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1.
Sonia Torrico-VallejosMauricio F. Erben Evamarie Hey-HawkinsCarlos O. Della Védova 《Tetrahedron letters》2011,52(41):5352-5354
Convenient simple and suitable methods for the synthesis of carbamates, N,N′-unsymmetrically disubstituted ureas, and S-alkyl thiocarbamates derived from CH3OC(O)SNCO in one-step are provided. Reactions are operationally simple and have high selectivity toward nitrogen, oxygen, and sulfur nucleophiles. The absence of solvents coupled with high yields and short reaction times make these procedures very attractive for synthesis. 相似文献
2.
Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N′-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the ‘imidazolium’ effect. Kinetic studies on the base promoted hydrolysis of both carbamoylimidazoles and carbamoylimidazolium salts reveal over a hundred-fold rate acceleration. The salts react with amines, thiols, phenols/alcohols, and carboxylic acids in high yields, without the need for subsequent chromatographic purification of the products, producing ureas, thiocarbamates, carbamates, and amides, respectively. Analogous thiocarbamoylimidazolium salts were also synthesized from secondary amines and N,N′-thiocarbonyldiimidazole (TCDI), followed by methylation with iodomethane. 相似文献
3.
Mustafa Eskici Abdullah KaranfilM. Sabih Özer Cengiz Sar?kürkcü 《Tetrahedron letters》2011,52(48):6336-6341
A synthetically useful level of reactivity of cyclic sulfamidates toward acetylides is described. Ring-opening reactions of a structurally diverse set of 1,2- and 1,3-cyclic sulfamidates with a range of lithium acetylides from aliphatic, cyclic, aromatic, heteroaromatic, and functionalized alkynes proceed smoothly in a regioselective manner to give the corresponding N-sulfate intermediates. Hydrolysis of these intermediates under acidic conditions furnishes the alkynylated amines in yields ranging from 29% to 98%. The scope of the acetylenic substitution reaction with the structural variations in both the cyclic sulfamidates and alkynes is briefly examined. 相似文献
4.
Valeria Di Bussolo 《Tetrahedron》2007,63(11):2482-2489
The glycosylation of alcohols, phenol, and partially protected monosaccharides with the diastereoisomeric d-allal and d-galactal-derived N-nosyl aziridines 2α and 2β leads to the corresponding 4-N-(nosylamino)-2,3-unsaturated-α-O- (6α) and β-O-glycosides and disaccharides (6β), respectively, in a stereospecific substrate-dependent O-glycosylation process. The N-(nosylamino) group of 6α and 6β can easily be deprotected to give the corresponding 4-amino-2,3-unsaturated-O-glycosides 7α and 7β, with an increased value to our glycosylation protocol. 相似文献
5.
Potenzo Giannoccaro 《Journal of organometallic chemistry》1994,470(1-2):249-252
The reactivity of mono- and di-methoxycarbonyl complexes of palladium of formula [PdL2Cl2-n(COOCH3)n] (n = 1 or 2; L2 = chelating ligand) towards amines in the presence of [RNH3]Cl or CuCl2 has been studied. The reactions yield N,N′-disubstituted ureas or carbamates, respectively. These results are compared with the dioxygen-induced carbonylative oxidation of amines catalyzed by palladium-based systems. 相似文献
6.
Gialih Lin 《中国化学会会志》2004,51(2):423-429
Substituted phenyl‐N‐butyl carbamates ( 1 ) and p‐nitrophenyl‐N‐substituted carbamates ( 2 ) are characterized as “pseudo‐pseudo‐substrate” inhibitors of acetylcholinesterase. Since the inhibitors protonate in pH 7.0 buffer solution, the virtual inhibition constants (Ki's) of the protonated inhibitors can be calculated from the equation, ‐logKi' = ‐logKi ‐ pKa + 14. The ‐logKi' and logkc values for acetylcholinesterase inhibitions by carbamates 1 correlate with the Hammett equation (log(k/k0) = ρσ); moreover, those by carbamates 2 correlate with the Taft equation (log(k/k0) = ρ* σ*). With modified Hammett‐Taft cross‐interaction variations, multiple linear regressions of the ‐logKi' and logkc values of carbamates 1 and 2 give good correlations, and the cross‐interaction constants (ρXR) are 0.5 and 0.0, respectively. The ρXR value of 0.5 indicates that the carbamate O‐C(O)‐N‐R geometries for the transition states that lead to enzyme‐carbamate tetrahedral intermediates are all pseudo‐trans conformations. Therefore, the carbamate moiety of the inhibitors stretches along the active site gorge of the enzyme but does not bind in the acyl binding site pocket of the enzyme. Overall, the carbamate O‐C(O)‐N‐R geometries for carbamates 1 and 2 , protonated carbamates 1 and 2 , and the tetrahedral intermediate are all retained in pseudo‐trans conformations. The ρXR value of 0.0 suggests that the transition states that lead to the carbamyl enzymes are breaking C‐O bonds and are excluding the leaving groups, substituted phenols. 相似文献
7.
