Numerous gas/solid reactions of nitrogen dioxide with organic substrates are investigated preparatively and mechanistically. Gaseous NO2 reacts with crystalline stable free radicals (nitroxyls 1, verdazyl 6) by electron transfer. The nitrite ions formed are irreversibly oxidized by NO2 via oxygen atom transfer. Solid cation nitrates are formed quantitatively. Thione bonds of thiohydantoins 8 are transformed to carbonyl bonds with formation of sulfur and NO presumably via nitrites as intermediates. Hydantoin 13 oxygenates at its free 5-methylene group via C-H abstraction and nitrite or it undergoes N-1 nitration via N-H abstraction depending on the conditions. Both reactions proceed quantitatively. 1,3-Oxazolidin-2-one (15) gives N-nitration and N-nitrosation with the NO produced. Nonenolized crystalline barbituric acids 17 are quantitatively nitrated (C-N bond formation with radicals) at their methylene groups. 4-Hydroxybenzaldehyde (19) and vanilline (22) give quantitative aromatic nitration (C-N bond formation with arenes) without melting. All possible regioisomers are formed. Solid 9-methylanthracene (26) gives a quantitative yield of its 10-nitro derivative 27. Crystalline anthracene (28) and gaseous NO2 yield 3 primary products 29 (cis; trans) and the new dimeric product 30 as well as the stable secondary products 31 and 32. The gas/solid tetranitration of tetraphenylethylene (33) is severely hindered by the water of reaction. However, a 95% yield of pure tetrakis(p-nitrophenyl)ethylene is obtained if the drying agent MgSO4 . 2H(2)O is admired and the product 34 extracted. The gas/solid procedures avoid solvents and fuming nitric acid. They give pure products without necessity for recrystallization in most cases and they avoid wastes. Atomic force microscopy (AFM) measurements on prominent faces of single crystals of 1a, 11a, 28, and 33 reveal phase rebuildings with well-directed long-range molecular transports. Nanoliquids were only present on (110) of 28. The characteristic AFM features are correlated with known X-ray crystal structure data and compared with previous results. The shape of the features depends on the molecular packing in the crystal bulk and on the molecular shapes. Molecular interpretations of the AFM features are given.
Enantioselective synthesis of (S)-calycotomine employing catalytic asymmetric hydrogenation with an iridium(I)–(R)-BINAP–phthalimide complex
摘要:
An optically active l-hydroxymethyl-substituted tetrahydroisoquinoline alkaloid, (S)-calycotomine 1, was conveniently synthesized by using catalytic asymmetric hydrogenation of 1-benzyloxymethyl-3,4-dihydro-6,7-dimethoxyisoquinoline 6 with 0.5 mol % of an iridium(I) complex of (R)-BINAP in the presence of 3,4,5,6-tetrafluorophthalimide. (C) 1998 Elsevier Science Ltd. All rights reserved.
Enantiospecific Assembly of a Homochiral, Hexanuclear Palladium Complex
作者:Howard M. Colquhoun、C. Timothy Powell、Zhixue Zhu、Christine J. Cardin、Yu Gan、Paula Tootell、Josephine S. W. Tsang、Neil M. Boag
DOI:10.1002/ejic.200801045
日期:2009.3
The resulting tris-parabanato(2-)-bridged, hexapalladium complex is thus homochiral (R,R,R,R,R,R or S,S,S,S,S,S), as demonstrated by H-1 NMR spectroscopy and by X-ray analysis of a racemic crystal which shows the complex to possess a tapering, twisted, trigonal-prismatic skeleton of palladium atoms with threefold crystallographic symmetry. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany
作者:Reinhard Sarges、Rodney C. Schnur、John L. Belletire、Michael J. Peterson
DOI:10.1021/jm00396a037
日期:1988.1
formation from glucose, catalyzed by the enzyme aldosereductase, is believed to play a role in the development of certain chronic complications of diabetes mellitus. Spiro hydantoins derived from five- and six-membered ketones fused to an aromatic ring or ring system inhibitaldosereductase isolated from calf lens. In vivo these compounds are potent inhibitors of sorbitol formation in sciatic nerves of
acid required a melt reaction providing a 78% yield of 3-oxodihydroquinoxalinyl-2-urea 22 and side products. Despite numerous reaction steps, most of these uncatalyzed stoichiometric reactions proceeded quantitatively in the solid state to give only one product (plus water), with unsurpassed atom economy. If catalysis with HCl was tried, the results were inferior. If melt reactions were required it appeared
Singlet dioxygen formation in ozone reactions in aqueous solution
作者:Florinella Muñoz、Eino Mvula、Silvia E. Braslavsky、Clemens von Sonntag
DOI:10.1039/b101230o
日期:——
of tert-butyl alcohol as ˙OH scavenger). The pyrimidine nucleobases only yield O2(1Δg) when deprotonated at N(1). O2(1Δg) formation is also observed with hydrogen sulfide (15%), azide (17%), bromide (56%), iodide (12%), and cyanide ions (20%). The O2(1Δg) yield from the reaction of O3 with phenols and phenolates is typically around 20%, but may rise closer to 50% in the case of pentachloro- and pentabromophenolate
作者:Raffaele Saladino、Giorgia Botta、Michela Delfino、Ernesto Di Mauro
DOI:10.1002/chem.201303690
日期:2013.12.9
From outer space: Twelve meteorite specimens, representative of their major classes, catalyse the synthesis of nucleobases, carboxylic acids, aminoacids and low‐molecular‐weight compounds from formamide (see figure). Different chemical pathways are identified, the yields are high for a prebiotic process and the products come in rich and composite panels.