Catalytic Enantioselective Epoxidation of Homoallylic Alcohols by Chiral Zirconium Complexes

Okachi, Takahiro; Murai, Norimoto; Onaka, Makoto

doi:10.1021/ol027261t

Cited by 65 publications

(26 citation statements)

References 15 publications

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“…For Zr 6 _ox, a Zr–O distance of 2.18 Å is also characteristic of Zr–peroxo groups 13p,14. However, as only one average Zr–O shell could be fitted, no further information about possible peroxo groups can be extracted from the EXAFS measurements.…”

Section: Resultsmentioning

confidence: 99%

Hydrolytic Stability and Hydrogen Peroxide Activation of Zirconium‐Based Oxoclusters

et al. 2014

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The hydrolytic stability of [Zr6(OH)4O4{O(O)CC(CH3)=CH2}12] (Zr6), and [Zr6O4(OH)4{O(O)CCH2CH=CH2}12]2·6[CH2=CHCH2C(O)OH] (Zr12) oxoclusters in different environments was thoroughly investigated by FTIR, Raman, and X-ray photoelectron spectroscopy (XPS). Specific information about the local structures around the Zr centers during the stability tests was achieved by in situ extended X-ray absorption fine structure (EXAFS) measurements, and the exact compositions were determined by inductively coupled plasma MS (ICP-MS) and elemental analysis. By this multidimensional spectroscopic approach, an overview on the structures formed after different treatments could be gained. The stability of the oxoclusters was then investigated in the presence of hydrogen peroxide, and the formation of peroxo–metal complexes was detected. Thus, a kinetic study was performed in acetonitrile to evaluate the performances of the oxoclusters as oxygen transfer catalysts. The oxidation of methyl p-tolyl sulfide to the corresponding sulfoxide and sulfone was chosen as a model reaction; in some cases, an interesting selectivity towards the formation of the sulfone was found over more than 4700 catalytic cycles

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Section: Resultsmentioning

confidence: 99%

Hydrolytic Stability and Hydrogen Peroxide Activation of Zirconium‐Based Oxoclusters

et al. 2014

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“…It is a double edged sword: the fundamental qualities that give organic materials their desirable mechanical properties cause many OTFTs to deviate from the ideal model. Covalently bonded molecules held together by weak van der Waals bonding often result in disordered microstructures, meaning OSCs have a lack of extended states, are littered with trapping sites, and support varying modes of transportation for charge carriers, whilst also being sensitive to measurement peculiarities arising from minority carrier trapping and injection . To add to the complexity, these intrinsic electrical attributes are highly dependent on how OSCs are designed and processed, and many of the intrinsic OSCs have characteristically wide bandgaps (2–4 eV), which can result in high Schottky barriers and large built‐in voltages at the interface between the source/drain (S/D) electrodes and the OSCs .…”

Section: Introductionmentioning

confidence: 99%

Recent Progress in High‐Mobility Organic Transistors: A Reality Check

et al. 2018

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Over the past three decades, significant research efforts have focused on improving the charge carrier mobility of organic thin-film transistors (OTFTs). In recent years, a commonly observed nonlinearity in OTFT current-voltage characteristics, known as the "kink" or "double slope," has led to widespread mobility overestimations, contaminating the relevant literature. Here, published data from the past 30 years is reviewed to uncover the extent of the field-effect mobility hype and identify the progress that has actually been achieved in the field of OTFTs. Present carrier-mobility-related challenges are identified, finding that reliable hole and electron mobility values of 20 and 10 cm V s , respectively, have yet to be achieved. Based on the analysis, the literature is then reviewed to summarize the concepts behind the success of high-performance p-type polymers, along with the latest understanding of the design criteria that will enable further mobility enhancement in n-type polymers and small molecules, and the reasons why high carrier mobility values have been consistently produced from small molecule/polymer blend semiconductors. Overall, this review brings together important information that aids reliable OTFT data analysis, while providing guidelines for the development of next-generation organic semiconductors.

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“… a Epoxidation procedures: entry a (ref ( 23 )), entry b (ref ( 24 )), entry c (ref ( 25 )), entry d (ref ( 26 )), entry e (ref ( 27 )), entry f (ref ( 28 )), entry g (ref ( 29 )), entry h (ref ( 30 )), entry i (ref ( 32 )), entry j (ref ( 33 )), entry k (ref ( 6a )), entry l (ref ( 9 )), entries m and n (ref ( 34 )). b Combined, isolated yield.…”

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confidence: 99%

Regio- and Enantioselective Catalytic Monoepoxidation of Conjugated Dienes: Synthesis of Chiral Allylic cis-Epoxides

Jat

Kumar

et al. 2015

Org. Lett.

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Ti(IV)-salan 4 catalyzes the diastereo- and enantioselective monoepoxidation of conjugated dienes using 30% H2O2 at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.

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Catalytic Enantioselective Epoxidation of Homoallylic Alcohols by Chiral Zirconium Complexes

Cited by 65 publications

References 15 publications

Hydrolytic Stability and Hydrogen Peroxide Activation of Zirconium‐Based Oxoclusters

Hydrolytic Stability and Hydrogen Peroxide Activation of Zirconium‐Based Oxoclusters

Recent Progress in High‐Mobility Organic Transistors: A Reality Check

Regio- and Enantioselective Catalytic Monoepoxidation of Conjugated Dienes: Synthesis of Chiral Allylic cis-Epoxides

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