No abstract
We report the observation of prompt J/psi via double cc; production from the e+e- continuum. In this process one cc; pair fragments into a J/psi meson while the remaining pair either produces a charmonium state or fragments into open charm. Both cases have been experimentally observed. We find cross sections of sigma[e+e- -->J/psieta(c)(gamma)]xB(eta(c)-->>or=4 charged)=(0.033(+0.007)(-0.006)+/-0.009) pb and sigma(e+e- -->J/psiD(*+)X)=(0.53(+0.19)(-0.15)+/-0.14) pb and infer sigma(e+e- -->J/psicc;)/sigma(e+e- -->J/psiX)=0.59(+0.15)(-0.13)+/-0.12. These results are obtained from a 46.2 fb(-1) data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB collider.
A practical asymmetric synthesis of a wide-spectrum agricultural fungicide, (S)-MA20565 (1), is described. The convergent synthesis was achieved starting from commercially available 3-(trifluoromethyl)aniline (7) in 44% overall yield through five steps and 2-bromobenzaldehyde (9) in 48% overall yield through four steps, respectively. (S)-O-[1-(3-Trifluoromethylphenyl)ethyl]hydroxylamine (2), a key intermediate of 1, was prepared via ruthenium(II)-catalyzed asymmetric transfer hydrogenation of 1-(3-trifluoromethylphenyl)ethanone (6) followed by chlorination using methanesulfonyl chloride and oxyamination using potassium acetohydroxamate with high level of stereocontrol.
From our interest in diheteracyclobutanes 1 bearing highly coordinate main group elements at the neighboring position, 1,2 we have reported the synthesis and thermolysis of the pentacoordinate 1,2λ 6 -oxathietane 2. 3,4 Almost quantitative oxirane formation from 2 has suggested a possibility that the oxathietane is an intermediate of the Corey-Chaykovsky reaction of oxosulfonium ylides with carbonyl compounds. 3It has been proposed that the Corey-Chaykovsky reaction 5 involves the formation of an anti-betaine followed by a back side attack of an oxido anion on the -carbon. 6 But, if the oxathietane is a real intermediate of the Corey-Chaykovsky reaction, 7 S-O bond heterolysis followed by C-C bond rotation is necessary for such an oxirane formation. Electrostatic interaction between the oxido anion and the sulfonium cation, which seems a driving force of the formation of the oxathietane ring, would resist the C-C bond rotation. In this case, an alternative mechanism such as a concerted mechanism or a front attack of the oxido anion without the C-C bond rotation can be expected to be operative. In order to elucidate these possibilities, we have decided to examine the stereochemistry of the oxirane formation. In this paper we wish to report the first example of the oxirane formation with retention of configuration and the theoretical study of this process.Two diastereomers of pentacoordinate 1,2λ 6 -oxathietanes 3a and 3b with the Martin ligand 8 were synthesized by the same method as previously reported (Scheme 1). 3 The separation of diastereomers 6a and 6b was nicely performed by flash column chromatography (FCC, SiO 2 ). The stereochemistry of 8a and 8b was determined by differential NOE experiments as follows: NOE between a methine proton of carbon-3 and orthoprotons of the phenyl group of carbon-4 was observed for (3S,4R)-or (3R,4S)-8a and not for (3S,4S)-or (3R,4R)-8b. Since the stereochemistry around a pentacoordinate sulfur and the relationship between the SdO group and the phenyl group at carbon-3 for 3 are considered to be the same as those reported for 2 and, furthermore, the relative stereochemistry around carbon-3 and carbon-4 is retained during the oxidation of 8, 3a and 3b are concluded to have the structures as shown in Scheme 1.Thermolysis of 3a gave the corresponding oxirane 9a along with 5, phenyl-migrated ketone 10, benzaldehyde (11), cyclic sulfinate 12, a diastereomeric mixture of cyclic thioacetal S-oxides 13, and cyclic thioacetal 14 (Scheme 2). 9 In sharp contrast to the thermolysis of 2, 3 the yield of oxirane 9a was † Gifu University.(1) Kawashima, T.; Okazaki, R. Synlett 1996, 600-608. For pentacoordinate 1,2-oxaphosphetanes, see: Kawashima, T.; Kato, K.; Okazaki, R. In the formation reaction of spiropentanes by the reaction of sulfonium cyclopropylides with carbonyl compounds, a mechanism involving an oxathietane was proposed as an alternative one involving a ring expansion to a σ-sulfurane having an oxirane ring followed by reductive elimination of the sulfide, see: Bogdanowicz, M. J...
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