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1.
Identification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC-MS (gas chromatography-mass spectrometry) without reference substances. In this study a GC-FTIR-MS system (gas chromatography-Fourier transform-mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation. A combined GC-FTIR-MS system with a wide band (4000–550 cm?1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands. In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from C? H out-of-plane (oop) bending: for both the FAME and DMOX derivatives cis-1,2-disubstituted double bonds give a strong band near 720 cm?1 and the corresponding trans isomers near 967 cm?1. cis Isomers could be identified further by a band at 3012 cm?1. With the combined data of the GC-FTIR-MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers.  相似文献   
2.
Disclosed herein is an efficient Ag-catalyzed 4+1 heteroannulation reaction of enamides with α-carbonyl sulfoxonium ylides.The diastereoselective transformation provides a practical access to a diverse range of multi-functionalized oxazoline derivatives.The synthetic utility of the resultant tetrasubstituted oxazolines is further demonstrated by a series of useful manipulations into valuable building blocks of pharmaceutical relevance.  相似文献   
3.
Bis(oxazolines) and 2-(2-phosphinoaryl)oxazolines derived from highly enantiopure 2-amino-2-ferrocenylethanol have been tested as ligands in the asymmetric Pd(0)-catalysed allylic alkylation reaction. Essentially complete enantioselectivity (99.8:0.2 er) has been achieved in the nucleophilic substitution of 1,3-diphenyl-2-propenyl acetate by dimethyl malonate anion. The absolute configuration of the ligands has been unambiguously established by chiroptical methods.  相似文献   
4.
12-Tungstophosphoric acid (TPA) supported on silica, activated carbon and poly(4-styrylmethyl)pyridinium chloride (PMP) were found to be highly efficient catalysts for the synthesis of oxazolines, imidazolines and thiazolines from the condensation of various nitriles with aminoalcohols, ethylenediamine and cisteamine, respectively. In the case of oxazolines, dicyanobenzenes were selectively converted to mono- and bis-oxazolines in the presence of these catalysts. In the reaction of dicyanobenzenes with ethylenediamine, only mono-imidazolines were produced and the remaining cyano group did not react even with long reaction times. In the case of thiazolines, only bis-thiazolines were produced in the reaction of dicyanobenzenes with cysteamine. Furthermore, these catalysts could be recovered and reused without significant loss of their activities.  相似文献   
5.
(R)-4-Ethyl-2-(1,1-dimethylpropyl)-2-oxazoline (1) and (S)-4-tert-butyl-2-(1,1-dimethylbutyl)-2-oxazoline (2) were synthesized in two steps from the corresponding enantiopure amino alcohols and acid chlorides in a total yield of 95% and 72%, respectively. (S)-2-(1-Adamantyl-1-methylethyl)-4-isobutyl-2-oxazoline (3) was obtained from adamantyl bromide and l-leucinol in five steps in a total yield of 82%. Reactions of oxazolines 13 with Pd(OAc)2 in AcOH or CH2Cl2 followed by treatment with LiCl afforded the corresponding μ-Cl dimeric cyclopalladated complexes 15, 17, and 20 in good yield. Compounds 15, 17, and 20 reacted with PPh3 to furnish the corresponding mononuclear complexes 16, 19, and 21. The 31P NMR spectra of trans(N,P) adducts 16, 19, and 21 contained signals of two diastereomers in a ratio of ca. 1.3:1.  相似文献   
6.
Reactions of 4-alkylamino-2-phenyl-2-oxazolines 1 with isocyanates and isothiocyanates provide unprecedented efficient and regioselective heterocycle-heterocycle transformations. Compounds 1 reacted rapidly with tosyl isocyanate yielding directly 3-alkyl-4-benzamido-1-tosyl-2-imidazolidinones 4 in almost quantitative yields. The corresponding ureido intermediates 2 were not isolable species. However, the reactions with non-sulfonylated isocyanates or isothiocyanates were slower, leading to the expected ureido and thioureido derivatives 5, which were easily and efficiently transformed to either polysubstituted 2-imino-1,3-oxazolidine or 2-imino-1,3-thiazolidine hydrochlorides 7, respectively, by treatment with hydrochloric acid. The possible reasons for this disparity in chemical behaviour are discussed. X-ray crystallographic structures for 4-benzamido-3-methyl-1-tosyl-2-imidazolidinone 4b, 4-[1-isopropyl-3-(4-nitrophenyl)ureido]-2-phenyl-2-oxazoline 5e, (Z)-3-benzyl-4-benzamido-2-phenylimino-1,3-oxazolidine hydrochloride 7a and (Z)-3-benzyl-4-benzamido-2-phenylimino-1,3-thiazolidine hydrochloride 7b have been determined.  相似文献   
7.
A simple and short method for the reaction of methyl isocyanoacetate with aldehydes and N-sulfonylimines is presented. The reaction is catalyzed by copper(I) complexes and proceeds with excellent yields and high diastereoselectivities.  相似文献   
8.
A series of unique bicyclic aminooxazolines were synthesized and found to exhibit micromolar inhibition of β-secretase-1 (BACE-1). The aminooxazolines were procured by an intramolecular diethylaminosulfur trifluoride (DAST)-mediated ring closure of a benzylic urea onto a secondary alcohol.  相似文献   
9.
Lukas Werner 《Tetrahedron》2010,66(21):3761-3928
Conjugated dienes were converted to 1,2-oxazines by reaction with an acyl nitroso dienophile. The oxazines were reduced to 1,4-N-acetylamino alcohols, which were rearranged to the corresponding oxazolines upon treatment with methanesulfonyl chloride or anhydride. The oxazolines yielded 1,2-N-acetylamino alcohols upon hydrolysis. Thus either 1,4- or 1,2-N-acetylamino alcohols are available from 1,3-dienes via this methodology. Experimental and spectral data are provided for all new compounds.  相似文献   
10.
A new series of modular chiral selenium-containing oxazolines has been synthesized from inexpensive and commercially available l-serine and l-aspartic acid. These new compounds were evaluated as chiral ligands in the palladium-catalyzed asymmetric allylic alkylation reaction, furnishing the product in high enantiomeric excess, using Cs2CO3/CH2Cl2 as the base/solvent system.  相似文献   
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