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141.
Synthesis of a Pentacene‐Type Silaborin via Double Dehydrogenative Cyclization of 1,4‐Diboryl‐2,5‐disilylbenzene
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Tatsuya Hirofuji Dr. Toshiaki Ikeda Prof. Dr. Takeharu Haino Prof. Dr. Yohsuke Yamamoto Prof. Dr. Atsushi Kawachi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9734-9739
A new pentacene‐type silaborin, in which three benzene rings are bridged by silicon and boron atoms, has been synthesized and characterized by using NMR spectroscopy and X‐ray crystallographic analysis. The precursor, 1,4‐bis(dimesitylboryl)‐2,5‐bis(phenylsilyl)benzene ( 4 ), was prepared by stepwise introduction of a silyl group and a boryl group to a benzene ring starting from 1,4‐dibromobenzene. Double cyclization of 4 proceeds by a H‐Mes exchange and a B‐H/C‐H dehydrogenative condensation to afford pentacene‐type silaborin 5 . X‐ray crystal structure analysis reveals that 5 adopts a bent structure rather than a planar one. UV/Vis spectra and DFT calculations for 5 reveal a lowering of the LUMO energy level compared with corresponding anthracene‐type 3 . 相似文献
142.
143.
Umakoshi K Yamasaki T Fukuoka A Kawano H Ichikawa M Onishi M 《Inorganic chemistry》2002,41(16):4093-4095
Treatment of pyridine-2-thiol (pytH) with H(2) (60 atm) in the presence of 5-methylpyridine-2-thiolate (5-mpyt)-bridged dinuclear Pt(III), Pt(II), or Pd(II) complexes (1 mol %) in DMF at 150 degrees C for 72 h leads to the formation of pyridine in 3-51% yield. From the (1)H NMR study of the exchange reactions and of the products under D(2) pressure, it is suggested that the catalytic reaction involves bimetallic activation of the pyt ligand followed by the liberation of pyridine and H(2)S. 相似文献
144.
Kawada A Takeda S Yamashita K Abe H Harayama T 《Chemical & pharmaceutical bulletin》2002,50(8):1060-1065
The rare earth metal(III) trifluoromethanesulfonate (rare earth metal(III) triflate, RE(OTf)3) was found to be an efficient catalyst for aromatic nitration with carboxylic anhydride-inorganic nitrate as the nitrating agent. In the presence of a catalytic amount of RE(OTf)3, the nitration of substituted benzenes proceeded to afford the corresponding nitrobenzenes. Especially, scandium(III) trifluoromethanesulfonate (scandium(III) triflate, Sc(OTf)3) is the most active catalyst among our tested Lewis acids. It was also found that acetic anhydride-Al(NO3).9H2O is the most active nitrating agent in this system. 相似文献
145.
The orbital-phase theory was applied to propose pentagon stability in a well-defined manner. Cyclic delocalization of the lone pair electrons on the five-membered ring atoms through the vicinal sigma bonds was shown to be favored by the orbital-phase properties. The pentagon stability was found to be outstanding in saturated phosphorus five-membered rings in the puckered conformation, and was substantiated by the negative strain energy of cyclopentaphosphane, P(5)H(5) (3). The relative increments of the remarkable increase in the strain energies of protonation on the different atoms in the most stable conformers supported the significance of the cyclic delocalization of the lone pairs. Pentagon stability led to the design of three novel polycyclic phosphanes, P(12)H(4) (18), P(13)H(3) (19), and P(14)H(2) (20), with low strain energies due to many puckered pentagon units in them. The low stability of the dodecahedron P(20) (22) was suggested by the high strain energy due to its planar pentagon units. The pentagon stability is less significant in the saturated nitrogen ring molecules due to the greater energy gap between the n and sigma orbitals. 相似文献
146.
A polymer having a trithiocarbonate moiety in the main chain was applied as a polymeric precursor to the synthesis of a sequence ordered polymer by insertion polymerization of styrene into the main chain by a RAFT mechanism. 相似文献
147.
Ayabe M Ikeda A Shinkai S Sakamoto S Yamaguchi K 《Chemical communications (Cambridge, England)》2002,(10):1032-1033
Porphyrin dimer 1, which does not have an inside cavity and cannot interact with [60]fullerene (C60), becomes an excellent C60-acceptor with a large cavity in the presence of a Pd(II) complex. 相似文献
148.
[reaction: see text] Radical cascade reaction with various 1,4-dienes and 1,4-enynes using dimethyl 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor smoothly proceeds through an iodine atom transfer mechanism to give functionalized bicyclo[3.3.0]octane derivatives in good yields. 相似文献
149.
Atsushi Moriwaki 《Compositio Mathematica》2002,132(2):191-228
Let M
g
be the moduli space of smooth curves of genus g 3, and M¯
g
the Deligne-Mumford compactification in terms of stable curves. Let M¯
g
[1] be an open set of M¯
g
consisting of stable curves of genus g with one node at most. In this paper, we determine the necessary and sufficient condition to guarantee that a
-divisor D on M¯
g
is nef over M¯
g
[1], that is, (D · C) 0 for all irreducible curves C on M¯
g
with C M¯
g
[1] . 相似文献
150.
The transgalactosylation rate catalyzed by the lipid-coated beta-d-galactosidase in supercritical fluoroform (scCHF3) can be reversibly controlled by changing temperature or pressure (reflecting polarity changes) without damaging enzymes. 相似文献