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21.
Dieter Seebach Thomas Weller Gerd Protschuk Albert K. Beck Marvin S. Hoekstra 《Helvetica chimica acta》1981,64(3):716-735
Preparation of 1,3-Diketones and of Nitro-diketones by (1:1)-Acylation of Lithium Enolates with Acyl Chlorides Slow addition of precooled solutions of lithium enolates in THF (Fig. 1) to solutions of equimolar amounts of acyl chlorides in the same solvent at temperatures between ? 80 and ? 100° furnishes 1, 3-diketones in acceptable to good yields (Tables 1?3). Even 3-nitropropionyl and 4-nitrobutyryl chloride can be employed for the (1:1)-acylation of enolates to give the synthetically useful 5- and 6-nitro-1, 3-diketones 13 and 25 , respectively. The scope and the limitations of this method of preparing 1, 3-diketones are given and are compared with alternative methods. 相似文献
22.
Battaglia TM Dunn EE Lilley MD Holloway J Dable BK Marquardt BJ Booksh KS 《The Analyst》2004,129(7):602-606
The development of a field portable fiber optic Raman system modified from commercially available components that can operate remotely on battery power and withstand the corrosive environment of the hydrothermal vents is discussed. The Raman system is designed for continuous monitoring in the deep-sea environment. A 785 nm diode laser was used in conjunction with a sapphire ball fiber optic Raman probe, single board computer, and a CCD detector. Using the system at ambient conditions the detection limits of SO(4)(2-), CO(3)(2-) and NO(3)(-) were determined to be approximately 0.11, 0.36 and 0.12 g l(-1) respectively. Mimicking the cold conditions of the sea floor by placing the equipment in a refrigerator yielded slightly worse detection limits of approximately 0.16 g l(-1) for SO(4)(-2) and 0.20 g l(-1) for NO(3)(-). Addition of minerals commonly found in vent fluid plumes also decreased the detection limits to approximately 0.33 and 0.34 g l(-1) respectively for SO(4)(-2) and NO(3)(-). 相似文献
23.
Off-lattice Monte Carlo simulations employing the PIVOT algorithm are used to generate ideal and excluded volume linear polymers in two dimensions. The form factor at small and large wave vectors is calculated from the resulting configurations and compared to the exact equation for ideal chains and to both scaling and renormalization group predictions for excluded volume chains. It is found that using the des Cloizeaux form for the distance distribution function in an analytic calculation of the form factor leads to close agreement with the Monte Carlo data and that simple expressions for both the small and large wave vector expansions reproduce the essential features of the form factor. 相似文献
24.
Hirotaka Kudo Marvin L. Tedjamulia Raymond N. Castle Milton L. Lee 《Journal of heterocyclic chemistry》1984,21(1):185-192
We describe the synthesis of thieno[2,3-c]dibenzothiophene ( 6 ), thieno[3,2-c]dibenzothiophene ( 10 ), thieno-[3,2-a]dibenzothiophene ( 14 ), thieno[2,3-a]dibenzothiophene ( 16 ), benzo[1,2-b:4,3-b]bisbenzo[b]thiophene ( 18 ), benzo[1,2--6:3,4-b]bisbenzo[b]thiophene ( 20 ), benzo[2,1--6:3,4-b]bisbenzo[b]thiophene ( 22 ), benzo[1,2-b:3,4-g]bisbenzo[b]thiophene ( 27 ), benzo[1,2-b:4,3-e]bisbenzo[b]thiophene ( 29 ), benzo[2,1--6:3,4-g]bisbenzo[b]thiophene ( 36 ), benzo[2,1--6:4,3-e]bisbenzo[b]thiophene ( 38 ), benzo[1,2--6:4,3-g]bisbenzo[b]thiophene ( 41 ), benzo[1,2-b:4,5-g]bisbenzo[b]thiophene ( 42 ), benzo[1,2-b:3,4-e]bisbenzo[b]thiophene ( 44 ) and benzo-[1,2-b:5,4-e]bisbenzo[b]thiophene ( 45 ). 相似文献
25.
