Yamamoto epoxidation

General experimental procedure for Yamamoto epoxidation of homoallylic alcohols To a mixture of hydroxamic acid 21 (0.02 mmoi) and toiuene (0.25 mL) at room temperature was added VO(0/-Pr)3 (0.01 mmol). The mixture was stirred at room temperature for 8hours. After that time, 88% cumene hydroperoxide (1.5 mmol) was added, followed by homoallyhc alcohol (l.Ommol). The reaction mixture was stirred for 24 hours and then quenched by the addition of trimethyiphos-phite (1.5 mmol). The mixture was extracted with ethyi acetate. The combined organic layers were dried over Na2S04, filtered, and concentrated under reduced pressure. The crude product was purified by column chromatography on silica gei to give the desired epoxide. 

Yanagisawa, A. Yasue, K. Yamamoto. H. 7. Chem. Soc. Chem. Commun., 1994, 2103 Related Methods Ketones from Ethers and Epoxides (Section 174)... 

T. Iida, N. Yamamoto, N. Matsunaga, H.-G. Woo, M. Shibasaki, Enantioselective Ring Opening of Epoxides with 4-Methoxyphenol Catalyzed by Gallium Hetero-bimetallic Complexes An Efficient Method for the Synthesis of Optically Active 1,2-Diol Monoethers, Angew. Chem Int. Ed. EngL 1998,32 2223-2226. 

Ivie, G.W., Knox, J.R., Khalifa, S., Yamamoto, I., and Casida, J.E. Novel photoproducts of heptachlor epoxide, trans-chlordane, and trans-nomddot. Bull Environ. Contam. Toxicol, 7(6) 376-383, 1972. 

The reaction of superoxide ion with carbon tetrachloride is important for olefin epoxidations. This reaction includes the formation of the trichloromethyl peroxide radical Oj" + CCI4 —> Cl + CI3COO. The trichloromethyl peroxide radicals formed oxidize electron-rich olefins. The latter gives the corresponding epoxides. This peroxide radical is a stronger oxidizing agent than the superoxide ion itself (Yamamoto et al. 1986). 

In a recent paper, Zhang and Yamamoto have described a modified BHA ligand (235d) that is suitable for highly enantioselective vanadium-catalyzed epoxidation of homoallylic alcohols (Scheme 102). Both tram- and cA-substituted epoxides were achieved with nearly complete enantioselectivities and good yields. 

Maruoka K, Murase N, Ooi T, Yamamoto H (1991) A new cyclization of olefinic epoxides by modified organoaluminum reagents via epoxide rearrangement and subsequent intramolecular ene reaction. Synlett 857-858... 

Prior to the usage of the Ti-based catalytic system , the Sharpless group had reported their first asymmetric epoxidation of allylic alcohols using a combination of VO(acac)2/ TBHP and the chiral hydroxamic acid 67 (ee < 50%) or derivatives (ee 80%) ". In 1999, Yamamoto and coworkers described an improvement of this oxidation protocol, ee values up to 94%, by using hydroxamic acids derived from binaphthol, 68 being the... 

With a twist on the Sharpless asymmetric epoxidation protocol, Yamamoto and co-workers <99JOC338> have developed a chiral hydroxamic acid (17) derived from binaphthol, which serves as a coordinative chiral auxiliary when combined with VO(acac)j or VO(i-PrO)j in the epoxidation of allylic alcohols. In this protocol, triphenylmethyl hydroperoxide (TiOOH) provides markedly increased enantiomeric excess, compared to the more traditional t-butyl hydroperoxide. Thus, the epoxidation of E-2,3-diphenyl-2-propenol (18) with 7.5 mol% VO(i-PiO)3 and 15 mol% of 17 in toluene (-20 °C 24 h) provided the 2S,3S epoxide 19 in 83% ee. 

For a review of epoxide reduction with Bll<. see Cragg, Organoboranes in Organic Synthesis Marcel Dekkcr New York. 1973. pp. 345-348. See also Yamamoto Toi Sonoda Murahashi J. Chem. Soc., Chem. Commun. 1976, 672. 

Yamamoto has used the modularity of another type of oc-amino acid-based chiral ligand to promote enantioselective epoxidations of allylic alcohols [21]. Thus, as illustrated in Eq. (8), parallel libraries of various ligand candidates were prepared and the identity of the optimal ligand 13 was established through positional optimization. 

Wu in Comprehensive Asymmetric Catalysis I-III (Eds. Jacobsen, E. N. Pfaltz, A. Yamamoto H.), Springer, Berlin, 1999, p. 649f. (c) For organocatalytic asymmetric epoxidations, see chapter 10. 

Asao, N. Kasahara, T. Yamamoto, Y. o-n Chelation-controlled chemoselective ring openings of epoxides. Tetrahedron Lett. 2001, 42, 7903-7905. 

Miyamoto T., Yamamoto M., Ono A., Ohtani K. and Ando T. (1999) Substrate specificity of the epoxidation reaction in sex pheromone biosynthesis of the Japanese giant looper (Lepidoptera Geometridae). Insect Biochem. Mol. Biol. 29, 63-69. 

Yamamoto has reported that ytterbium triisopropoxide, prepared in situ from Yb(OTf)3 and LiOPr in THF, can be used in a very mild, highly efficient, and widely applicable procedure for the azidolysis of epoxides. In every case except styrene oxide, products are derived from the attack of azide at the less hindered carbon atom. The method appears to be quite tolerant of functionality, leaving preexisting tosyl, acyl, and siloxy groups intact (e.g.,... 

Preparation of the stereoisomers of the diepoxide pheromones represents more of a synthetic challenge, and it has been approached in several ways. As mentioned above, small quantities can be prepared in several steps from 3Z,6Z,9Z-trienes (Yamamoto et al., 1999 Yamazawa et al., 2001). First, nonselective partial epoxidation of 3Z,6Z,9Z-trienes,... 

Wakamura, S., Arakaki, N., Yamamoto, M., Hiradate, S., Yasui, H., Yasuda, T. and Ando, T. (2001b). Posticlure a novel trans-epoxide as a sex pheromone component of the tussock moth, Orgyia postica (Walker). Tetrahedron Lett., 42, 687-689. 

Tatsumi, T., Yamamoto, K., Tajima, H. and Tominaga, FI. (1992). Shape selective epoxidation of alkenes catalysed by polyoxometalate-intercalated hydrotalcite. Chem. Lett., 815. 

Katsuki T (1999) Epoxidation of allylic alcohols. In Jacobsen E, Pfaltz A, Yamamoto H (eds) Comprehensive asymmetric catalysis I—III. Springer, Berlin, Heidelberg, New York, p 621 f... 

Homoallylic alcohols can be asymmetrically epoxidized using a chiral vanadium catalyst equipped with the hydroxaraic acid ligand 45, as exemplified in Yamamoto s concise synthesis... 

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