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Reaction of Arylnitroso Derivatives: synthesis of Arylimino 2,5-Dihydrofuranand Arylamino Fulvenes Derivatives
Full text linkHerein we report the reactivity of N-(2,4-dicyano-1,5-dimethyl-3-arylcyclopenta-2,4-dienyl)-2,2,2- trifluoroacetamides and N,N-dimethyl-4-nitrosoaniline which provide compounds derived from Ehrlich-Sachs condensation, dihydrofuran derivatives and fulvene derivatives by adjusting the reaction conditions
Photochemical Rearrangements of 3-Methylisoxazolopyridines
No full textIrradiation in water-saturated ethyl ether of isoxazolopyridines 1a,e, beside the corresponding oxazolopyridines 2a,e, leads to N-methylcarboxamides 3a,e via 1-2 shift of the methyl group. The isoxazolopyridine 5, bearing a hydrazino group in 4-position, rearranges only to l-aminopyrazolopyridine 6. © 1988
2-Azabicyclo[4.2.0]octane derivatives: Stereoselective photochemical Synthesis and Chemical Reactivity
No full textPhotochemical addition of acrylonitrile to 1,4-dihydropyridines 1 and 2 followed by catalytic hydrogenation of the products gave trans-8- and trans-7-cyano-cis-2-azabicyclo[4.2.0]octane-6-carboxylates 6a, b and 8a, b; the corresponding cis 7b, 9 and trans 6b, 8b stereoisomers were both obtained from 1,4,5,6-tetrahydropyridine 4. Using the chiral 1,4-dihydropyridine 3, azabicyclo[4.2.0]-octanes 6c, 7c and 8c were obtained with an enantiomeric excess in the range 45-15%. Thermal cycloaddition of p-chlorobenzonitrile oxide on the same substrates yielded compounds 10 and 11, with site- and regio-selectivity but without stereoselectivity. Cyclobutane ring opening under basic or acid conditions was observed only for 8-cyano-2-azabicyclo[4.2.0]octane 6b which gave the 1,4,5,6-tetrahydropyridylpropionitrile 15 or the piperidine-2-ol 17
Reactivity of a Cyclic alpha-Bromoiminium Bromide towards Nucleophiles
No full textPiperidine‐pyrrolidine ring contraction of 1‐piperideinium bromide (1) was observed by reaction with aqueous bases, sodium methoxide, phenylhydrazine, (S)‐1‐phenylethylamine and sodium borohydride, whereas diazomethane addition mainly gave pyrrolo[3,4‐b]pyridine derivative 8. Some stereochemical features of these reactions have been investigated. 1 gave back bromine under suitable conditions. Copyright © 1987 Journal of Heterocyclic Chemistr
Flash Photolysis Study of 3-Methylisoxazolo[5,4-b]pyridine
No full textThe photoreactivity of the title compound has been examined in MeOH, PriOH, MeCN, and MeCN/as-dimethylhydrazine solutions. A ketenimine and a spiroazirine intermediate account for the final products as well as for the transients observed in the flash photolysis experiments. It is also found that acid catalysis plays an important role in the reaction of spiroazirine to oxazolopyridine. © 1990 American Chemical Society
The Photochemical Synthesis of Naphto[2,3-g]thiopheno[3,2-e]benzo[b]thiophene, a New Heterocyclic system
No full textA new polymer supported reagent for the synthesis of beta-lactams in solution
No full textA modified Mukaiyama reagent was prepared on a PS-DVB resin. This reagent was used for the preparation of β-lactams, using the Staudinger reaction. The products were obtained by generating the ketene from a carboxylic acid under sonication with the resin followed by reaction with the imine. Excess of the imine was removed by reduction followed by acid scavenging
Crystal and molecular structure of the ternary complex bis[(adenosine 5'-triphosphato)(2,2'-bipyridine)zinc(II)] tetrahydrate
No full textThe crystal structure of the dimeric species [Zn(II)-H2ATP-2,2′-bpy]2· 4H2O has been determined by X-ray diffraction. Cell constants are a = 11.105 (3), b = 25.223 (7), c = 10.539 (3) Å, β = 91.34 (4)°, with monoclinic space group P21. Diffractometer collected reflections (1617) were used for the structure determination and refinement (R = 0.098). The structure of the compound consists of dimeric molecules in which two zinc atoms are held together by two -OPO- bridges from the γ-phosphate groups of two ATP molecules. Both zinc atoms show a distorted octahedral coordination formed by two oxygen atoms from different γ-phosphate groups, one oxygen atom from the β-phosphate group, and the two nitrogen atoms of the bipyridyl ligand. The sixth position is filled by a α-phosphate oxygen atom which is more weakly bound. The five closest Zn-N and Zn-O distances average respectively 2.14 (4) and 2.03 (3) Å. Both ribose rings show the common C3′ endo configuration. The conformation around the exocyclic C4′-C5′ bond is gauche+ for both rings. The structure is held together by strong intermolecular bipyridyl-purine and bipyridyl-bipyridyl stacking interactions. Weaker bipyridyl-purine intramolecular stacking is also observed. The molecule provides a possible model for ATP transport and phosphate group transfer mechanism. © 1981 American Chemical Society
Trapping of photochemical intermediates as a tool in organic synthesis. Preparation of spiroaziridinopyridones, a new heterocyclic system
No full textWhereas alkyl lithium and Grignard reagents both at rt and at -80°C thermally react with 3-methylisoxazolo[5,4-b]pyridine giving alkylation and/or isoxazole ring opening products, sodium malonate and sodium boron hydride react only under UV irradiation. Selective trappings of ketenimine or azirine intermediates give an enaminopyridone or two diasteroisomeric spiroaziridinopirydones. Regioselective opening of the aziridine ring with perchloric acid gives 3(1-amino-ethyl)-1H-pyridin-2-one. © 2002 Elsevier Science Ltd. All rights reserved
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