Asymmetric Catalysis with Water: Efficient Kinetic Resolution of Terminal Epoxides by Means of Catalytic Hydrolysis

Tokunaga, Makoto; Larrow, Jay F.; Kakiuchi, Fumitoshi; Jacobsen, Eric N.

doi:10.1126/science.277.5328.936

Cited by 1,311 publications

(549 citation statements)

References 15 publications

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“…32 In addition to diamide ligands, we also explored the use of ferrocene-derived Schiff base metal complexes for the ring-opening polymerization of cyclic esters. 17,[33][34][35][36] Schiff base metal complexes have found numerous uses in coordination chemistry and catalysis, [37][38][39][40][41][42] alkoxide yttrium complexes supported by such ligands being intensely researched as initiators for the ring-opening polymerization of cyclic esters. 17,[35][36][43][44][45][46][47][48][49][50] On the other hand, reports of structurally characterized alkyl or aryl rare earth complexes bearing an imine functionality in the backbone are rare, [51][52] the majority being represented by phosphinimine ligands.…”

Section: Introductionmentioning

confidence: 99%

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

Brosmer

Diaconescu

2015

Organometallics

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The synthesis and characterization of two yttrium alkyl complexes supported by a bisphosphinimine ferrocene ligand, NP by NMR spectroscopy, electrochemical measurements, and elemental analysis. Reactivity studies were also carried out, however, the lack of prolonged thermal stability at ambient temperature of these molecules led to decomposition before the clean formation of reaction products could be observed.1

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Section: Introductionmentioning

confidence: 99%

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

Brosmer

Diaconescu

2015

Organometallics

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“…Styrene oxides are extremely useful and can be prepared by a number of methods such as asymmetric reduction of ␣-halo acetophenones (refs. 11 and 12 and references therein), asymmetric dihydroxylation of styrenes (13,14), and kinetic resolution of racemic epoxides (15). The asymmetric epoxidation of styrenes also has received a considerable amount of interest.…”

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confidence: 99%

Highly enantioselective epoxidation of styrenes: Implication of an electronic effect on the competition between spiro and planar transition states

Hickey

Goeddel

Crane

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Asymmetric epoxidation of various styrenes using carbocyclic oxazolidinone-containing ketone 3 has been investigated. High enantioselectivity (89 -93% enantiomeric excess) has been attained for this challenging class of alkenes. Mechanistic studies show that substituents on the ketone catalyst can have electronic influences on secondary orbital interactions, which affects the competition between spiro and planar transition states and, ultimately, enantioselectivity. The results described herein not only reveal the potential of chiral dioxirane catalyzed asymmetric epoxidation as a viable entry into this important class of olefins but also further enhance the understanding of the mechanistic aspects of chiral ketone-catalyzed asymmetric epoxidation. Epoxides are important intermediates for the synthesis of complex molecules. Asymmetric epoxidation of prochiral alkenes presents a powerful strategy for the synthesis of enantiomerically enriched epoxides. Great progress has been made in the areas of asymmetric epoxidation of allylic alcohols (1-3), chiral metal complex-catalyzed epoxidation of unfunctionalized alkenes (particularly with conjugated cis-and trisubstituted alkenes) (4 -7), and asymmetric epoxidation of electron-deficient alkenes under nucleophilic conditions (8 -10). Styrene oxides are extremely useful and can be prepared by a number of methods such as asymmetric reduction of ␣-halo acetophenones (refs. 11 and 12 and references therein), asymmetric dihydroxylation of styrenes (13,14), and kinetic resolution of racemic epoxides (15). The asymmetric epoxidation of styrenes also has received a considerable amount of interest. Various chiral catalysts and reagents have been investigated for the epoxidation of styrenes, including chiral porphyrin complexes (16 -34), chiral salen complexes (35-42), chiral oxaziridines and oxaziridinium salts (43-46), and enzymes (47-51). Metal catalysts such as chiral porphyrin and salen complexes have been studied extensively for the epoxidation of these alkenes, and the enantioselectivities have reached the 80% range in a number of cases (21,23,29,31,37,38,40,41), with 96% enantiomeric excess (ee) being obtained in one case (3,5-dinitrostyrene) (23).Among other oxidants, dioxiranes either isolated or generated in situ are powerful epoxidation agents (Scheme 1; refs. 52-54). Chiral dioxiranes were shown recently to be effective for asymmetric epoxidation of trans-, trisubstituted (55-91), and certain cis-alkenes (92-95). Asymmetric epoxidation of styrenes with chiral dioxiranes has been studied also (61,66,68,81,88,90,(93)(94)(95); however, the enantioselectivity has not exceeded 85% (93-95). Generally speaking, the highly enantioselective epoxidation of styrenes still remains a formidable challenge.During our studies, we found that varying the catalyst structure could have a dramatic effect on enantioselectivity for the dioxirane-mediated epoxidation of styrene. Fructosederived ketone 1 (Scheme 2), a very effective catalyst for transand trisubstituted alkenes, gave only 24...

