Asymmetric oxidation reviews

Oxidations with Ru porphyrin complexes, both catalytic and stoicheiometric, have been reviewed [42, 45 7], as has the relatively fledgling subject of asymmetric oxidations catalysed by Ru porphyrin complexes [44],... 

In this review, we focus mainly on the preparative utility of organic peroxides, and only few mechanistic investigations are discussed. This review covers synthetic methodologies for the preparation of alkyl hydroperoxides and dialkyl peroxides (Section II) and the synthetic use of these peroxides in organic chemistry (Section III). In Section II, general methods for the synthesis of organic hydroperoxides and dialkyl peroxides are discussed, as well as the preparation of enantiomerically pure chiral hydroperoxides. The latter have attracted considerable interest for asymmetric oxidation reactions during the last years. 

For an excellent review on asymmetric oxidation of sulfides see Reference 191. 

Chiral sulfoxides (12, 92). Kagan et al.3 have reviewed the asymmetric oxidation of sulfides by a water-modified Sharpless reagent. Optical yields are generally highest in the oxidation of aryl methyl sulfides (—75-90%). 

The research work of recent years includes predominantly the epoxidation of alkenes9,200, asymmetric hydroxylations209,224-228 and the asymmetric oxidation of sulfides to sulfoxides205,209,229,230. Optical yields of practical significance were obtained (>90%). A detailed review published in 1991231 reports about the versatile use of oxaziridines in the field of the electrophilic amination. 

Finally, it is very important to note that more sophisticated catalysts have been prepared either by introducing bulky and/or chiral substituent on the meso-aryl or pyrrole rings [for recent reviews see, for instance, 36,56e,56f,63] or by inserting the metalloporphyrin into various polymeric materials [64-75, for recent reviews see also 76], These results have shown that this was a good strategy not only toward asymmetric oxidation catalysts, but also toward more regioselec-tive and/or efficient and stable catalysts. 

Reviews on asymmetric oxidation reactions (a) A.K. Yudin, Aziridines and Epoxides in Organic Synthesis, Wiley-VCH, Weinheim, 2006 (b)... 

Not many catalyzed processes involving free radicals are known with these metals. Some vanadium-catalyzed pinacol coupling reactions were developed (reviews [129, 171], [172, 173] and cited ref, [174]). Niobium and tantalum complexes were applied in pinacol coupling reactions [130]. Vanadium(IV) [175-179] and vanadium(V) ([129], reviews [180-186]) complexes are known to catalyze asymmetric oxidative dimerizations of phenols and naphthols in moderate to excellent ees applying oxygen as the terminal oxidant. Biaryls are accessible by intramolecular coupling of sodium tetraarylborates, catalyzed by EtOVOCl2 in the presence of air [187]. 

The focus is on proteins with redox functionalities hke oxidases, mono- and dioxygenases, and other enzymes able to utilize molecular oxygen as an oxidant, but dehydrogenases and peroxidases will also be discussed. The use of common proteins such as bovine serum albumin with no distinctive redox functionalities as chiral templates for asymmetric oxidations has been reviewed elsewhere [16]. As the oxidations require the transfer of electrons from a substrate to an electron... 

If the optically active organoselenium compounds can be used for Tomoda s or Tiecco s catalytic system using diselenide and persulfate (see Sect. 4.1), a catalytic asymmetric oxidation reaction should be possible. The enantioselectivity of the produced allylic compounds may depend on the stereoselectivity of the oxyselenenylation step of chiral selenium electrophiles with prochiral alkenes. Several groups have reported diastereoselective oxyselenenylation using a variety of chiral diselenides in moderate to high diastereoselectivity [5 f, g, i, 25]. The detailed results are reviewed in Chap. 2. 

For oxidation reactions, the cinchona alkaloids have been mainly employed to control the osmium-catalyzed conversion of an alkene to give a 1,2-diol or vicinal functionalized alcohol. As these are important asymmetric reactions, they have been the subject of a number of reviews [1-18]. This chapter discusses the uses of these alkaloids as chiral ligands in asymmetric oxidation reactions. Oxidation reactions where an alkaloid is used in a phase-transfer sense are discussed in Chapter 5. 

This chapter summarizes several types of asymmetric oxidation reactions. Since most of the these reactions have been thoroughly reviewed, coverage is selective. Once again, the emphasis is on utility and rationales of stereoselectivity. 

A great deal of effort has been expended in the development of ways to carry out the asymmetric oxidation of sultides to sulfoxides progress in this field has been exhaustively reviewed [114], This is interesting from th a theoretical viewpoint and from the utility of certain chiral sulfoxides as reagents in asymmetric synthesis [115]. Some natural products also contain sulfoxide stereogenic centers. 

Meunier has reviewed recent advances in asymmetric oxidation. Jacobsen s asymmetric epoxidation catalysts are some of the most successful. These use Mn(III) in a chiral salen ligand with NaOCl as primary oxidant. The intermediacy of Mn(V) 0x0 species has been proposed as the active species formed after O atom transfer from the hypochlorite. Enantiomeric excesses of 97-98% are seen in the epoxide product on a consistent basis across a wide variety of alkene substrates. 

