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111.
A simple one-pot and efficient method is described for the synthesis of pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidinone derivatives 6 via a tandem aza-Wittig/heterocumulene-mediated annulation process. The iminophosphorane 3 reacted with aryl isocyanates, followed by heterocyclization on addition of secondary amines to give the corresponding guanidine intermediates 5, which were cyclized in the presence of a catalytic amount of potassium carbonate to tricyclic compounds 6. Similarly, iminophosphorane 3 reacts with phenols, thiophenol, or ROH to give 2-aryl(alkyl)oxy(thio)pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidinone derivatives 7 in good yields. The corresponding carbodiimide 4c and guanidine-type intermediate compounds 5 could be isolated and characterized, thus confirming the suggested reaction pathway. However, two isomeric pyrazinothienopyrimidinones 8 and 9 may be produced in the reaction of iminophosphorane 3 with aromatic isocyanates and subsequent reaction with primary amines in the presence of a catalytic amount of potassium carbonate. The effects of the nucleophiles and isocyanates on the regioselectivity of the cyclization have been investigated. 相似文献
112.
113.
Yasumasa Hirashima 《Topology and its Applications》2007,154(12):2412-2424
Pairings and copairings of topological spaces induce pairings of function spaces. These induced pairings of function spaces are studied. For this purpose, the C-open topology of function spaces is studied for subcategories C of Top. It is shown that the C-open topology enjoys good properties for homotopy theory. Making use of the C-open topology, theory of induced pairings is established and fundamental results on pairings which deduce various commutativity properties of elements in homotopy set are extended to function spaces. 相似文献
114.
An optical output power exceeding 210 mW has been achieved using 1.625-μm strained multiple quantum well lasers at a forward
current of 800 mA under pulsed operation. We introduced tensile-strained barrier layers to increase internal quantum efficiency.
High quantum efficiency is attributed to improved of hole injection efficiency and suppressed electron overflow from wells.
The 1.625-μm high-power lasers are expected to be applied to optical time-domain reflectometers, which enable regular communication
light to be used. 相似文献
115.
Deep hydrodesulfurization (HDS) of sterically hindered sulfur compounds in gas oils will require enhanced hydrogenation activity to hydrogenate the aromatic rings of the sulfur compounds. Although H2S is known to inhibit the direct HDS route for most of the sulfided catalysts, its promotion to the hydrogenation and subsequent HDS was newly observed for unsupported MoS2. This promotion suggests that ultra deep HDS over sulfide catalysts can be achieved along with high metal loading, minimal support-metal interactions and optimal dependence on the Ni species. On the other hand, the strong hydrogenation activity of sulfur-tolerant noble metal catalysts suggests that ultra deep HDS as well as deep aromatics saturation can be achieved. This paper discusses recent catalytic approaches for ultra deep HDS using conventional sulfide catalysts and/or noble metal catalysts, such as the newly developed Pd-Pt/Yb-USY zeolite catalyst. 相似文献
116.
Kaoru Nakamura Yasumasa Shizume Takashi Sugiyama Atsuyoshi Ohno Shizaburo Oka 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):153-155
Abstract Electrochemical isomerization of 1-phenyl-2, 2-dimethylpropane-1-thione S-oxide (phenyl-t-butylsulfine, E and Z form, 1a and 1b) was studied. Anodic isomerization of 1a gave the two isomers of the sulfine only, but cathodic reductive isomerization of 1a gave pivalophenone and 1-cyano-2-phenyl-3, 3-dimethyl-1-butene in addition to the E and Z isomers. This is the first example of an electrochemical reaction of a sulfine. 相似文献
117.
118.
Detection of small RNA molecules by a combination of branched rolling circle amplification and bioluminescent pyrophosphate assay 总被引:1,自引:0,他引:1
Polyfluorinated compounds (PFCs) are a relatively new and diverse set of compounds analyzed as contaminants in food. Their
unique physical-chemical properties dictate the methods used for their analysis. Current analyses of the more volatile PFCs
involve gas chromatography–mass spectrometry; liquid chromatography–tandem mass spectrometry is generally used for the less
volatile PFCs. Considerations in the analysis of PFCs in foods include contamination from the widespread presence of materials
that contain various PFCs, endogenous interfering compounds, and matrix effects. Future opportunities for research on PFCs
in food exist, particularly in the areas of biological molecule–PFC interactions and the effects of food processing on these
interactions. Future research will be facilitated by the synthesis of a wider variety of analytical standards. 相似文献
119.
A novel sensing method for polyhydroxy compounds has been established based on the stimuli-responsive inclusion complex of boronic acid-modified amylose with iodine. An aqueous solution containing the boronic acid-modified amylose and iodine was coloured bluish purple due to encapsulation of iodine within the helical cavity of amylose. When polyhydroxy compounds were added, the solution gradually lost its colour with increasing concentration of polyhydroxy compounds. This colour change was attributed to the dissociation of iodine from the amylose cavity in response to the polyhydroxy compounds. According to detailed examinations, it was concluded that the origin of the responsiveness is derived from an electrostatic repulsion between anionic boronate groups and iodine. 相似文献
120.
Yasumasa Hirashima 《Topology and its Applications》2011,158(3):445-456
Topologies on base point preserving function spaces are studied making use of the Brown-Booth-Tillotson C-smash product and the topologies on function spaces defined by the classes C of exponentiable spaces. Some conditions on the classes C are obtained for exponential bijections and exponential homeomorphisms in the category of topological spaces with base point. Conditions for exponential homeomorphisms are obtained for CW-complexes whose cellular structure implies precise results. 相似文献