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“…The Jacobson method [14,15] for obtaining a diol from a terminal alkene via preparation of the racemic epoxide was not considered because of the susceptibility of the sulfide to oxidation during the epoxidation reaction.…”

Section: Achnmentioning

confidence: 99%

Stereoselective Synthesis of the Urinary Metabolite N-Acetyl-S-(3,4-dihydroxybutyl)cysteine

Sharma

Laurens

Pilcher

2009

Synthetic Communications

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On exposure to the potential carcinogen 1,3-butadiene, the major urinary metabolite in humans is N-acetyl-S-(3,4-dihydroxybutyl)cysteine. A novel, stereoselective synthesis of this cysteine-butadiene metabolite has been developed that is suitable for the production of either diastereomer for use in occupational exposure analysis. L-cysteine and 4-bromo-1-butene are coupled via an S N 2 reaction to give the core structure. A Sharpless asymmetric dihydroxylation using the DHQD ligand provided the terminal 1,2-diol with the 3-hydroxyl group in the R configuration.Keywords: 1,3-butadiene, urinary metabolite, stereoselective synthesis, dihydroxylationThe volatile compound 1,3-butadiene used in the manufacture of rubber has been shown to cause cancer in mice and rats and has been labelled a probable carcinogen to humans. [1,2] Although environmental levels of this compound are low, workers in butadiene manufacturing plants and rubber factories can be exposed to high levels of this compound. [3] The metabolism of 1,3-butadiene in mice and rats has been the subject of many studies with the first step being an epoxidation with Cytochrome P450 dependent enzymes and then a variety of metabolites are produced depending on the activity of the epoxide hydrolases and the glutathione transferases. [4,5,6] The first metabolites to be identified were the cysteine derivatives MI and MII. [7] Subsequently the regio and stereoisomers of MII have been separated and identified [8] and the metabolites have been shown to arise predominantly from the R-butadiene monoxide. [4] The MII metabolites are the major urinary metabolite in rats and mice, but * Address correspondence to Lynne Pilcher, Department of Chemistry, University of Pretoria, Pretoria, 0002South Africa. Tel: +27 12 420-5384. E-mail: lynne.pilcher@up.ac.za cysteinethe MI metabolite proved to be the major metabolite in monkeys. [7] A more recent study of the metabolites from low level exposure (1-20 ppm) of rats and mice to 1,3-butadiene by inhalation,showed that MI and new metabolites MIII were the dominant urinary metabolites in these animals at concentrations encountered in occupational exposure situations. [6] A thorough investigation byAlbertini monitoring the urine of humans working in the production or the polymerisation of butadiene showed that MI is the major urinary metabolite in humans [3] and as such it represents a useful biomarker for monitoring the occupational exposure of factory workers to the potential carcinogen.[ To support the structural characterisation of the urinary metabolites, synthetic standards of the cysteine derivatives have been prepared. Sabourin first reported the synthesis of MI from acetyl cysteine and acetoxy methyl vinyl ketone as a mixture of diastereomers. [7] where the butadiene component was prepared from commercially available 2-butyne-1,4-diol.[10] The four MII metabolites were first cysteine -3 -prepared by Elfarra from acetyl cysteine and butadiene monoxide in a single reaction. The four regio/stereoisomers and a fifth ...

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Asymmetric Catalysis with Water: Efficient Kinetic Resolution of Terminal Epoxides by Means of Catalytic Hydrolysis

Cited by 1,311 publications

References 15 publications

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

Highly enantioselective epoxidation of styrenes: Implication of an electronic effect on the competition between spiro and planar transition states

Stereoselective Synthesis of the Urinary Metabolite N-Acetyl-S-(3,4-dihydroxybutyl)cysteine

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