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1.
Dihydrothiinone 9a undergoes photocycloaddition regioselectively to all three C?C bonds of penta‐1,2,4‐triene ( 10 ), the relative stabilities of the biradical intermediates determining the product distribution. In contrast, cyclohexenone 9b and dihydropyranone 9c afford more complex mixtures of bicyclo[4.2.0]octanones, which also turn out to be less stable on chromatographic workup, reflecting the higher strain due to the shorter bond lengths (C? O and C? C vs. C? S) in the six‐membered rings, respectively. 相似文献
2.
Masaaki Yoshifuji Yuichi Hirano Gregor Schnakenburg Rainer Streubel Edgar Niecke Shigekazu Ito 《Helvetica chimica acta》2012,95(10):1723-1729
1,3‐Di(tert‐butyl)‐2,4‐bis[2,4,6‐tri(tert‐butyl)phenyl]‐1,3‐diphosphacyclobutane‐2,4‐diyl was formed from [2,4,6‐tri(tert‐butyl)phenyl]phosphaacetylene and t‐BuLi. In addition, the X‐ray diffraction analysis was carried out, together with theoretical calculations of the structure and NMR data. 相似文献
3.
Shigekazu Ito 《Tetrahedron letters》2018,59(1):1-13
This minireview summarizes recent findings on isolable congeners of cyclobutane-1,3-diyl from the views of structural characters, usefulness for organo electronics, and activation of small molecules. Recent findings on isolable cyclopentane-1,3-diyl, 2,4-dimethylene-1,3-cyclobutanediyl, and cyclobutadiene are also overviewed. This article focuses on the reports on the isolable biradicals that have been published since 2013. 相似文献
4.
《Tetrahedron letters》2004,45(24):4711-4714
Thermal and thionyl chloride induced cycloaromatizations of secondary and tertiary aryldiacetylene alcohols were studied. The secondary alcohol did not respond to thionyl chloride, but in all the other cases presumptive biradical intermediates evolved either by intramolecular radical coupling or, when derived from a xanthene scaffold, by intramolecular radical acylation to a diketone that finally afforded a p-methylene-quinone. 相似文献
5.
Shigekazu Ito Manabu Kikuchi Masaaki Yoshifuji 《Journal of organometallic chemistry》2007,692(13):2761-2767
A kinetically stabilized phosphaalkyne bearing a bulky Mes∗ (2,4,6-tri-t-butylphenyl) group is useful compound to prepare an enormous number of highly stable 1,3-diphosphacyclobutane-2,4-diyls through reactions with a lithium reagent and an electrophile. By utilizing this synthetic protocol, we prepared several non-symmetrical 1,3-diphosphacyclobutane-2,4-diyls in which the substituents on the phosphorus are different. Furthermore, we succeeded in preparation and characterization of novel air-tolerant symmetrical 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyls bearing the identical alkyl substituents on the phosphorus atoms. Structures and properties of the 1,3-diphosphacyclobutane-2,4-diyls indicate characters as singlet ground-state carbon centered biradicals. In addition to those biradicals, we succeeded in preparation and isolation of a novel P-heterocyclic air-stable neutral radical as well as a P-heterocyclic cation radical. 相似文献
6.
Armando Navarro-Vázquez José-Lorenzo Alonso-Gómez Johan Lugtenburg María-Magdalena Cid 《Tetrahedron》2010,66(21):3855-3860
Thermal Diels-Alder reaction of vinyl ketenimines with 13C-labeled 2-butynoate, efficiently prepared from 13C4-acetoacetate via the enol triflate, rendered at 160 °C the corresponding methylanthranilic ester isotopomerically pure. However, when the reaction was run at 100 °C, 7% of isotope exchange between C6a and C5 was observed. This result is explained through a base-like catalyzed isomerization of the alkyne to the corresponding allene. Combined DFT and coupled-cluster computations show the feasibility of this mechanistic proposal. Better agreement between DFT and coupled-cluster activation and reaction energies is observed for the meta-GGA MPWB1K functional as compared to previous B3LYP results. 相似文献
7.
ABSTRACTFor the first time, a 1H solid-state photo-CIDNP effect is reported. The effect is observed in frozen solution of cyclohexanone in 1,4-dioxane-d8 under magic-angle spinning and continuous irradiation by the full spectrum of a xenon arc lamp. The spectral features show close similarity with those observed by 1H liquid-state photo-CIDNP NMR. 相似文献
8.
Four biradicals of differing chain lengths have been prepared by spin-labelling the sulphhydryl groups of dithiothreitol.
Temperature-dependent EPR spectra of these biradicals indicate that the dynamics of biradicals is associated with both fast
and slow exchanges of conformations. The three-conformational model incorporating cage configuration is found to be more appropriate.
Certain thermodynamic parameters of conformationalchanges have been calculated from the experimental EPR parameters, obtained
by the use of simulation procedures developed recently. 相似文献
9.
《Chemical record (New York, N.Y.)》2018,18(4):445-458
Installing π‐functional substituents on the skeletal phosphorus atoms of the air‐tolerant 1,3‐diphosphacyclobutane‐2,4‐diyl unit are promising for tuning the open‐shell singlet P‐heterocyclic chromophore. The sterically encumbered 1,3‐diphosphaCycloButen‐4‐yl Anion ( CBA ), generated from the phosphorus‐carbon triple bond, was available for the regioselective arylation via nucleophilic aromatic substitution (SNAr) reaction, addition to arynes, and single‐electron transfer (SET) process affording the corresponding P‐arylated 1,3‐diphosphacyclobutane‐2,4‐diyls. The photo‐absorption and redox properties correlated with the effects of the aryl substituents on the 1,3‐diphosphacyclobutane‐2,4‐diyl unit. The X‐ray analyses enabled not only to discuss the metric parameters but also to visualize the radicalic electrons via the electron‐density distribution analysis. The electron‐donating character of the P‐heterocyclic chromophores induced the p‐type semiconductor behavior. Detection of hydrogen fluoride via formation of the 1λ5,3λ5‐diphosphete derivative was also developed. 相似文献
10.
Manabu Abe 《中国化学会会志》2008,55(3):479-486
Recently, the demand for synthetic oxetanes has increased because the highly strained structure allows specific biologic functions in vivo and also serves unique purposes in industrial materials. This review article summarizes recent progress in regio‐, site‐, and stereo‐selective formation of oxetanes via a photochemical process. 相似文献