Bis-silicon-bridged stilbene homologues synthesized by new intramolecular reductive double cyclization

A homologous series of bis-silicon-bridged stilbenes has been synthesized on the basis of a new intramolecular reductive cyclization of bis(o-silyl)-diphenylacetylene. Thus, the reaction of bis(o-silyl)-diphenylacetylenes with excess lithium naphthalenide undergoes the two-electron reduction at the acetylene moiety to produce a dianion intermediate, which further undergoes a double cyclization in a 5-exo mode to produce the bis-silicon-bridged stilbenes. This methodology can also be applied to the synthesis of tetrakis-silicon-bridged bis(styryl)benzenes. The silicon-bridged pi-conjugated systems thus prepared show intense fluorescence in the visible region. Comparison of a bis-silicon-bridged stilbene with its carbon analogue demonstrates the substantial effects of the silicon-bridges on the electronic structures and thus on the fluorescence properties.     

Oxidation of siliconsilicon and siliconhydrogen bonds with molecular oxygen and bis(trimethylsilyl) peroxide

The siliconsilicon bond which is either strained or substituted with more than two fluorine atoms is easily oxidized with molecular oxygen and bis-(trimethylsilyl) peroxide (BSPO) at or below room temperature to form mainly the corresponding disiloxane. The former aerobic oxidation is inhibited by 2,4,6-tri(t-butyl)phenol, while the latter is not. Oxidation of the SiH bond with BSPO and the preparation of three new (fluoro)methyldisilanes are also described.     

Free oscillator realization of Laguerre polynomials

Theoretical and Mathematical Physics - We revisit the radial oscillator from the standpoint of a free oscillator realization. By using a free oscillator, namely, the creation/annihilation operators...     

Asymmetric synthesis via chiral silicon reagents. Chiral α-hydroxyalkyl anion equivalents from vinylsilanes containing optically active amino or alkoxy groups on silicon

Chiral vinylsilanes containing optically active functional groups on silicon have been used as precursors for chiral α-hydroxyalkyl anion equivalents via a sequence of addition of η-butyllithium, coupling with organic halides, and oxidative cleavage of the silicon-carbon bond, to give optically active alcohols of up to 60% ee.     

Vertebrate collagenase inhibitor. I. Tripeptidyl hydroxamic acids

A series of tripeptidyl analogues carrying hydroxamic acid residue at the C-terminus of the molecule were synthesized, and their inhibitory activities against vertebrate collagenase and other metalloenzymes including bacterial collagenase were examined. Both Z-Pro-Leu-Ala-NHOH and Z-Pro-D-Leu-D-Ala-NHOH showed highly specific and potent inhibitory activity against tadpole and human skin collagenases with an IC50 of 10(-6) M order.     

Boron trifluoride induced palladium-catalyzed cross-coupling reaction of 1-aryltriazenes with areneboronic acids

[reaction: see text] Aryltriazenes are directly coupled with areneboronic acids in the presence of a catalytic amount of Pd(2)(dba)(3) and P(tBu)(3) together with 1 equiv of BF(3).OEt(2) in DME to afford the corresponding biaryl products in up to 98% yield. A carbonylative cross-coupling reaction under a carbon monoxide atmosphere is also found to give the corresponding diaryl ketone with a similar catalyst system.     

Adsorption and emission enhancement behavior of 4,4′-bipyridine on dispersed montmorillonite nano-sheets under aqueous conditions

The adsorption and photochemical behavior of 4,4′-bipyridine (BPy) on an exfoliated single montmorillonite nano-sheet (MtNS) was investigated in water. Under the appropriate conditions, BPy was adsorbed on the MtNS as a monomer state. BPy exhibited a relatively large red shift by 30?nm in the absorption spectrum, and showed significant emission enhancement in the fluorescence spectrum, contrary to the non-fluorescent property of BPy in water without MtNS. From the investigation using protonated BPy (BPyH₂²⁺) under acidic conditions, it was turned out that BPy was adsorbed as BPyH₂²⁺ on MtNS even under neutral conditions. From the analysis based on the Langmuir adsorption isotherm, the saturated adsorption amount of BPy on MtNS was calculated to be 3.2?×?10^?2 molecule nm^?2.     

An efficient route to heteroarene-substituted vinyl- and allyl-silanes via palladium-phosphine complex catalyzed cross-coupling

Heteroarene-substituted vinyl- and allyl-silanes were obtained in good yields by the cross-coupling reaction of either heteroaryl Grignard reagents with halovinyl- and haloallyl-silanes or, alternatively, silyl- and silylmethyl-substituted vinylmetallic reagents with heteroaryl halides in the presence of PdCl₂(dppb) as a catalyst.