Catalytic asymmetric oxidation

Table 8.2 shows the results of the cross-coupling reaction between two differently substituted 2-naphthol derivatives using the CuCl-(5)Phbox catalyst. In conclusion, the first catalytic asymmetric oxidative coupling with a high cross-coupling selectivity was accomplished under mild conditions. 

Colonna S, Del Sordo S, Gaggero N, Carrea G, Pasta P (2002) Enzyme-Mediated Catalytic Asymmetric Oxidations. Heteroatom Chem 13 467... 

Asymmetric Oxidations Catalytic asymmetric oxidation of sulfides has attracted great interest in recent decades. The field is dominated by use of titanium, manganese and vanadium complexes, and examples of the use of iron catalysts are less common. The challenging asymmetric oxidation of sulfides with non-heme iron catalysts has been achieved with success in a few cases. 

A catalytic asymmetric oxidation of mono-, di-, and tri-substituted alkenes using a chiral bishydroxamic acid (BHA) complex of molybdenum catalyst in air at room temperature leads to good to excellent selectivity. It has been suggested that the Mo-BHA complex combines with the achiral oxidant to oxidize the alkene in a concerted fashion by transfer of oxygen from the metal peroxide to the alkene.78 The chiral BHA-molybdenum complex has been used for the catalytic asymmetric oxidation of sulfides and disulfides, utilizing 1 equiv. of alkyl peroxide, with yields up to 83% and ees up to 86%. An extension of the methodology combines the asymmetric oxidation with kinetic resolution providing excellent enantioselectivity (ee = 92-99%).79... 

A recent systematic study of the role played by titanium alkoxide, 2-propanol, and molecular sieves (MS) has permitted the development of an efficient catalytic system furnishing chiral sulfoxides with high ee.54 This catalyst has a new composition Ti(0-i-Pr)4/(/ ,/ )-DET/i-PrOH (1 / 4 / 4), in the presence of 4A MS, which is a combination of the Modena47 and Sharpless systems. Using this new system, the Orsay group achieved the highest enantioselectivity in catalytic asymmetric oxidation of sulfides by a nonenzymatic method (Table 8). 

In addition to the enantioselective preparation of 1,3-dithiane 1 -oxides, our group has been concerned with the development of novel methods for the catalytic asymmetric oxidation of other prochiral sulfides our currently preferred system employs an enantiomerically pure sulfonylimine and commercially available hydrogen peroxide.70... 

The introduction of catalytic oxidations using oxygen from air is of much interest and breakthrough discoveries and spectacular progress have been achieved in research on catalytic asymmetric oxidations since the early part of the last century [3-5]. The increased number of publications per year in this area, as extracted from the electronically accessible literature in a SciFinder search, is shown in Figure... 

Figure 20.1 Historical development of the number of publications on catalytic asymmetric oxidation.

This catalytic asymmetric oxidation yielded J -methylphenylsulfoxide with a productivity of30g/l/day andane.e. >98% [35]. Chloroperoxidase is the most versatile peroxidase with better stability compared to other peroxidases, because spontaneous oxidation can be suppressed in the presence of ascorbic acid or dihydroxyfu-maric acid, and with better enantioselectivity because substrate access to the heme iron and ferryl oxygen favors stereoselective oxygen transfer [36]. Chloroperoxidase has been used for catalyzing the oxidation of cis-cydopropylmethanols with much higher enantioselectivity than trans-isomers [37]. 

Colonna, S., Del Sordo, S., Gaggero, N., Carrea, G. and Pasta, P. (2002) Enzyme-mediated catalytic asymmetric oxidations. Heteroatom Chemistry, 13, 467 73. 

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. 

The highest diastereoselectivity of asymmetric methoxyselenenylation of alkenes was achieved using the ferrocenylselenium triflates in excellent chemical yields [5gj. For example, the stoichiometric reaction of the chiral ferrocenylselenium triflate 41, prepared from the chiral diferrocenyl diselenide 2, with traus- -methylstyrene afforded the corresponding methoxyselenenylated product in high chemical yield with excellent diastereoselectivity (up to 98 % de). Fukuzawa and co-workers employed the diferrocenyl diselenide 2 for the catalytic asymmetric oxidation of, y-unsaturated esters and traus- -methylstyrene to the corresponding optically active allylic methyl ethers with moderate enantio-selectivity (Scheme 24) [27]. The allylic ethers were produced from 4-phenyl-3-butenoic acid esters in 70-78% yield with 17-22% ee. 

Cogan, D. A. Liu, G. Kim, K. Backes, B. J. Ellman, J. A., Catalytic Asymmetric Oxidation of fert-Butyl Disulfide. Synthesis of tert-Butanesulfinamides, terf-Butyl Sulfoxides, and fert-Butane-sulfmimines / Am. Chem. Soc. 1998, 32, 8011. 

T. Katsuki, Catalytic asymmetric oxidations using optically active (salen)manganese(in) complexes as catalysts. Coord. Chem. Rev. 140 (1995) 189. 

Y. Ferrand, R. Daviaud, P. Le Maux, G. Simonneaux, Catalytic asymmetric oxidation of sulfide and styrene derivatives using macroporous resins containing chiral metalloporphyrins (Fe, Ru), Tetrahedron Asymmetry 17 (2006) 952. 