《Tetrahedron letters》2004,45(21):4081-4084
β-d-Gluco and mannopyranosyl selenoureas have been prepared by coupling of the corresponding glycosylamines with phenyl isoselenocyanate in aqueous pyridine. Alkyl and aryl isoselenocyanates, and 1,4-phenylene diisoselenocyanate have been obtained from the corresponding formamides with an excess of triphosgene, black selenium and triethylamine. Treatment of the O-unprotected β-d-glucopyranosyl selenourea with aqueous oxygen peroxide afforded a 1,2-trans-fused bicyclic isourea. 相似文献
8.
The global and local electrophilicity indexes have been used to characterize the reactivity pattern of the CC double bond towards nucleophilic addition reactions. A wide family of molecules including ketones, esters, anhydrides, nitriles and nitrocompounds containing appropriate substitution on the CC double bond have been classified within an unique scale of reactivity. The predictive capability of the theoretical model is tested against a series of benzylidenemalononitriles and substituted α-nitrostilbenes. 相似文献
9.
M. Nasr H. H. Zoorob A. Zayed M. T. El-Wassimi 《Monatshefte für Chemie / Chemical Monthly》1979,110(4):913-918
Condensation of 4-bromomethylquinoline derivatives1 a-1 c with glycine and thioglycolic acid gave the corresponding quinolylmethylglycine and quinolylmethylthioacetic acid derivatives2 a-2 c and2 d-2 f, respectively. Cyclization of2 a-2 f was affected either by polyphosphoric acid or concentrated sulphuric acid to give3 a-3 f. Chlorination of2 a-2 f and3 a-3 f were also accomplished.
Die Reaktivität von 4-Brommethylchinolin-Derivaten gegenüber Glycin und Thioglycolsäure. Ein neues Ringsystem
Zusammenfassung Die Reaktion von 4-Brommethylchinolin-Derivaten1 a-c mit Glycin und Thioglycolsäure gab die entsprechenden Kondensationsprodukte2 a-c und2d-f.2 a-f konnten mit Polyphosphorsäure bzw. mit konzentrierter Schwefelsäure zu Benzo[c]-2,6-naphthyridinen3 a-f zyklisiert werden.2 a-f und3 a-f waren einer Chlorierung (POCl3) zugängig.相似文献
10.
Dipravath Kumar Seth 《Journal of organometallic chemistry》2011,696(23):3779-3784
The 4-R-benzaldehyde thiosemicarbazones (L-R) are known to react with [Rh(PPh3)3Cl] in refluxing ethanol in the presence of a base (NEt3) to afford organorhodium complexes (2-R), where the thiosemicarbazones are coordinated to rhodium as tridentate CNS donors with the sulfur atom oxidized by aerial oxygen to sulfone. Two triphenylphosphines and a hydride are also coordinated to the metal center. From the reaction with 4-nitrobenzaldehyde thiosemicarbazone, a second organorhodium complex (1-NO2) is obtained, in which the sulfur atom is not oxidized. Reaction of the 4-R-benzaldehyde thiosemicarbazones with [Rh(PPh3)3Cl] in refluxing ethanol in the absence of NEt3 affords another group of organorhodium complexes (3-R), in which the thiosemicarbazones are coordinated to rhodium as tridentate CNS donors, along with two triphenylphosphines and a chloride. In these 3-R complexes also the sulfur atom is not oxidized. Structures of all the complexes have been optimized by DFT calculations and compared with the already known X-ray crystallographic structures. Also the experimentally observed electronic absorption bands have been assigned to specific transitions based on the TDDFT studies. Molecular electrostatic potential (MESP) topographical analysis performed to find the deepest MESP point on the coordinated sulfur atom (Vmin) is used as a probe for assessing the oxidizability of the coordinated sulfur in 1-R and 3-R complexes. Energy differences between the three sets of complexes have been estimated and based on the results obtained, 3-R has been experimentally transformed into 2-R, via formation of 1-R as the intermediate. 相似文献
11.
