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A new bulky bromobenzene of the metacyclophane type was converted to an unsymmetrically substituted 1,4-diphos-phabutatriene whose spin-spin coupling constant (3Jpp) turned out to be larger, for the first time, than the 2Jpp value of the corresponding 1,3-diphosphaallene. 相似文献
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Shigekazu Ito Manabu Kikuchi Joji Miura Noboru Morita Masaaki Yoshifuji 《Journal of Physical Organic Chemistry》2012,25(9):733-737
Air‐tolerant 2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl singlet biradicals can be prepared by utilizing the unique reactivity of a kinetically stabilized P≡C triple bond compound. In this procedure, we studied the spectroscopic properties of a fundamental unsymmetrical P‐heterocyclic biradical containing both PEt and PMe moieties, and the effects of the PCH2OMe group in relation to the stability of the P‐heterocyclic biradical skeleton. The experimentally observed nuclear magnetic resonance and photo‐absorption parameters of 1‐ethyl‐3‐methyl‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl were discussed based on our previous findings and density functional theory calculations, suggesting particular structural characteristics of the P‐heterocyclic biradical skeleton and aromatic substituent effects on the sp2‐C atoms in the 4‐membered ring. Introduction of the methoxymethyl group in the P2C2 biradical moiety gave more stabilized 1,3‐diphosphacyclobutane‐2,4‐diyl derivatives. In comparison with considerably unstable biradicals bearing propargyl substituents, relatively higher lowest unoccupied molecular orbital energies suggest reluctant oxidation of the P‐heterocyclic skeleton. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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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
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Masaaki Yoshifuji Kozo Toyota Naoki Inamoto Ken Hirotsu Taiichi Higuchi 《Tetrahedron letters》1985,26(52):6443-6446
The sterically protected -phosphaethylene, -2-phenyl-1-(2,4,6-tri-t-butylphenyl)phosphaethylene (1-Z), was analyzed by X-ray crystallography. 相似文献
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Phosphaethynes bearing a 2,6-di-tert-butyl-4-(dimethylamino)phenyl, 2,6-di-tert-butyl-4-methoxyphenyl, or 2,6-di-tert-butylphenyl group were prepared. A (31)P NMR spectroscopic investigation of the chemical shifts indicated that electron-donating groups at the para position cause shifts to a higher field. Bathochromic shifts caused by the electron-donating groups were apparently observed in UV-vis spectra. The structure of 2-[2,6-di-tert-butyl-4-(dimethylamino)phenyl]-1-phosphaethyne was analyzed by X-ray crystallography. 相似文献
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The first total synthesis of ankorine (4), an Alangium lamarckii alkaloid, has been accomplished in the form of a recemic modification by means of an initial condensation of 2-benzyloxy-3,4-dimethoxyphenacyl bromide with the lactim ether 6, derived from ethyl (±)-trans-5-ethyl-2-oxo-4-piperidineacetate (5), and succeeding steps proceeding through the intemediates 7a, 8a, 9a, 10a (X=Cl), 11a, and 12a. A parallel synthetic route starting with 3,4,5-trimethoxyphenacyl bromide and 6 gave (±)-11-methoxyprotoemetinol (12c) via the intermediates 7c, 8c, 9c, 10c (X =I,ClO4), and 11c. The trimethyl ether 12c did not match the O-Me derivative (type 12e) of natural ankorine. Thus, the formula 4 defines the structure and relative stereochemistry of ankorine. 相似文献
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