When (R)-binaphtol 3.7 (R = H) is used as a titanium ligand, the catalytic asymmetric oxidation of arylmethylsulfides by fe/7-BuOOH in the presence of water in CCI4 leads to (i )-sulfbxides [815, 947, 1514], In tins reaction, the initial oxidation of the sulfide into the chiral sulfoxide takes place with a moderate ee (= 50%). This step is fbllowed by further oxidation of the sulfoxides with kinetic resolution ( 1.6) [815, 1514]. To observe a high enantiomeric excess (> 90%), it is necessary to oxidize the minor (S)-enantiomer into the corresponding sulfone, and the chemical yield of the sulfoxide is in the 45 - 65% range. 

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. 

Kita and coworkers developed a catalytic asymmetric oxidation using iodoxybenzene in a cationic reversed micellar system in the presence of chiral tartaric acid derivatives. Under these conditions, sulfides 824... 

Based on their mechanistic investigation on the Cu -mediated oxidative coupling of 2-naphthol derivatives, Smrcina, Kocovsky, and co-workers were able to develop the first catalytic asymmetric oxidative biaryl coupling reaction (Scheme 3.3). AgCl was used as the stoichiometric oxidant to regenerate the Cu species. In order to avoid the formation of detrimental HCl by-product, the corresponding sodium 2-naphthol salts were employed as the coupling partners. The desired product 3 was obtained in 41% yield (8 turnovers) with 32% ee. 

Scheme 3.3 The first catalytic asymmetric oxidative biaryl coupling reaction reported by Smrcina and Kocovsky.

The catalytic asymmetric oxidation of prochiral sulfides by chemical means is a difficult task. While a number of workers have been active in this area during the past few years, few systems simultaneously show good induction of chirality and good catalytic activity. The most common catalysts involve transition-metal complexes (homogeneous or supported) as well as chiral electrodes. These approaches are described successively below. 

Scheme 7.35 Rueping s catalytic asymmetric oxidative iminium domino reactions.

Suzuki T, Morita K, Matsuo Y, Hiroi K (2003) Catalytic asymmetric oxidative lactonizations of meso-diols using a chiral iridium complex. Tetrahedron Lett 44 2003-2(X)6... 

Developments, since 2000, in catalytic asymmetric oxidations and related reactions using O2 or H2O2 as conventional oxidants have been summarized. ... 

A suitably designed chiral analog of NHPI can be used as an enantioselective oxidation catalyst. Einhorn reported the synthesis of axially chiral NHPI analogs (Scheme 6.21). These NHPI derivatives can be used in several catalytic asymmetric oxidation reactions, such as indane oxidation and oxidative deprotection of acetal. 

Water is the medium where all biological reactions take place, including oxidation reactions, but it is a rather unfamiliar solvent for chemists who tend to avoid it, often in an over-prudent approach. When H2O2 and O2 are used as oxidants, water is present as a by-product and this prompted the investigation of catalytic asymmetric oxidation reactions in water. The hydrophobic effect, which consists of the tendency for organic species to self-assemble in water, is the most peculiar effect of this solvent and operates both on apolar catalysts and organic substrates. This overall "squeeze out" effect produces, in several cases, positive effects on both the catalytic activity and the enantioselectivity of asymmetric reactions, as described in the following examples of stereoselective oxidation. 

Fujisaki, J., Matsumoto, K., Matsumoto, K., et al. (2011). Catalytic Asymmetric Oxidation of Cychc Dithioacetals highly Diastereo- and Enantioselective Synthesis of the S-oxides by a Chhal Aluminum(salalen) Complex, J. Am. Chem. Soc., 133, pp. 56-61. 

SCHEME 6 Gong s catalytic, asymmetric oxidative dimerization of naphthols using vanadium complex 35. Reboot of viriditoxin/pigmentosin A S5mthetic plan. 

Palucki M, Finney NS, PospisU PJ, Giiler ML, Ishida T, Jacobsen EN. Catalytic asymmetric oxidations using opticaUy-active (salen)manganese(III) complexes as catalysts. J Am Chem Soc 1998 120 948-54. 

Cogan DA, Liu GC, Kim KJ et al (1998) Catalytic asymmetric oxidation of tert-butyl disulfide. S5mthesis of tert-butanesulfinamides, tert-butyl sulfoxides, and tert-butanesulfinimines. J Am Chem Soc 120 8011-8019... 

Thanks to its efficiency, selectivity, operational simplicity, and use of economic and largely available components, the SAE has been the most important catalytic asymmetric oxidation reaction implemented in several asymmetric syntheses. In the following section, relevant examples of SAE will be discussed first in the preparation of natural products, followed by examples of SAE in pharmaceutical drugs synthesis. 

Matsugi M, Fukuda N, Muguruma Y, Yamaguchi T, Minami-kawa J-I, Otsuka S. Catalytic asymmetric oxidation of sulfide with titanium-mandelic acid complex practical synthesis of (S)-3-[l-(2-methylphenyl)imidazol-2-ylsulfinyl]propan-l-ol, the key intermediate of OPC-29030. Tetrahedron 2(X)1 57 2739-2744. 

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