Dihydroxylation with hydrogen peroxid

R 117 M.M. Abu-Omar, G.S. Owens and A. Durazo, Catalytic Olefin Epoxida-tion and Dihydroxylation with Hydrogen Peroxide in Common Ionic Liquids Comparative Kinetics and Mechanistic Study , p. 277 Vol. 857,2003 Beyond Metallocenes... 

In the presence of chiral ligand (DHQD)2PHAL, high enantioselectivity was obtained in the dihydroxylation with hydrogen peroxide (Figure 8.2) [131]. 

Dihydroxylation of the allyl groups of (70) with hydrogen peroxide and catalytic osmium tetroxide, followed by 0-nitration of the product (72), yields the hexanitrate ester (73). Similar treatment of the mono-allyl ether (74) affords the pentanitrate ester (76). Evans and Callaghan also 0-nitrated the hydroxy groups of (70) and (74) to yield the dinitrate and trinitrate esters, (71) and (75), respectively. The dinitrate ester (71) may find use as a monomer for the synthesis of energetic binders. 

Cyclic osmic esters have long been known to be involved in the osmium tetroxide-catalyzed cis-dihydroxylation of alkenes, but not arenes. The isolation of compound (18) by Wallis and Kochi following irradiation of the charge-transfer complex between osmium tetroxide and benzene is therefore of particular interest. This suggests that the corresponding use of catalytic quantities of osmixim tetroxide in conjunction with hydrogen peroxide could lead to the formation of polyhydroxylated cyclohexenes and -anes. 

Tan, H., and I.H. Espenson, Kinetics and Mechanism of the Dihydroxylation and Epoxidation of Conjugated Dienes with Hydrogen Peroxide Catalyzed by Methyhhenium Trioxide, Inorg. Chem. 37 467-472 (1998). 

Since Os04 is volatile, toxic and expensive, considerable effort has been devoted to the catalytic application of the cis dihydroxylation of alkenes in the presence of excess cooxidant.57-290 Previous procedures used metal chlorate (Hoffman reagent),339 or hydrogen peroxide (Milas reagent)350 as cooxidant, usually in Bu OH or acetone.290 Recent procedures utilize t-butyl hydroperoxide in conjunction with ammonium salts (Et4NOH or Et4NOAc)57,351 or N-methylmorpholine N-oxide,352 and are generally more selective. 

Inclusion in the reaction of a cooxidant serves to return the osmium to the osmium tetroxide level of oxidation and allows for the use of osmium in catalytic amounts. Various cooxidants have been used for this purpose historically, the application of sodium or potassium chlorate in this regard was first reported by Hofmann [7]. Milas and co-workers [8,9] introduced the use of hydrogen peroxide in f-butyl alcohol as an alternative to the metal chlorates. Although catalytic cis dihydroxylation by using perchlorates or hydrogen peroxide usually gives good yields of diols, it is difficult to avoid overoxidation, which with some types of olefins becomes a serious limitation to the method. Superior cooxidants that minimize overoxidation are alkaline t-butylhydroperoxide, introduced by Sharpless and Akashi [10], and tertiary amine oxides such as A - rn e t h y I rn o r p h o I i n e - A - o x i d e (NMO), introduced by VanRheenen, Kelly, and Cha (the Upjohn process) [11], A new, important addition to this list of cooxidants is potassium ferricyanide, introduced by Minato, Yamamoto, and Tsuji in 1990 [12]. 

However, since the catalytic system is homogenous, carefully adjusted reaction conditions were needed to circumvent the second nonselective catalytic cycle. Slow addition of the alkene and the hydrogen peroxide was necessary to obtain good enantioselectivities (Table 6) [13]. Recently, Backvall s group reported that the Cinchona alkaloid ligand participated in the reoxidation process and took the role of NMO in the catalytic cycle [15]. Versions of the triple catalytic system with vanadyl acetylacetonate replacing the flavin analogue [16] or m-CPBA as the terminal oxidant [17] have been developed and successfully applied to racemic dihydroxylation reactions. 

Quite recently it was reported that in addition to hydrogen peroxide, periodate or hexacyanoferrat(III), molecular oxygen21,31-34 can be used to reoxidize these metal-oxo compounds. New chiral centers in the products can be created with high enantioselectivity in the dihydroxylation reactions of prochiral alkenes. The development of the catalytic asymmetric version of the alkene dihydroxylation was recognized by Sharpless receipt of the 2001 Nobel prize in Chemistry. 

Recently, 3,5-bis(trifluoromethyl)benzeneseleninic acid has been used in a tandem catalytic epoxidation." The concept of tandem catalysis has been applied to oxidation reactions by Backvall and co-workers for the direct dihydroxylation of olefins using a couple catalytic system and hydrogen peroxide as the terminal oxidant." In this context, the seleninic acid was used in combination with a trifluoromethyl oxaziridine catalyst (Scheme 17), using urea hydrogen peroxide as the terminal oxidant." This system showed... 

Many different co-oxidants can be used in conjunction with osmium tetroxide for the catalytic dihydroxylation reaction. The most popular is A -methylmorpholine N-oxide (NMO) the use of NMO with less than one equivalent of osmium tetroxide is often referred to as the Upjohn conditions. Other oxidants, such as [K3Fe(CN)6], tert-hutyl hydroperoxide, hydrogen peroxide or bleach are effective. In these reactions, the intermediate osmate ester is oxidized to an osmium(VIII) species that is then hydrolysed with regeneration of osmium tetroxide to continue the cycle. For example, less than 1 mol% of osmium tetroxide is needed for the dihydroxylation of the alkene 74 (5.80). 

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