E. N. Jacobsen, in Comprehensive Organometalhc Chemistry II A Review of the Literature 1982-1994 , Eds. E. W. Abel, R G. A. Stone, G. Wilkinson, Pergamon Press, Oxford, U.K., 1995, Vol. 12, 1097-1136 (Transition Metal-Catalyzed Oxidations Asymmetric Epoxidatioriy, T. Katsuki, Coord. Chem. Rev. 1995,140, 189-214 (Catalytic Asymmetric Oxidations Using Optically Active (Salen)Manganese(lll) Complexes as Catalysts), B. M. Trost, C. Heinemann, X. Ariza, S. Weigand, J. Am. Chem. Soc. 1999, 121, 8667. 

A comprehensive review (260 refs.) on the synthesis of carbohydrates from noncarbohydrate sources covers the use of benzene-derived diols and products of Sharpless asymmetric oxidation as starting materials, Dodoni s thiazole and Vogel s naked sugar approaches, as well as the application of enzyme-catalysed aldol condensations. The preparation of monosaccharides by enzyme-catalysed aldol condensations is also discussed in a review on recent advances in the chemoenzymic synthesis of carbohydrates and carbohydrate mimetics, in parts of reviews on the formation of carbon-carbon bonds by enzymic asymmetric synthesis and on carbohydrate-mediated biochemical recognition processes as potential targets for drug development, as well as in connection with the introduction of three Aldol Reaction Kits that provide dihydroxyacetone phosphate-dependent aldolases (27 refs.). A further review deals with the synthesis of carbohydrates by application of the nitrile oxide 1,3-dipolar cycloaddition (13 refs.). ... 

For a recent review on asymmetric oxidative coupling of 2-naphthols and their derivatives H. Wang, Chirality, 2010,22, 827. 

Asymmetric oxidations of sulfides in water have been obtained by carrying out the reaction in the presence of cyclodextrin (CD). The solvent effect, the oxidizing agent and the nature of the sulfide have been widely investigated [52] and reviewed [53]. Sulfides are oxidized selectively to sulfoxides. The reaction yields are generally good but the enantiomeric excesses are rarely acceptable if compared with those obtained with other procedures. The best... 

Oxidation reactions make up an important class of organocatalyzed asymmetric processes, offering some of the most synthetically useful and widely apphcable methods to have emerged from the field [1, 2]. In this chapter we review a subsection of this area, namely, covalently activated organocatalytic asymmetric oxidation reactions. Here, covalent activation will be considered as the catalytic activation of the stoichiometric oxidant through the formation of new covalent bonds between the oxidant and the catalyst. Key developments prior to a similar review [2] are summarized, along with a more detailed account of advances since 2006. Prolinol-and imidazolidinone-catalyzed oxidation reactions, where the substrate rather than the oxidant may be covalently activated, are covered elsewhere in this publication (Chapters 2 and 3). 

HP as the oxygen source, have been reviewed, with major focus on the their synthetic potential. Recent experimental investigations of the nature of catalytically active species and mechanisms of their action are summarized.Asymmetric oxidation reactions, viz., sulfoxidation, epoxidation, dihydroxylation, and aminohydroxylation in water have been reviewed. The focus is on the development of catalytic oxidation in water, particularly the use of HP in the presence of metal catalysts. The enantioselective oxidation of sulfides to sulfoxides is also included. ... 

Much effort has been placed in the synthesis of compounds possessing a chiral center at the phosphoms atom, particularly three- and four-coordinate compounds such as tertiary phosphines, phosphine oxides, phosphonates, phosphinates, and phosphate esters (11). Some enantiomers are known to exhibit a variety of biological activities and are therefore of interest Oas agricultural chemicals, pharmaceuticals (qv), etc. Homochiral bisphosphines are commonly used in catalytic asymmetric syntheses providing good enantioselectivities (see also Nucleic acids). Excellent reviews of low coordinate (coordination numbers 1 and 2) phosphoms compounds are available (12). 

The Sharpless-Katsuki asymmetric epoxidation (AE) procedure for the enantiose-lective formation of epoxides from allylic alcohols is a milestone in asymmetric catalysis [9]. This classical asymmetric transformation uses TBHP as the terminal oxidant, and the reaction has been widely used in various synthetic applications. There are several excellent reviews covering the scope and utility of the AE reaction... 

The past thirty years have witnessed great advances in the selective synthesis of epoxides, and numerous regio-, chemo-, enantio-, and diastereoselective methods have been developed. Discovered in 1980, the Katsuki-Sharpless catalytic asymmetric epoxidation of allylic alcohols, in which a catalyst for the first time demonstrated both high selectivity and substrate promiscuity, was the first practical entry into the world of chiral 2,3-epoxy alcohols [10, 11]. Asymmetric catalysis of the epoxidation of unfunctionalized olefins through the use of Jacobsen s chiral [(sale-i i) Mi iln] [12] or Shi s chiral ketones [13] as oxidants is also well established. Catalytic asymmetric epoxidations have been comprehensively reviewed [14, 15]. 

The study of optical isomers has shown a similar development. First it was shown that the reduction potentials of several meso and racemic isomers were different (Elving et al., 1965 Feokstistov, 1968 Zavada et al., 1963) and later, studies have been made of the ratio of dljmeso compound isolated from electrolyses which form products capable of showing optical activity. Thus the conformation of the products from the pinacolization of ketones, the reduction of double bonds, the reduction of onium ions and the oxidation of carboxylic acids have been reported by several workers (reviewed by Feokstistov, 1968). Unfortunately, in many of these studies the electrolysis conditions were not controlled and it is therefore too early to draw definite conclusions about the stereochemistry of electrode processes and the possibilities for asymmetric syntheses. 

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