Z- and E-isomers of 2-benzamido-3-phenylacrylohydrazide 2a, 2b have different relative reactivities towards some carbon electrophiles had been discussed.The Z-isomer underwent cyclization to give imidazole derivative 3 and triazine derivative 4, whereas the latter E-isomer does not undergo such cyclization. The reaction of 2a and/or 2b with 1,2-dibenzylidene hydrazine at different reaction conditions afforded the Schiff bases 6, 8 and the triazolidine derivative 9. Reactions of 2a, 2b with formic acid and phthalic anhydride gave the different cyclization products 10–14, respectively. The structures of all the new synthesized compounds were established from their IR, 1H-NMR and mass spectra as well as elemental analyses. 相似文献
12.
A thorough product analysis of the reaction of ascomycin with diazomethane has been performed. Apart from the expected oxiranes (epimeric at C9), a whole range of novel derivatives bearing various modifications in the binding domain were obtained. Proposed mechanisms for their formation and stereochemical aspects are discussed. 相似文献
13.
A. Rykowski E. Wolinska H. C. van der Plas 《Chemistry of Heterocyclic Compounds》2001,37(11):1418-1423
The reactions of 3-X-6-phenyl-1,2,4-triazines (X = SMe, SPh, SO2Ph) with phenylacetonitrile anion in DMF were studied. In these reactions the ring transformation product 3-amino-4,6-diphenylpyridazine, the covalent addition product 3-X-5-(-cyanobenzyl)-6-phenyl-2,5-dihydro-1,2,4-triazine, and the ipso-substitution product 3-(1-cyano-1-phenylmethyl)-6-phenyl-1,2,4-triazine were obtained. Analogous reactions carried out in DMA gave only the addition products in excellent yields as diastereomeric mixtures of the corresponding 2,5-dihydro-1,2,4-triazines. 相似文献
14.
The reactivity of the free aluminylene [N]-Al ( 1 ) ([N]=1,8-bis(3,5-di-tert-butylphenyl)-3,6-di-tert-butylcarbazolyl) towards boron Lewis acids is investigated. A facile oxidative addition reaction of 1 with Ph2BOBPh2 furnishes an exceedingly scarce example of the free alumaborane [N]-Al(BPh2)(OBPh2) ( 2 ) with an Al−B electron-sharing bond. By contrast, complexation of 1 with B(C6F5)3 and HB(C6F5)2 gives rise to the corresponding Lewis adducts [N]-Al→B(C6F5)3 ( 3 ) and [N]-Al→BH(C6F5)2 ( 4 ), respectively, with an Al→B dative bond. Crystallization of 4 in Et2O produces the adduct [N]-Al(Et2O)→BH(C6F5)2 ( 5 ). Quantum chemical calculations are carried out to understand the formation of 2 as well as the bonding situation of 3 and 5 . 相似文献
15.
Michael Knorr Isabelle Jourdain Carsten Strohmann 《Journal of organometallic chemistry》2005,690(6):1456-1466
Insertion of hexafluorobutyne into the Pt-H bond of the heterobimetallic complexes [(OC)3Fe{Si(OMe)3}(μ-Ph2PXPPh2)Pt(H)(PPh3)] (1a X = CH2; 1b X = NH) yields the σ-alkenyl complexes [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-Ph2PXPPh2)Pt{C(CF3)C(H)CF3}] (3a X = CH2; 3b X = NH). This insertion reaction is accompanied by dissociation of the platinum bound PPh3 ligand and saturation of the vacant coordination site by a dative μ−η2-Si-O → Pt interaction. Addition of the Pt-H bond of 1a across the triple bond of 3,3,3-trifluoropropyne affords in a regiospecific manner [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppm)Pt{C(CF3)CH2}] (2) having the trifluoromethyl substituent on the α-carbon. Addition of RNC to 3 affords the isocyanide adducts [(OC)3Fe{Si(OMe)3}(μ-Ph2PXPPh2)Pt(CNR){C(CF3)C(H)CF3}] (4a R = t-Bu, X = CH2; 4b R = 2,6-xylyl, X = CH2; 4c R = 2,6-xylyl, X = NH). In dichloromethane solution 3a is gradually transformed into the C4F6-bridged compound [(OC)3Fe(μ-dppm)(μ-CF3CCCF3)Pt(CO)] 5. The Pt-bound carbonyl ligand of 5 is displaced by xylylisocyanide or trimethylphosphite affording the derivatives [(OC)3Fe(μ-dppm)(μ-CF3CCCF3)Pt(CNxylyl)] 6 and [(OC)3Fe(μ-dppm)(μ-CF3CCCF3)Pt{P(OMe)3}] 7. The molecular structures of 4a, 5 and 6 have been determined by X-ray diffraction studies. 相似文献
16.