Marvin L. Tedjamulia Hirotaka Kudo Raymond N. Castle Milton L. Lee 《Journal of heterocyclic chemistry》1984,21(2):321-325
The syntheses of naphtho[1,2–6:7,6-b′]bisbenzo[b]thiophene ( 4 ), naphtho[1,2–6:7,8-b′]bisbenzo[b]thiophene ( 5 ), naphtho[2,1-b:7,6-b′]bisbenzo[b]thiophene ( 8 ), naphtho[2,1-b:7,8-b′]bisbenzo[b]thiophene ( 9 ), naphtho-[1,2–6:5,6-b′]bisbenzo[b]thiophene ( 14 ), naphtho[1,2–6:6,5-b]bisbenzo[b]thiophene ( 17 ) and naphtho[2,1–6:-6,5-b′]bisbenzo[b]thiophene ( 23 ) are reported. 相似文献
26.
Cory Momany Marvin L. Hackert Jyotsna Sharma Narinder S. Poonia 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):343-354
Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]2DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal2DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]2DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)2DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)2DB24C8 and (NaSal)2DB24C8 molecules. The crystals are monoclinic,P21/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, Å3,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na2- and K2-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K2-crown being nearly planar and the Na2-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na2-molecule; 82.7° K2-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K+K+ and Na+Na+ distances in the respective molecules are 3.95 and 3.34 Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages). 相似文献
27.
The synthesis of the eight-membered ring containing two disulfides, 1,2,5,6-tetrathiacyclooctane, is described. It is characterized by x-ray crystallography as well as by mass, IR, Raman, 1H-NMR und UV spectroscopy 相似文献
28.
Kenneth Gonsalves Lin Zhan-Ru Robert W. Lenz Marvin D. Rausch 《Journal of polymer science. Part A, Polymer chemistry》1985,23(6):1707-1722
Three types of isopropenylmetallocene monomers were synthesized and subjected to polymerization and copolymerization by cationic initiators; (1) isopropenylferrocene (IF); (2) (η5-isopropenylcyclopentadienyl)dicarbonylnitrosylmolybdenum (IDM); and (3) 1,1′-diisopropenylcyclopentadienylstannocene (DIS), and related derivatives of each. IF was synthesized by a three-step procedure involving the acetylation of ferrocene, conversion of the latter to 2-ferrocenyl-2-propanol, and dehydration of the carbinol. IF was homopolymerized under various cationic initiation conditions, but only low molecular weight homopolymers were obtained. Copolymerization of IF with styrene and with p-methoxy-α-methylstyrene also gave only low molecular weight products. The formation of only low molecular weight polymers in all polymerization reactions is believed to result from the effect of the unusually high stability of ferrocenyl carbenium ions on its propagation reaction. The observed polymerization behavior of α-trifluoromethylvinylferrocene is in accord with this conclusion. IDM and DIS did not form polymeric products under cationic conditions, although copolymers could be obtained for each of these monomers and styrene with a free radical polymerization initiator (AIBN). 相似文献
29.
30.
SGTx1 is a new neurotoxin from the venom of Scodra griseipes. Because of the small quantity of this natural peptide available, mass spectrometry was used to obtain information on its higher-order structure. The kinetics of reduction by 1,4-dithiothreitol (DTT) was monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), and showed that one of the three disulfide bridges was appreciably more accessible to the DTT. Studies based on the charge state distribution (CSD) and H/D exchange of the non-reduced peptide, under neutral and acidic conditions, were performed using electrospray mass spectrometry (ES-MS). In neutral solution, SGTx1 showed a maximum charge state of four compared with seven potentially protonated basic residues, and all labile hydrogens were exchanged. However, under acidic conditions, a maximum charge state of only five was observed, and four of the labile hydrogens could not be deuterated. These observations are interpreted in terms of a rigid structure maintained by the disulfide bridges, which can be temporarily relaxed by disulfide bridge scrambling only at higher pH values. 相似文献