 82% yield and 92% enantiomeric excess (e.e.). via a non-specific oxidation followed sequentially by an (S)-selective reduction (Scheme 6.5). Acetone was used as the hydrogen acceptor in the first step and isopropanol as the hydrogen donor in the second step. 

A number of 3-(alditol-l-yl)-5-methyl-7-oxo-l,2,4-triazolo[4,3-a]pyrim-idines l,2,4-triazolo[4,3-a]pyrimidines acyclo C-nucleosides (30) were synthesized (95PHA784) by oxidative cyclization of the corresponding aldehydo-sugar pyrimidin-2-ylhydrazones 27 with bromine in water. The alternative structure 29 was eliminated based on finding that acetylation of 30 afforded the same acetylated acyclo C-nucleosides 31 as those obtained by oxidative cyclization of the (A3-acetyl-poly-0-acetyl)hydrazones 28. Compounds 31 were also obtained by one-pot oxidative cyclization and acetylation of 27. In contrast to the oxidation and concurrent bromination of 19 to 25, it was possible to avoid nuclear bromination of 27 and 28 by performing the reaction in the absence of light (Scheme 13). 

Nevertheless, Celia et al. have proved that employing MCPBA as secondary oxidant in TEMPO-mediated oxidations may have a number of advantages when a one-pot oxidation of an alcohol with a concurrent alkene epoxidation or a Baeyer-Villiger oxidation is desired.6 The use of MCPBA as a secondary oxidant in TEMPO-mediated alcohol oxidations was recently reviewed.7... 

When an oxidation with Mn02 leads to an enone containing a properly positioned amine, an intramolecular conjugated addition of the amine to the enone can occur, resulting in a useful one-pot oxidation followed by heterocycle formation.63... 

Immobilized TEMPO has been used for the one-pot oxidation of alcohols to carboxylic acids as well.26 For this purpose TEMPO resin 1 was combined with two ion-exchange resins loaded with chlorite anions and hydrogen phosphate in the presence of catalytic amounts of potassium bromide and sodium hypochlorite in solution. The reaction required work-up for the removal of salts, but tolerated several protecting schemes and afforded pure products in good to excellent yields. The reaction is initiated by catalytic TEMPO oxidation of alcohols to aldehydes driven by dissolved hypochlorite followed by oxidation to the carboxylic acids effected by chlorite. 

Scheme 11. One-pot oxidation and Wittig reaction to a,/i-unsaturated esters...

Catalytic amounts of RuC13 with NaI04 as the co-oxidant provides one-pot oxidation of 39.10 19 The active agent Ru04 is formed in situ and oxidizes alcohol 39 first to the aldehyde via intermediate 42 and then to the carboxylic acid 10 via the aldehyde hydrate intermediate 43. 

Scheme 12.13 One-pot oxidation/epoxidation of allylic alcohols. (For experimental details see Chapter 8).

Immobilized TEMPO radical has also been used for one-pot oxidation of alcohols to carboxylic acids [14]. For this purpose TEMPO-resin 1 was combined with two... 

A -Isoxazolines exhibit considerable versatility in synthesis and one-pot oxidative ring contraction of stannyl oximes to A -isoxazolines with stereocontrol results from the strong directing effect of the tin group, followed by 1,3-dipolar cycloaddition (Scheme 26). In conjunction with other results, it was suggested that oximes with the stannyl group too far removed from the iminoxyl group (3-electton... 

As an extension, the same laboratory demonstrated the possibility of performing one-pot oxidative decarboxylations with concomitant iodina-tion when excess iodine was used (Scheme 16) [23]. As illustrated with the pipecolinic carbonate 26, this sequence can be performed followed by trapping of the iminium ion intermediate with 2-hexen-l-ol leading to the functionalized piperidine 27 in 71% yield. Subsequently, a 5-exo cyclization can be performed to give the bicyclic M,0-acetal 28, thus illustrating the potential of preparing complex systems in few steps. 

The oxidation of aromatic and aUphatic oximes and of tosylhydrazones on TS-1 with excess H2O2 was reported to regenerate corresponding aldehydes [141, 142]. These were obtained also by the one-pot oxidation of primary amines under analogous conditions [143]. 

Wacker oxidation One-pot oxidation of olefins to the corresponding ketones in the presence of catalytic amounts of Pd(ll)-salts 474... 

The first example of tandem oxidation and l,2-acetoxysulfenylation/l,2-disulfenylation of Baylis-Hillman (BH) alcohols was reported by Yadav et al. [20]. The reaction involves oxidation of BH alcohols with IBX in [bmim][Br] to give P-ketomethylene compounds, followed by Cul-imidazole catalyzed 1,2-acetoxy-sulfenylation with an organodisulfide and AcOH to afford vicinal acetoxysulfides in excellent yields with complete regioselectivity (Scheme 14.21). This reaction was tested in six different ionic liquid imidazolium salts. Among these ILs, [bmim][Br] dissolved IBX at room temperature and gave the best result in the one-pot oxidative reaction. After isolation of final products, the IL could be recycled for four times with up to 70% recovery and reused without any loss of efficiency. 

Yadav LDS, Awasthi C (2009) The first one-pot oxidative 1,2-acetoxysulfenylation and 1,2-disulfenylation of Baylis-HiUman alcohols in an ionic liquid. Tetrahedron Lett 50 3801-3804... 

This approach to bi-l,2,4-triazines has been extended by Wolihska to include a one-pot oxidation-hydrolysis sequence (09H(78)623), yielding the corresponding bi-l,2,4-triazinolate 42 (Scheme 15). This, in turn, can easily be converted into chloride 43, itself typically susceptible to displacement by primary and secondary amines. 

In a one-pot oxidation-heteroannulation process, pyrimidines 513 were synthesized from propargylic alcohols and benzamidine or acetamidines in the presence of o-iodoxybenzoic acid (IBX) or Mn02 under MWI conditions within 40 min (Scheme 99). The yields (61-84%) were higher than those (30-69%) after heating under reflux (03SL1443). 

Other sequential and one-pot oxidation-Wittig reactions have been reported using Swern, Dess-Martin, and barium permanganate oxidation. 

Polymer-supported sodium cyanoborohydride (PSCBH), now available commercially, has become more widely used. It is stable and effective even in the presence of oxidants, such as manganese dioxide, shown in this one pot oxidation-reduction amination protocol (eq 38). ... 

Shreeve and coworkers reported a convenient procedure for preparing (difluoroiodo)arenes by direct fluorination of the respective iodoarenes with the commercially available fluorinating reagent Selectfluor in acetonitrile solution. This procedure has been further improved by using the corresponding arene, elemental iodine and Selectfluor in a one-pot oxidative iodination/fluorination procedure [33]. 

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