排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
2.
3.
All-cis cyclitols derived from cyclopentane have been prepared in two ways: (i) by LiAlH4 reduction of all-cis epoxypolyos; (ii) by dimethyl sulfoxide treatment, in the presence of sodium hydrogencarbonate, of brominated derivatives containing a neighbouring benzoyloxy group; under these conditions, the halogen is replaced by a cis-oriented hydroxyl group. Thus all-cis cyclopentane-tetrol and -pentol have been prepared; their configuration has been confirmed by NMR. spectroscopy. 相似文献
4.
Low resolution mass spectra of cyclohexane-triols, -tetrols, -pentols and -hexols and of some of their deuterium labelled derivatives have been measured. The results indicate that for some geometrical isomers quantitative differences between ion intensities are significant, allowing to deduce the stereochemistry of the molecule from its mass spectrum. In all these compounds the electron impact induced elimination of water occurs mainly by interaction between OH groups. There is a correlation between the relative abundance of (M – H2O)+ and (M ?2 H2O)+ ions and the number of axial hydroxyls in the more stable conformation of the molecule. Difficulties encountered in deducing fragmentation patterns, and determination of number and position of deuterium atoms in the molecule of ms-inositol are discussed. 相似文献
5.
Bis(trifluoroalkylsulfonylimino)trifluoromethanesulfonic acid has demonstrated remarkable catalytic ability in the electrophilic acylation of aromatic substrates. Various perfluoroalkyl substituted aroyl chlorides are employed in Friedel-Crafts acylation typically using 1 mol % of catalyst. 相似文献
6.
The synthesis of a series of keto derivatives of cyclopentane is described. The configurations of these derivatives have been determined by chemical methods and verified by IR. and NMR. spectroscopy. The preferred conformation of the cyclopentane part of the molecule has been established by the study of intramolecular hydrogen bonds and the values of the coupling constants JH? C? OH and JH, H. 相似文献
7.
New simplified syntheses of two natural p-diquinonic pigments, phoenicine and oosporeine, have been described. By similar procedures, the syntheses of two other related diquinones have been carried out: 3,3′,6,6′-tetrahydroxy-biphenyl-di-p,p′-quinone and 3,3′,6,6′-tetrahydroxy-4-methyl-biphenyl-di-p,p′-quinone. The latter structure had been assigned to pyxiferine, which had been reported to be contained in the lichen Pyxine coccifera. 相似文献
8.
9.
Florea G. Cocu Batrice Pochelon Andr Giddey Thodore Posternak 《Helvetica chimica acta》1974,57(7):1974-1987
On treatment with higher diazoalkanes, 2,4,6/3,5-penta-acetoxy-cyclohexanone (penta-O-acetyl-myo-inosose-2 or -scyllo-inosose) afforded by ring expansion all-trans-penta-acetoxy-C-alkyl-cycloheptanones, which by deacylation were converted to hemiacetals. The reactions with diazoalkanes of the penta-acetoxy-inosose in the presence of aluminium chloride and of the free inosose in water solution have also been studied. The structure, the configuration, and, in some cases, the conformation of the new compounds have been established and some of their reactions have been investigated. The mechanisms of formation of the ring expansion products and of the concomitant spiro-epoxides have been discussed. 相似文献
10.
Friedel-Crafts bimolecular cyclizations of cinnamic acid and cinnamoyl chloride with aromatic compounds in strong and superstrong acids in present of 1 mol% BTISA were investigated. It was demonstrated that catalytic amounts of this new superacid have essential effect on such type of reactions. Its use makes possible the preparation of indanones with quantitative yields. 相似文献