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71.
M. Nakagawa S. Kato H. Fukazawa Y. Hasegawa J. Miyazawa T. Hino 《Tetrahedron letters》1985,26(48):5871-5874
Oxytryptophans 3, which are readily obtained by dye-sensitized photooxygenation of tryptophan followed by acid treatment, undergo a facile N,N′-transacylation to give the 3-(2-aminophenyl)-2-pyrrolidones 4 in the absence of oxygen, whereas in the presence of oxygen 3a was oxidized to kynurenine. 相似文献
72.
Shoji M Imai H Shiina I Kakeya H Osada H Hayashi Y 《The Journal of organic chemistry》2004,69(5):1548-1556
An oxidative dimerization reaction, involving the three successive steps of oxidation, 6 pi-electrocyclization, and Diels-Alder reaction, has been experimentally and theoretically investigated for the three 2-alkenyl-3-hydroxymethyl-2-cyclohexen-1-one derivatives epoxyquinol 3, epoxyquinone 6, and cyclohexenone 10. Of the sixteen possible modes of the oxidation/6 pi-electrocylization/Diels-Alder reaction cascade for the epoxyquinone 6, and eight for the cyclohexenone 10, only the endo-anti(epoxide)-anti(Me)-hetero and endo-anti(Me)-hetero modes are, respectively, observed, while both endo-anti(epoxide)-anti(Me)-hetero and exo-anti(epoxide)-anti(Me)-homo reaction modes occur with the epoxyquinol 3. Intermolecular hydrogen-bonding is found to be the key cause of formation of both epoxyquinols A and B with 3, although epoxyquinone 6 and cyclohexenone 10 both gave selectively only the epoxyquinol A-type product. In the dimerization of epoxyquinol 3, two monomer 2H-pyrans 5 interact with each other to afford intermediate complex 28 or 29 stabilized by hydrogen-bonding, from which Diels-Alder reaction proceeds. Theoretical calculations have also revealed the differences in the reaction profiles of epoxyquinone 6 and cyclohexenone 10. Namely, the rate-determining step of the former is the Diels-Alder reaction, while that of the latter is the 6 pi-electrocyclization. 相似文献
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74.
Hiroki Nakamura Jiro Tanaka Nobuaki Nakashima Keitaro Yoshihara 《Chemical physics letters》1981,77(2):419-421
The photoionization of 8-anilino-1-naphthalenesulfonate in polar solvents occurs through a biphotonic process, as proved by nanosecond flash photolysis. A transient absorption of a charge transfer to solvent (CTTS) state is found with ≈10 ns life-time. The state is shown to be an intermediate of the photoionization process. 相似文献
75.
Fullerenols revisited as stable radical anions 总被引:2,自引:0,他引:2
Husebo LO Sitharaman B Furukawa K Kato T Wilson LJ 《Journal of the American Chemical Society》2004,126(38):12055-12064
The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene. 相似文献
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