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1.
Using the phase transfer catalysis technique, a series of fluorinated acetals has been prepared, in basic medium, by action of dicholromethane on 2-mononfluorinated alcohols or 1-F-alkyl 2-fluoroethanols. The identification of these new acetals has been achived by the study cf their 1H, 19F NMR and their mass spectra. 相似文献
2.
Bohumil Dolensky 《Journal of fluorine chemistry》2003,123(1):95-99
Nucleophilic attack of azide on 2-bromo-3-fluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1a) in aprotic solvent occurs on the 2-position to give the 2-azido derivative (2a). Reduction of azide and removal of the trityl group produces β-fluorohistidinol (6a). Elimination of HBr from 1a followed by “FBr” addition to the resulting double bond gives 2-bromo-3,3-difluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1b). Nucleophilic attack of azide followed by reduction and removal of the trityl group, as for the preparation of 6a, gives β,β-difluorohistidinol (6b). Initial attempts, under a variety of conditions, to oxidize the fluorinated histidinol precursors to carboxylic acids have not been successful. 相似文献
3.
β,β-Dihalo- and β,β,β-trichloroamines, obtained by Lewis acid-promoted Petasis-type reaction of α,α-dichlorinated and α,α,α-trichlorinated imines or reduction of α,α-dihaloaldimines, were subjected to a reactivity study and turned out to be remarkably stable compounds. In general, only the bases KOtBu and NaOMe cause a 1,2-dehydrochlorination with formation of unsaturated α-chloroimines or unsaturated α,α-dichloroimines. Hydrolysis of the α-chloroimines with aqueous oxalic acid resulted in the formation of the corresponding unsaturated α-chloroketones. The reaction of simple β,β-dihaloamines with NaOMe and KOtBu generated 2-haloprop-2-enylmines and 2,2-dimethoxypropylamines. 相似文献
4.
《Tetrahedron: Asymmetry》2001,12(9):1303-1311
A highly efficient enantioselective preparation of a β-bromo-β,β-difluoroalanine derivative, a promising general precursor for optically active β,β-difluoroamino acids, is described. Alkylation of the hydroxypinanone glycinate Schiff base 2a with CF2Br2 resulted in the production of undesired dehydrobrominated product 4a promoted by the lithium alkoxide moiety on the hydroxypinanone chiral auxiliary. Dehydrobromination was prevented by protection of the hydroxyl group on the chiral auxiliary. Utilization of TMSOTf resulted in production of (S,S,S,S)-3b as the sole diastereomer without dehydrobromination. Further transformations of (S,S,S,S)-3b to other optically active β,β-difluoroamino acids were demonstrated. 相似文献
5.
The reaction of β-oxodithioesters with the Vilsmeier-Haack reagent prepared from POCl3 and DMF provide β-chloro, β-methylthio α,β-unsaturated ketones in good yields. 相似文献
6.
7.
S Li K Huang B Cao J Zhang W Wu X Zhang 《Angewandte Chemie (International ed. in English)》2012,51(34):8573-8576
Building the building blocks: A highly enantioselective hydrogenation of β-aryl-β-alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomerically pure nitroalkanes 2, which are versatile precursors for chemical synthesis. 相似文献
8.
The combination of Fe(OTf)(2) and novel phenanthroline ligands enables the catalytic asymmetric epoxidation of acyclic β,β-disubstituted enones, which have been a heretofore inaccessible substrate class. The reaction provides highly enantioenriched α,β-epoxyketones (up to 92% ee) that can be further converted to functionalized β-ketoaldehydes with an all-carbon quaternary center. 相似文献
9.
10.
Conclusions ,-Bis(trifluoromethyl)glycidic ester is far more active than ,-dimethylglycidic ester and is opened by amines on the side of the -carbon atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8 pp. 1529–1530, August, 1964 相似文献
11.
Baylis-Hillman alcohols are excellent sources of the allylic halides ArCHCH(CH2X)(CO2R) (X=Br, Cl; R1=Me, Et, But). The Z double bond isomers are attained in high isomeric purity (>14:1, Z/E). The halides are chemo- and regiospecifically transformed into the acrylates (ArCHR2)C(CH2)(CO2R1) on treatment with Zn(R2)2 (R2=Me, Et, CH2TMS, CH2SiMe2OMe) or PrZnBr in the presence of catalytic amounts of copper(I) salts (0.5-20 mol%) in high yield. 相似文献
12.
