Catalytic Asymmetric Dihydroxylation of C,C Double Bonds with Osmium Tetroxide Using Selenoxides as Co-oxidants

Krief, Alain; Colaux, Catherine

doi:10.1055/s-2001-12437

Cited by 20 publications

(8 citation statements)

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“…In fact, it has been noted by Sharpless and co-workers that with carbamate nitrogen sources regioselectivity of the B isomer is inversely correlated with enantiselectivity 3a. We now report a method utilizing pH control to override other variables in the AA reaction of styrenes to selectively provide the B regioisomer with good enantiomeric ratios (ers) 1 …”

mentioning

confidence: 95%

The Use of pH to Influence Regio- and Chemoselectivity in the Asymmetric Aminohydroxylation of Styrenes

Nesterenko¹,

Byers²,

Hergenrother³

2003

Org. Lett.

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[reaction: see text] The pH-controlled Sharpless asymmetric aminohydroxylation (AA) of styrenes provides 1-aryl-2-amino ethanols (regioisomer B) with high enantio-, chemo-, and regioselectivity. As existing AA protocols typically give regioisomer A as the major reaction product when using carbamate nitrogen sources, this method is a convenient alternative for the selective production of regioisomer B.

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mentioning

confidence: 95%

The Use of pH to Influence Regio- and Chemoselectivity in the Asymmetric Aminohydroxylation of Styrenes

Nesterenko¹,

Byers²,

Hergenrother³

2003

Org. Lett.

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“…We have previously reported highly enantioselective reactions of α-thio carbanions derived from benzyl phenyl and pyridyl sulfides, which were proven to proceed through different resolution pathways, i.e., dynamic kinetic resolution for the former carbanion and dynamic thermodynamic resolution for the latter. , These results showed that pivotal resolution pathways can be chosen by changing the substituent on the sulfur. Hoffmann and co-workers have reported that α-seleno carbanions are more configurationally stable than α-thio carbanions but less stable than α-oxy carbanions. , Since chiral selenides have the potential to be asymmetric catalysts , and synthetic intermediates, , it is important to develop the highly enantioselective reaction of α-seleno carbanions and to clarify the reaction pathways in more detail. , We now report enantioselective reactions of α-lithio benzyl phenyl selenide and α-lithio benzyl 2-pyridyl selenide with electrophiles in the presence of an external chiral ligand (Scheme ), including the reaction mechanism, on the basis of Beak's test using a deficient amount of the electrophile and the warm-cool procedure 14a-c together with the analysis of the data obtained by the MO calculation. We also report a highly enantioselective olefination involving the enantioselective reaction of the α-seleno carbanion with 4-substituted cyclohexanones and the subsequent stereospecific elimination reaction …”

Section: Introductionmentioning

confidence: 88%

Highly Enantioselective Reaction of α-Selenoorganolithium Compounds with Chiral Bis(oxazoline)s and Preparation of Enantioenriched Benzylidencyclohexanes

et al. 2004

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The enantioselective reaction of alpha-seleno carbanions derived from bis(phenylseleno)acetal and bis(2-pyridylseleno)acetal in the presence of bis(oxazoline)s with various electrophiles gave products with high enantioselectivity. The enantioselective reaction of alpha-lithio benzyl 2-pyridyl selenide gave the products with stereochemistry reverse to that obtained in the reaction of alpha-lithio benzyl phenyl selenide. Mechanistic investigation suggests the enantiodetermination of these reactions at -78 degrees C depends on dynamic thermodynamic resolution. The enantioselective reaction was applied to the preparation of enantioenriched olefins and epoxide.

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“…Methyltrioxorhenium can be used in place of the flavin mimic [96], as can tungsten(VI) [97] and carbon dioxide [98]. Other alternatives for the oxidant for stoichiometric oxidations include the use of a selenoxide [99], including a photochemical oxidation of catalytic selenium [100], iodine [101], sodium chlorite [102], hypochlorite [103], and electrochemical methods [101,104]. Even air can be used as the oxidant [99,100], but care has to be taken with regard to the choice of solvent as cleavage of the product 1,2-diol can occur, especially when the alkene has an aryl substituent [53,105,106].…”

Section: Bisalkaloid Ligandsmentioning

confidence: 99%

Cinchona Alkaloids as Chiral Ligands in Asymmetric Oxidations

Ager¹

2009

Cinchona Alkaloids in Synthesis and Catalysis

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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][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][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.The use of osmium tetroxide for the conversion of an alkene to a 1,2-diol is a wellestablished reaction [19][20][21][22]. The formation of an intermediate cyclic ester accounts for the cis-stereochemistry [21, 23-32] as reaction occurs on the least hindered face of the alkene [21,30,[33][34][35][36][37][38]. This steric effect is amplified in cyclic substrates [39,40]. The reaction conditions have to be carefully controlled to avoid oxidative cleavage of the diol product [28].There is a marked rate acceleration in the presence of a tertiary amine or pyridine [19,41]. This finding provided the background for the asymmetric dihydroxylation (AD) and, later, the asymmetric aminohydroxylation (AA) reactions as it is this ligand acceleration effect (LAE) that ensures the reaction pathway involving the ligand.The use of a cooxidant can reduce the amount of osmium required for a complete reaction of an alkene from stoichiometric to catalytic; some examples of oxidants that can achieve this are peroxides [20,22,35,37,[42][43][44] including hydrogen peroxide [20,42], chlorates [45], periodate [46,47], hypochlorite [48], N-methylmorpholine-N-oxide (NMMO) [22,34,35,37,49], potassium ferricyanide [50,51], and even air [52,53].Stereoselection for the OsO 4 reactions itself can also be observed when a directing group is adjacent to the alkene, such as in an allyl alcohol. An empirical rule has been devised, where the reagent approaches from the face opposite to the preexisting oxygen functionality. Although the hydroxy group may be protected, the presence of an acyl group reduces stereoselectivity. cis-Alkenes afford better selectivity

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Catalytic Asymmetric Dihydroxylation of C,C Double Bonds with Osmium Tetroxide Using Selenoxides as Co-oxidants

Cited by 20 publications

References 1 publication

The Use of pH to Influence Regio- and Chemoselectivity in the Asymmetric Aminohydroxylation of Styrenes

The Use of pH to Influence Regio- and Chemoselectivity in the Asymmetric Aminohydroxylation of Styrenes

Highly Enantioselective Reaction of α-Selenoorganolithium Compounds with Chiral Bis(oxazoline)s and Preparation of Enantioenriched Benzylidencyclohexanes

Cinchona Alkaloids as Chiral Ligands in Asymmetric Oxidations

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