Kinetic data for the oxidation of glutathione (reduced, GSH), cysteine, glycine and glutamic acid by colloidal manganese dioxide,
(MnO2)
n
are reported. Colloidal MnO2, oxidized glutathione to disulphide (glutathione, oxidized), was reduced to manganese (II). Glycine and glutamic acid (structural
units of glutathione) are not oxidized by colloidal MnO2, but the other structural unit, cysteine, is also oxidized by the same oxidant under similar experimental conditions. This
is interpreted in terms of the rate-determining colloidal MnO2-S bonded intermediate. The reactivity of GSH towards colloidal MnO2 is very much higher than cysteine. Kinetics of oxidation of GSH and cysteine by colloidal MnO2 were performed spectrophotometrically as a function of [GSH], [cysteine], colloidal [(MnO2)
n
], [HClO4], temperature and trapping agents sodium fluoride and manganese (II) (reduction product of colloidal MnO2). The purpose of this work was to study the role of –NH2, –COOH, –SH groups present in the carbon chain of the above amino acids. It was found that the reactivity of –SH group is
higher than –NH2 and –COOH groups. The mechanisms, involving a colloidal MnO2 complex with GSH and cysteine, are proposed. The complexes decompose in a rate-determining step, leading to the formation
of free radical and manganese (III), which is also an intermediate. The dimerization of radicals takes place in a subsequent
fast step to yield the products. 相似文献
17.
Jens Beckmann Dainis Dakternieks Andrew Duthie Naomi A. Lewcenko Cassandra Mitchell Markus Schürmann 《无机化学与普通化学杂志》2005,631(10):1856-1862
The reaction of (p‐MeOC6H4)2TeO with two equivalents of HO3SCF3 and HO2PPh2 provided the tetraorganoditelluroxanes (F3CSO3)(p‐MeOC6H4)2TeOTe(p‐MeOC6H4)2(O3SCF3) ( 1 ) and (Ph2PO2)(p‐MeOC6H4)2TeOTe(p‐MeOC6H4)2(O2PPh2)·2 Ph2PO2H ( 2 ) in good yields. Compounds 1 and 2 were characterized by solution and solid‐state 31P and 125Te NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, conductivity measurements and single crystal X‐ray diffraction. In solution, compound 1 undergoes an electrolytic dissociation and reversibly reacts with traces of water to give the mononuclear cation [(p‐MeOC6H4)2TeOH]+ and triflate anions. Theoretical aspects of the protonation and hydration of model telluroxanes R2TeO (R = H, Me, Ph) were investigated by preliminary DFT calculations and compared to the corresponding selenoxanes R2SeO. The tellurium dihydroxides R2Te(OH)2 seem to be more stable than the hydrogen‐bonded complexes R2TeO·H2O. 相似文献
18.
Bernd Wrackmeyer Elena V Klimkina Yuri N Bubnov 《Journal of organometallic chemistry》2003,687(1):108-117
1-Boraadamantane (1) and 2-ethyl-1-boraadamantane (1(2-Et)) react with bis(trialkylstannyl)ethynes (3), R3Sn-CC-SnR3 with R=Me (a), Et (b), in a 1:1 molar ratio by 1,1-organoboration under very mild conditions to give the 4-methylene-3-borahomoadamantane derivatives 4a,b and 7a,b, respectively, which are dynamic at room temperature with respect to deorganoboration. The compounds 4a,b react further with 3a,b by 1,1-organoboration to the tricyclic butadiene derivatives 5a,b. Attempts to crystallise 4a afforded the product of hydrolysis, the diboroxane 6a which was characterised by X-ray structural analysis. All products were characterised in solution by 1H-, 11B-, 13C- and 119Sn-NMR spectroscopy. 相似文献
19.
Inside Cover: Infrared Detection of Criegee Intermediates Formed during the Ozonolysis of β‐Pinene and Their Reactivity towards Sulfur Dioxide (Angew. Chem. Int. Ed. 3/2014)
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Jennifer Ahrens Philip T. M. Carlsson Nils Hertl Prof. Dr. Matthias Olzmann Mark Pfeifle Dr. J. Lennard Wolf Dr. Thomas Zeuch 《Angewandte Chemie (International ed. in English)》2014,53(3):602-602