A. Yu. Volkonsky V. R. Polishchuk E. M. Kagramanova E. I. Mysov N. E. Mysova M. Yu. Antipin Yu. T. Struchkov 《Russian Chemical Bulletin》1994,43(1):80-83
The 1:1 adducts of diethyl and ,,','-tetrakis(trifluoromethyl)divinyl ether (1),i.e., 3,5-(ee)-bis[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]-2,6-dimethyl-1,4-dioxane (2) (3 isomers) and 4-ethoxy-1,1,1-trifluoro-2-trifluoromethyl-3-[3,3,3-trifluoro-2(trifluoromethyl)propenyloxy]pentane (3), have been obtained by UV-irradiation of a solution of divinyl ether1 in diethyl ether. The X-ray structural investigation of the all-(e)-isomer of dioxane (2) has been carried out.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 85–88, January, 1994. 相似文献
13.
Abstract The reaction of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranose with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl trichloroacetimidate in CH2Cl2 promoted by BF3;OEt2 gives β,β-octaacetyltrehalose in up to 58% isolated yield, which is readily deacetylated to β,β-trehalose. The corresponding 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl penta-fluorophenylimidate is configurationally stable and inert to coupling under mild conditions. 相似文献
14.
A rhodium-catalyzed 1,4-addition of sodium tetraarylborates to β,β-disubstituted α,β-unsaturated esters has been developed. Highly efficient asymmetric catalysis has also been described to create quaternary carbon stereocenters at the β-position of esters by tuning the ester group of substrates and employing a readily available chiral diene ligand. 相似文献
15.
R. Riemschneider 《Monatshefte für Chemie / Chemical Monthly》1951,82(4):600-606
Zusammenfassung Unter Verwendung derGrignardschen Reaktion wurden aus 2,4-, 2,5-und 3,4-Dichlor-jodbenzol und Chloral die entsprechenden ,,-Trichlor--[dichlor-phenyl]-äthanole synthetisiert und als Acetate charakterisiert. Das ,,-Trichlor--[3,4-dichlor-phenyl]-äthanol (IV) läßt sich schneller und in besserer Ausbeute aus dem Produkt der Umsetzung von o-Dichlorbenzol mit Chloral in Gegenwart von Aluminiumchlorid isolieren. IV besitzt insektizide Wirksamkeit (Testtiere: Drosophila melanogaster, Blatta orientalis, Phyllodromia germanica, Calandra granaria, Acanthoscelides obtectus, Musca domestica). 相似文献
16.
An unusual oxidative palladium-catalyzed rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones is described. The geometry of the alkene product is not determined by the electronic nature of the aryl substitutents but rather is determined by substitution pattern on the aryl rings. The reaction proceeds in good yields, utilizes oxygen at atmospheric pressure as the terminal oxidant, and tolerates a variety of functional groups on the aryl rings. 相似文献
17.
WANG Jin-Xin ZHANG Chao-Xin LI Ying 《有机化学》2003,23(Z1):461-461
Chiral β-hydroxyl-γ-butyrolactones have attracted substantial interest in recent years due to their presence inmany strongly active natural products having antitumor, fungicidal, anti-inflammatory activity, and their use as important precursors in natural product synthesis. [1] In the course of the total synthesis of the natural product Tuxpano lide ,[2] we found a concise and efficient strategy on the stereocontrolled synthesis of β-hydroxyl-γ-butyrolactonederivatives from cheap and achiral starting material. 相似文献
18.
A type of porphyrin-chlorin heterodimers have been synthesized in a one-pot reaction, and their porphyrin and chlorin moieties are directly β,β'-linked through an sp(3) carbon. These species have been characterized by mass spectroscopy, (1)H NMR, X-ray crystallography, cyclic voltammetry, UV-vis and fluorescence spectroscopy. 相似文献
19.
The radical addition reactions of α-substituted β,β-difluorovinyl sulfones 1 with α-oxy and acyl radical species, such as 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, butanal and hexanal, afforded radical addition products 2--16 in good yields. 相似文献
20.
Yamada K Konishi T Nakano M Fujii S Cadou R Yamamoto Y Tomioka K 《The Journal of organic chemistry》2012,77(13):5775-5780
Dimethylzinc-mediated radical conjugate addition reaction of dimethyl alkylidenemalonates with iodomethyl pivalate gave a high yield of the α,β-dual oxymethylation product in one pot under air and the β-pivaloyloxymethylation product under argon. 相似文献